Shop-bot software and Geckos

[bleeth]

I just got done spending the day with Dirk Hazelberger rebuilding (ok-watching him rebuilding) my PRT control box with his Gecko drivers board running SB Alpha software and running some tests with my previously stock PRT w/ 5hp Columbo purchased shortly before the Alpha came out. We ended up upgrading my power supply also to a 70 watt system and because my serial port in my stock computer couldn't communicate fast enough with the controller, used a USB adapter to enhance that part of the operation. We did put a high speed serial port card in my computer (a Dell running xp at around 1.67 MH with 512Ram) but had difficulty getting the software to load properly due to a malfunctioning cd drive and so fell back on the USB adaptor for now which actually classifies as the minimum you can go and get effective results.
My jog speed is now 8ips from a previous 3 to 3.5. That was nothing short of thrilling. It was more thrilling when Dirk hooked up his own computer that had the Serial card installed and running smoothly and we were jogging at 16ips plus without losing a single step. To test this I bored a hole in my test board (3/4" virola) and we ran a jogging loop program that took my router all over the table in a zig-zag path for 5-7 minutes and when I returned to the hole it was dead on accurate. I can also tell you that it was running smoother than I had ever experienced before.

The next test was cutting. For this test I ran a part file in the same 3/4" ply that I had run before for a work project using the latest PRT software with a 1/2" carbide compression bit that we had set up to cut at 2.0 ips in two passes.

We steadily increased the speed and lost steps at around 3ips in the y direction. After raising the bit and turning the motors off we determined that the movement of the y car felt more restrictive at the point where the motor lost steps. I feel that a re-squaring of the y-axis and adjusting of the rails (I think my right hand rail has a bit of a curve to it) may allow that 3.0ips to happen, but even with the previous software and controller I rarely cut critical parts faster than 1.5 simply due to deflection of the gantry at higher speeds and the fact that I am extremely picky about close tolerances in part cutting.

I believe, but cannot yet attest to, that with a stiffening of the current gantry by welding the corners and replacing the car with either an alpha "unibody" car or a custom design like Gerald's I will be able to achieve cutting speeds in a higher range through plywood or particleboard and that the current limits are more due to structural challenges than any other cause.
In addition to the somewhat enhanced cutting speed and the highly enhanced jog speed I can also tell you that the smoothness of the cut, even with such a value priced product as virola ply was fantastic on cuts in the x axis, y, axis, small diameter curves, and large diameter curves.

Bottom line is I am fantastically impressed with the improvements made without the requirements to either change out my motors or abandon the SB software I am so used to and appreciate so much.

The improving of the stiffness of the car and gantry, which I figured I would end up having to do before I took this step, is still an important part of the upgrade process but, as a first step, I am truly pleased with the results so far.

I will post a further update to this when the high speed serial card is operating. In the meantime-color me happy: My bot is finally moving closer to the way I thought it should when I bought it.

Dave

[benchmark]

Hi Dave

What is the reason for running a PRT with the SB Alpha software? ..... the 16" jog sounds interesting

Regards

Paul

[bleeth]

Paul: In additon to the Gecko drivers and the increased voltage power supply, the other part of the upgrade is using a shop-bot supplied Alpha board as the platform. That of course requires the Alpha version of the software. This means that I can continue to use SB3 as my op system which personally, results in not having to become familiar with a different software. My thoughts on it probably parallel the idea that when I souped up my old Mustang I didn't want to put in a Chevy engine.

Dave

[joe]

Dave,

Good for you.

I've also seen a simular upgrade on the PRT improving cutting speed and cuts. Many of us have struggled with chatter marks and have spent endless hours making adjustments to solve the problem. Now with the upgrades, the machine cuts like the big boys, smooooth, very, very fast and competative cuts. Another quality is how quiet the gantry moves around the table.

Keeping the old PRT motrs is correct. There plenty powerful there. No need to change out.

Another inexpensive addition which extends quality is the Mach. With it you have on screen viewing of the cutting process along with many programing options far beyond the limits of the SB program. This program takes SB into the level of 60K units.

Although I haven't investigated all the upgrades, I've seen first hand the Ascension 1000 and it's amazing. It's a plug and play unit, that will drop your jaw. Really.

Joe

[jhicks]

All indications seem to point to a leap in technology which seems like a great plus for existing bot owners. Are these types of enhancements part of shop bot plans or future offerings?
I guess I would feel a bit more conforted knowing that the folks at shopbot are moving forward in these areas so we aren't left to our own adaptations and experimentation.
Regardless, it looks like exciting developments.

[mikejohn]

If you haven't yet done so, pop in to www.mechmate.com (http://www.mechmate.com) and see whats being discussed there.
Because of a spamming attack, you have to register to post.

................Mike

[gerald_d]

I have started to post downloadable plans for the MechMate gantry that Dave mentions above, but I first have take a few weeks holiday before I can finish posting them.

[bleeth]

My hopping up of my PRT this way at this time would be a moot point if I had by fortune or information waited just a few weeks to buy it since the Alpha came out very shortly after I took delivery of my PRT. Although that was a sticking point for me, I have had nothing but great customer service from and have nothing but the greatest admiration and respect for the entire crew at Shop-bot. The SB software works fine for me and so, now that I can afford to invest in enhancements for the bot I have chosen to go the way I am. I am sure that Ted is seeking more and better ways to improve the Shop-bot and I will probably lust after some of them at a later date. In the entire time I have owned it absolutely nothing has broken beyond the cable bow. Investing now to enhance it makes it no less a Shop-Bot to me. As the heading of this thread category says: It is for modifications and variations of ShopBots. If I thought there was a better product out there for the money I would buy it and be on their forum.

Joe: You are soooo right about the quietness and smoothness of the way it moves now. I love it.

Dave

[joe]

Dave,

Isn't it strange, the difference the sound a PRT makes with a upgrade. It's as though it's gliding on ice. With the Ascension 1000 (custom-cnc.com) you can toggle the X and Y at the same time at 14ips which means you can scoot down to the other end in seven seconds. While speed is important, the real test is in the quality of the cut. Thats where they excell.

Keep us informed about your progress.

J.

[dirk]

Hey Guys
I'm working on a website that will give all the details. I hope to have it finished by weeks end. I will also post a video on the site of the trip to Daves.
Dirk

[dirk]

I've posted a couple of pics and a video we took at Dave's shop. Here's the link.
http://www.botrods.com/Download1.html

[gerald_d]

A note to folk who are visiting a site that is under construction....Press the page refresh button on your browser to see the latest version of the page. Your PC might just be showing the older page from its cache.

[richards]

When I was down in Los Angeles today, I planned on picking up four steppers from Oriental Motors (PK296 with 3.6:1 gear ratio). However, their web site lists an ungeared motor at 22 lb*in holding torque and the 3.6:1 geared motor at 20 lb*in holding torque. I assumed that I should get at least 60 lb*in of torque. After a long conversation with the tech department, they told me that the small print for the 3.6:1 gear box limits the load to 20 lb*inches.

Has anyone run their stock PRT 3.6:1 motors long enough and hard enough with a Gecko driver to cause the gear box to fail?

[gerald_d]

20 lb*inches on a 1" diam pinion translates to 40 lb thrust at the tool tip - not bad for "average duty" or "continuous duty".

[richards]

Gerald is right about 40-lbs instead of 20-lbs - my math skills are horrible. A 1-inch pitch diameter is about 1/2-inch radius, which doubles the available torque.

How about backlash? Oriental Motor's tech department told me that I should expect about 1 to 2 degrees of backlash if I use their PK296B2A-SG3.6 motor. Doing the math shows that a 1-inch pitch diameter spur gear moves 3.14 inches per revolution. 3.14 divided by 360 gives 0.0087 inches movement per degree. Two degrees backlash would equate to 2 X 0.0087 inches, or 0.0174 inches of backlash. That is a little more that 1/64-inch.

Since the goal is to eliminate 'chatter', I'm wondering whether 0.0174 inches is going to matter, given the assumption that there has to be some backlash inherent in the rack and pinion.

Right now my two choices seem to be to either buy the stock Oriental Motor stepper motor with 3.6:1 spur gear built in or to build a belt driven reducer using XL timing gears (20 tooth on the motor and 72 tooth on the shaft) and timing belts. From past experience, I know that I can build a belt-drive with no back-lash (when properly tightened). The timing belt system would also have much higher torque than the stock Oriental Motor solution. The drawback is needing to have a machine shop build motor mounts, shafts, bearing blocks, and pulley hole enlargement. Good, accurate machine shop work would produce a gear reduction unit with tight specs. Sloppy machine shop work would give me something else. How about some advice from those of you who have some experience using either type of gear reduction?

[dirk]

Hi Mike
When you look at the alternatives the gear reducer/motor combination on the PRT becomes more of a bargain than you might think. Bolt on Gear reducers for 34 size motors with medium accuracy can run 500 or more apiece. This allows you to choose your motors but after you add the motors and reducers you may be looking at 2500 to 3000 to change out motors and drives.

The belt reduction works very well until you get into high ratios, then it can get pretty bulky. The reducers can be as simple or complex as you like. When SB started using rack and pinion they came up with a very simple setup that I think performs better than the standard gear motors being used. I built my own fashioned after theirs. I did most on a drill press and I used bronze bearings. I bought a sized ground piece of shaft from MSC and a chucking reamer that I used to get the bore on the bronze bearings right. I did the same on the pulleys and gear pinion. The belt reducer used a XL belt with a 3 to 1 ratio. The simplistic design of a belt reducer doesn’t require high precision machining like a gear reducer would

[richards]

Hi Dirk,
I think I'll try your suggestion and build a belt reducer. After rumaging through my junk pile, I found some 72 tooth gears, some 20 tooth gears, and some 1/2-inch shafts that were left over from other projects. The center of the 20-tooth gears is only 15/16-inch in diameter, but it should be large enough so that the shaft hole can be enlarged to 1/2-inch without compromising its strength.

To keep things really simple, I'll probably just mock up some mounting plates from 1/2-inch thick plastic. If I use shielded ball bearings on the shafts, there shouldn't be excessive heat - at least for the few hours that it would take to run 'chatter' tests.

If the 'chatter' is still there after adding a 3.6:1 reducer, then I suppose it would be time to take the Gecko stuff off the test bench and see if it works as a 'chatter' eliminator.

(I've heard lots of good things from people who've converted to Geckos and Mach software but so far no one has posted photos. It seems that a photo showing before and after shots would settle the issue once and for all. It's not that I don't trust what has been written, but the improvement that they write about, although it may be substantial, may be less than I would expect from a major modification to my machine.)

[garyb]

This one's for you Mike.
Cut on the Shopbot running the Ascension 1000 and Mach3 about an hour ago, taken off table and photographed as cut.
One past @ 2IPS 1/4" spiral up in 3/4" MDF

Sorry could not give before photo, SB software and controller removed from this system


401

[richards]

Gary,

Thanks! That's exactly what I always expected a CNC router to do - first time - every time.

Okay, Shopbot tech support, how can I get my Alpha to make cuts like those in Gary's photos?

[joe]

Good Cut Gary,

Mike, this is a no brainer with the Ascension 1000 which is armed with Mach 3.

Joe

[richards]

Joe,
The photo shows that the Ascension and Mach3 can do it, but this is still the SHOPBOT forum geared towards us guys that use factory equipment. I think that it's only fair that Shopbot have first dibs on upgrading their hardware (or marketing the Ascension and Mach3 as an option).

Quality of cut is important more often than not - at least in the work that I do. Until now, I've tried to tell myself that quality and low price don't go together - but the photo makes that statement a lie.

As a side note, I've been burning up the phone line between Salt Lake and Oriental Motor in an effort to buy stock stepper motors with gear boxes attached to increase the resolution of my machine. Their response is to buy new Alpha stepper motors with 5:1 gear boxes installed at $2,000+ per motor. So far they insist that the quality (no-backlash/high torque) gearboxes are not compatible with the PK series of motors. If I wanted to spend $8,000 - $10,000 to upgrade my machine, I'd remove the steppers entirely and install servo motors. In my opinion, $1,000 per motor/driver/gearbox is as high as I'll go for a stepper system. At $1,000 per motor/driver/gearbox, I would already be far into the brushed servo motor spectrum. At $2,000 per motor/driver/gearbox, I would be fully into the AC servo/driver/gearbox area.

[joe]

Mike,

I agree with your about this being a supportative Shopbot Forum and as a dedicated supporter, I've never, ever suggested a name of a competator. Never would.

This is a seperate product. It's a add-on-update. SB doesn't offer any updates for those old PR's, PRT's at this time. I'd just like seeing those old units running as fast as a Alpha and cutting better, for less that $2000. This will help SB not hurt her.

O yes. I don't own any part of Ascension 1000 or get a penny from them. Also I have no ego in this one.

The Shopbot motors are good enough. I'd leave them alone.

J.

[richards]

Joe,

You've found the important point. The cut was made (as far as I know) with the Ascension 1000 and Mach3 with GEARED 3.6:1 motors (as supplied with Shopbot) on many of their machines. I'm an owner of the Alpha model with direct drive motors (no gearing).

In order to get the quality of cut shown in the photo, it seems that I would have to do several things: 1. Buy the Ascension 1000 box; 2. Convert files to G-code to run with Mach3 software; and 3. (The most important point for me at the moment) remove the standard Alpha steppers and use a geared stepper motor (similar to the PK296A2A-SG3.6).

Since my business literally depends on getting the quality of cut shown in the photo, you can probably imagine how important it is to me to know exactly what I must do to get that quality.

Since my machine is the latest and greatest machine offered, and since my machine produces cuts the are significantly lesser in quality than the cuts shown in the photos, I'm just a little upset, having spent the better part of $20,000 to own something that gives a curved cut that is on par with the cut expected if I were to use a dull hacksaw, late at night with the lights out!

The subject of cut quality has been aired for well over a year on this forum with nothing being done to make the machine give a quality cut. I've followed every thread and tried every valid suggestion in an attempt to find the magic bullet that would turn my Alpha into a CNC machine that would give the quality of cuts that an owner of a CNC machine should expect. So far, nothing that I've tried has had much effect on the quality of cut.

Hopefully, Joe, you don't think that I'm attacking you or anyone else on this forum for your opinions or for your perferences. All that I'm trying to do is make my machine work like a real CNC router. If Shopbot can tune their controller(s) and software to duplicate the results shown in the photo, then, as far as I'm concerned, now is the time to do it. If, for any reason, the best minds and great talent available at Shopbot can't make their controller and software do what is shown in the photo, then wouldn't it be prudent to offer the Ascension, Mach3 and stepper motors/gear box, or something similar, as an option so that those of us who own the Alpha model can make our machines work?

This may sound awfully harsh, but, if time and materials are worth anything, I could have bought more than one $100,000 machine and still have change left over if I calculated the cost of trying to make my machine give a cut as smooth as the cut that I've always gotten on a router table.

[joe]

Mike,

The solution comes with the combination of a new controller and software. Souping up one or the other will not get the job done. It takes both.

The direct drive motors on the Alpha are also a problem. I believe Alan has a solution you might want to consider.

You're not alone. You are part of a dedicated community of Shopboters, working their way through these old problems. Changes are at hand.

Joe

[williamim]

I recently purchased the Ascension 1000 and MACH 3 software from Alan at Custom CNC.com. I am running the Ascension 1000 on a stock ShopBot PRT with a 1.00 MH computer and I did not have to upgrade my serial port. I am cutting ¾” plywood at 8 inches a sec. in two passes. I have also cut circles and 3D carvings and to my amazement none of these parts needed sanding. The photos you see on Alan’s web site are what I got!! I have seen more motor power, increased resolution and speed and since I installed the Ascension 1000. I have not lost connection with the controller nor have I had the Bot stop in the middle of a cut file this alone will save me money, time and frustration. The cost of the upgrade is less than half of an Alpha upgrade and I have none of the ShopBot software issues.

[gene]

William.
What was the total cost of the upgrade and what is involved in doing this? If you would rather not post it on the forum e-mail me . Thats if you are willing to tell such info. I too have the common chatter problem and would love a cure for this illness . Thanks Generhodes@concast.net (mailto:Generhodes@concast.net)

[pfulghum]

Joe,
Can you give some details on your statement

"The direct drive motors on the Alpha are also a problem. I believe Alan has a solution you might want to consider."

I would like to get my cut quality up on 20 tooth pinon direct alphas.

-- pat

[joe]

Howdy Pat,

It would be necessary to change out the Alpha motors when going with the Ascension 1000. You would be money ahead to bundle those motors and control box and sell it as an Alpha upgrade to a PRT owner, and purchase a Ascension-motor package.

What are you running now and what are your goals?

[joe]

Howdy Pat,

It would be necessary to change out the Alpha motors when going with the Ascension 1000. You would be money ahead to bundle those motors and control box and sell it as an Alpha upgrade to a PRT owner, and purchase a Ascension-motor package.

What are you running now and what are your goals?

[kerrazy]

[This has been posted on the mechmate forum as well]

Wow, Miss a spring, miss a lot.
What a flury of activity over new control hardware and UI.

I have just come back into both forums (talkshopbot and Mechmate) after being away for sometime due to personal reasons.

I had heard rumours last year that there was for lack of a better word, an underground movement to enhance our ShopBot cutting capabilities. Never did I expect to see what I am seeing.

A control box, either Dirk's or Alan's that could breathe new life back into our PRT and for some real old school folks PR machines.
Many of us were very disappointed when ShopBot came out with the new Alpha tool. Why? Because damn it, we now had a tool that we have in some occasions limped along with (this is not me, I have been very fortunate with my PRT) and ShopBot instead of offering us a unique tweak for our tool, decided to create a whole new tool with new Gantry, stiffer support for the table, new motors and control box.
I for one was very frustrated by this, and the frustration did not lie with ShopBot, no siree it was my own doing. I had convinced the group I was with at the time that this tool was the best bang for their buck and would last us for many years. And rightfully so it has. But we always want the new and improved tool right, otherwise we would still be using hand held screw drivers not have ( current count today 6 ) cordless drills.
The stretch in dollars and cents to upgrade to the new Alpha model was too hefty for me as well, because if you are going to do it then do it right, so this meant the new gantry and gussets and ah hell might as well get a spindle as well. Unfortunatley still not in the foreseeable future.

What shopbot has provided to all of us in the community is what I refer to as a "Popular Mechanics, 'do it yourself'" routing system. It is affordable, repairable and upgradeable. Very much like the 1950 and 60's popular mechanics articles on making your own space rocket on a weekend in your own garage.

That is why I bought this tool in the 1st place, I did not want to have to rely on someone to come and repair our tool if it required it and wait on their schedule to repair it. I could if need be get on the forum or contact ShopBot, and within a few minutes or hours start making dust again.

All this mindless banter is going some where so hang on....

The other neat thing about the ShopBot was its ease of modifcation, Over the last 4 years I have witnessed many discussions and pictures of modifications, From Brady's combo Plasma, Wood Router with extra Square tubing to lift his gantry, to Gerald's Motor mounting mods. Hell who remebers Ron V's crazy things too?

So I don't paticularly see the fuss over the New Control Hardware or UI offerings.
These are just one more component that make up the final tool. no different than a fellow bolting a dremel to his Z which we have all seen.

The end result of the machining phase ( the finished product ) consists of many components working together. 1.)CAD/CAM software powerful and intuitive enough to allow the user to create their part, the 2.)Controller UI, which effectivly interprets the CAM Post processor file, 3.)The control box to take the info and relay it to the motors, efficiently and accuratly, 4.)a sufficently strong enough gantry and table 5.) Fixturing your substrate 6.)cutter motor (router or Spindle[feed and speed]) and of course your 7.)selection of cutter.

of those seven variables that create a good finished product, we really have only relied on ShopBot for 3 of them Controller UI Control box and the Table, Gantry combo. We have a choice on fixturing methods, we have a choice on Spindle or Router, we can decide on our CAD CAM software and our cutters, which are all items we buy in addition to our ShopBot tool. which leads me to believe we would also have a choice in our Control Box and UI something that has not been available to us before is now readily available. Hooray.


Now on with it, Kerr geeesh!would you just spit it out all ready....

Not one too sit back and keep my trap shut, I thought I would give Alan at CustomCNC a call and see for myself what all of the commotion is about. Right from the word go folks he is one of us, a real CNC fellow who, as I was speaking to him had his wife running both of his ShopBot's in the background humming away ( OK I lied he is not like us, as many of us wish our wives were running our machines, damn it Alan tell us your secret).

I vollied several questions at him regarding the Mach3 UI and why he chose his what seemed to me at the time antiquated proxy switches, and of course the $50,000.oo question what feeds and speeds could I really accomplish with his offered set up, paired to my current PRT.

He answered each question knowledgably, and even when I offered some other suggestions he said hey that is a good idea, we should do that.

I have not seen his (in my best Homer simpson voice) "Magic Box" but after well over an hour on the phone with him, I will be giving it a whirl in the hopes that I can increase my shopbot from a 7.4V cordless drill, which still works but may take longer to a new 32V model that will run quiter and longer before charges, give me more speed and nicer output.


My only suggestion at this point to either Dirk or Alan is also to offer recomendations as to what should be done to an existing users PR or PRT table and gantry to ensure it is stiff enough to accomodate these new and improved feed and Jog rates. I find this info is lacking greatly from both parties at this time. This maybe an opportunity for another ShopBotter to create an additional product to offer this community.
Cheers, and if you're still reading this, man your life is boring. LOL
Dale

[jhicks]

Glad to see you back in action Dale. You always add new insight to the mix.

[joe]

I've had the plasure of worked with Dale on a couple of projects and glad he has made it back.

Welcome my friend.

[bleeth]

I didn't really think, that when I started this thread, the gist of much of the discussion would be Ascension vs Agek. I have nothing but respect for both developers and their systems and was hoping (I guess naively) that this thread would live as a stand-alone discussion of the merits and challenges in Dirk's developments and comparisons and contrasts to other's systems would be made elsewhere. Anyway, the resulting discussions are what free speech is about and since we are in a free society, it is what it is. In the interim, I have recently received an e-mail from a fellow shop-botter asking me if I had "before and after" type comparison photos of cuts to see the chatter differences. I answered him and then realized that my answer may be of interest to all of you following this discussion and so here it is:

I have not taken any pics of that as I am simply a consumer and not an agent. I can tell you that virtually all chatter I can attribute to the stepping difference has been eliminated. In a test file I ran of horizontal and verticle "race track" ovals, 10" D circles, and 10" stars, using a 2-d machining strategy with no ramped entries or lead-ins that I ran at 2ips with a 1/2" dull compression bit in 3/4" virola at a depth of .65 (leaving a skin for the vacuum hold down) I got smooth results except in one quadrant of the circles. That section I was easily able to attribute to the strain put on the stock gantry rails and car construction inherent in the PRT. It was also immediately clear, that from the moment we cranked up the new Agek control box/Alpha software setup, that 100% of the "gator growl" inherent in the PRT was gone. It simply runs a hell of a lot smoother like a cnc should. As I have stated publicly previously, to properly upgrade the PRT to take full advantage of the move and jog speeds possible under either system, one has to stiffen the gantry and car, or replace them.

I believe that the direct comparisons between what Custom CNC has done in two years against what Dirk has not developed as "professional marketing" appearance are irrelevant. Whatever one wishes to attribute to either entity as motives, they simply have different goals and a different start date of development.

I have stayed out of that part of the forum discussions because I feel that the importance being put on those aspects come from the wrong place. I have given Dirk that same advice. His sincerity and dedication in developing a Gecko driven system using Alpha SB software is as much an intellectual challenge for him as the profit motive, (IMHO) and since I didn't feel like or have the time to learn Mach software and g-code, which I am familiar with, as well as I know SBC already, I went with Dirk as a Beta user.

In today's technologically rapid developing world, three years is a long time. That is how old the replacement of the PRT as SB's best with the Alpha is. I would hardly expect my original PRT to perform like a new value priced CNC would, just as I would not expect the top of the line PC I bought 3 years ago for $2000 to do the same thing I would pay $2000 (plus inflation) for a top of the line PC today.

Your own needs and interests will lead you to make the right decision for you.

Regards;

Dave

[bleeth]

I have finally gotten the high speed serial card installed and working on my computer(delay due to my daily workload lately) and so was able to test rapid move on a jog test program I wrote in which I sent the xy scrambling all over the board in both diaganal, straight x, straight y and z moves. After around 10 minutes of running with the SB3 jog speed set at 16ips it suddenly lost steps in the x. I reset speed to 12, homed, and set off again. After quite a while there was no loss in steps and as far as I am concerned, that completes the test. From an original safe operating jog of around 3ips under my original PRT board and serial port, I have now quadrupled my normal jog speed with the Agek board and a Quatek high speed serial card. Cutting resolution at 1.7 through virola ply in two passes was sweet. I'll probably start cutting in one pass, leaving a skin with a fresh 1/2" down cutter as normal running parameters until I stiffen the gantry and car.

Dave

[srwtlc]

Dave,

When I get set up this next week, I'll take mine out for a jog and see what my results are. Would you care to share your jog test file for comparison sake?

Scott

[williamim]

I upgraded from the PRT to the ALPHA and I have upgraded again to the Ascension 1000 this upgrade was done for three reasons
1.

[jhicks]

William, Great justification logic that makes perfect sense and sounds all too familiar to our situation. Started up the ascension today but have a ways to go to fully understand and relate to the software. I think its a quick and intuitive package to learn with some cool features. All I can say is with minimal support and basic start up instructions, I couldn't wait to see it run.
Unbelieveablly smooth and quiet movement at 3 IPS on a PRT120. Not sure how it works, don't care how its accomplished, or what the magicians did. I like it and can't wait to go to the shop tomorrow to put it through more of its paces. Its like cutting leather with a butter knife vs butter with a razor.
But that's after only an hour or so of getting involved on a Saturday Am with the anxious anticipation of opening a gift from santa. We'll see how it feels after we run it though the paces a bit. Initial impressions are very positive!

[williamim]

Jerry it's great I know what you mean. I enjoy running the bot with the Ascension I can now start a file and go and do somrthing else in the shop and not worry about destroying a sheet of plywood. I am still impressed at the finished cut I am now getting. I find myself looking for different files to cut just to see the outcome. Just wait until you cut some 3d files I am sure it will put a smile on your face.

[harold_weber]

Dirk Hazeleger visited my shop and installed his control box on my 120 by 60 ShopBot. With the stock 3.6:1 geared steppers, we were able to jog my machine at a set speed 18 inches per second. Keep in mind that my machine has two Z-axes - one with a 30-pound spindle and one with a 20-pound spindle. I've built an increased length gantry to fit both spindles between the Y-rails. I'm also running 2 Y-motors plus stiffer (and heavier) Y-rail supports used on the Alpha machine. So there is quite a bit more gantry mass to accelerate and decelerate.

We were able to cut 18mm (3/4 inch) Baltic birch in 1 pass at 8 inches per second with Dirk's box and the stock 3.6:1 geared PRT stepper motors. I think Dirk was very surprised that we were able to cut full depth at that fast of a move speed, but keep in mind this cut was done with a 5.5 HP Perske spindle. We did not try to cut at even higher move speeds. In spite of the higher chip load, AGEK cut quality was better than with the ShopBot control box cutting at 3 inches per second.

402\

We also cut some circular test parts. After looking at all the test results, I decided I wanted to sacrifice the much higher jog speed to get additional smoothness of cut. The 3.6:1 geared steppers were replaced with 7.2:1 geared steppers.

With the 7.2 geared steppers, and the PRT control box, the speeds were limited to around 2.25 inches per second. To get increased speed, the combination of 7.2:1 geared steppers and the AGEK control box was tested. We cut a rectangle in one pass from 3/4 inch plywood at 8 inches per second with no missed steps.

Photos of two other test cuts were taken. A word on the photos is needed. Notice that for all the photos, the parts were held next to one another so EXACTLY the same lighting and camera settings were used to show the differences in cut quality. The primary lighting was located near the horizon and adjusted to MAXIMIZE the appearance of the surface roughness. The parts are stacked in order of increasing smoothness of cut as you move up through the stack of 4 parts. An impartial test person used her fingertips to judge the smoothness of the cuts.

For the test cuts in wood, 8-inch circles were cut from 3/4 inch thick soft maple on a vacuum fixture, and the final pass removed 0.050 inch over the full depth of the parts. The cutter was an Onsrud 60-121 (3/8 inch single flute mortise compression spiral bit).
403\

For the test cuts in 1/4 inch polycarbonate, 5 inch circles were cut with the part screwed to a spoil board, and the final pass removed 0.050 inch over the full depth of the parts. The cutter was an Onsrud 64-024 (1/4 inch downward spiral single flute Super O bit).
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The additional speed and smoothness of cut obtained with the AGEK box and the 7.2:1 geared steppers will allow me to take on work that I previously was unable to do. Your needs and mileage with your machine may vary................

[Brady Watson]

Harold,
How new are your pinions?

-B

[gerald_d]

Harold, those marks are very uneven/irregular. Reckon some mechanical maintenance would get you a smoother result.

Just wondering, if we are heading towards 10:1 ratios, we could be dumping steppers and going for servos?¿?

[harold_weber]

Hey Brady & Gerald, thanks for the comments. I welcome any thoughts that will improve on cut smoothness.

Brady, sorry I forgot to mention the pinions. I replaced the pinion gears when I switched to the 7.2:1 gearbox steppers. Here is a photo comparing the two. Its hard to see the differences because the tips of the teeth have slightly different chamfering (this from the manufacturer -Browning). The old pinion teeth were shiny (all machining marks were gone. You can see the teeth are not nearly as worn as the photo Gerald once shared.

Gerald, what mechanical maintenance will help improve smoothness of cut? Before running these tests, I pulled the motors away from the rack, cleaned the dirty grease from the rack and pinions, and re-greased. Ran the gantry and car up and down the rails to check for looseness or binding, and found none. Re-tightened the motor pivot bolts, and re-tensioned the springs holding the pinions to the racks. Because of the weight of my Y-car, I'm not using the Z-holddown rollers.

Any suggestions are welcome, but keep in mind what I said in the text of my earlier message: I did everything I could with the lighting and camera angle to make the cut roughness look as noticable as possible.
405

[harold_weber]

Hey Gerald,

I got to thinking about your comment that the machining marks are "very uneven/irregular". We actually made two copies of the cut circles, and Dirk took one copy. While I did not take photos of two copies cut with the same hardware laying next to another, I did line them up and all the tooling marks repeated exactly from one piece to the other. So the marks are regular in the sense that they do repeat from one part to the next. I don't know if this is what you meant or not.

[beacon14]

I saw an improvement in smoothness when I filed the bearing surfaces of my rails nice and smooth. This could partly explain the repeatability of the marks.

[harold_weber]

Thanks David,

I can check your suggestion by cutting the same part attached to two different x-y locations on the table.

[robert_cheal]

Can anyone explain the difference between the AGEK box and ShopBots new offering: (#15304) PRT 4g Control Board (w/4 Geckodrives)

Thanks,Robert

[Brady Watson]

Robert,
They are very similar and offer similar performance. It's just a matter of choosing who you want to give your money to. Both 'people' are highly reputable & put out a solution that works. For the brazen few who want to try monkeying with an Alpha board and Geckos themselves, there is quite a bit more to it than meets the eye. I got quite a bit of help from my friends at ShopBot to make mine work & I know that Dirk has also worked very hard with his system. The 4G PRT board/solution came together as a result of a few of us 'monkeys' trying to get it to work. (I personally take very little credit for any of this stuff!)

I have been running my own version here on my old PRT in "R&D" mode. This is the same rig that I ran Mach3 on...I like the Alpha/Gecko combo better because A) I know the SB language pretty well and B) I find that ramping is better and more sophisticated in SB3. Mach's 'constant contouring' is nothing more than turning ramping off. Having tried both systems, I found the ShopBot system to be a lot more intuitive and easier to use from beginner to advanced user. Mach has too many bells and whistles and was hard for me to get going with it. I think it's 'cute' that someone is developing an interface that uses ShopBot 2 letter commands on the front end of Mach3..If it's so easy to use, then why would anyone need this?...Anyway...I digress...On with the performance...

Speeds? At the moment, I am getting a solid 13 IPS and that is because I am choking on communication speed (serial communication...probably my older CPU doesn't help either). Other than that, I am really loving the setup. In terms of speed on an old PRT, this is nothing short of spectacular! Let's keep in mind that while your resolution will increase 2.5X with the Geckos, the number of pulses that get sent out to the controller also increases. So a stock PRT's unit values are roughly 733.xxx and a Gecko setup is 2.5X that or about 1833.xxx. This is where the smooooooothness comes in! I have another CNC that this particular control will go on (non-SB) and I am going to just buy a new PRT 4G setup from ShopBot that will replace this cobbled together setup and go on the PRT.

The 4G (4th Generation) is a combination of Alpha electronics and PLUG-IN(!) connectors for Gecko stepper drivers. It really is a sweet setup that was well thought out. I believe that there is a pic of it from the OH camp. I'm sure there will be more on it from ShopBot at some point in the near future announcing specifics, so I'll leave it at that for now.

Bottom line...It works!!!

-B

[robert_cheal]

Brady,
Thank you for the response I am sure others will be interested as well and the cost seems very reasonable. I am curious in Harold's post above where they changed out the 3:6:1 geared stepper with 7:2:1 steppers for increased resolution. On my PTR each motor has among other things a "7.2" on them I have not had time to look through my original documentation to see what I have. And being a electronically challeged fellow I find my self wondering about more than I presently understand. But I am excited about the possiblity of an upgrade.

Thanks again,
Robert

[gerald_d]

Harold, sorry I went to bed and dropped out of the thread for a while. The bigger marks on those cuts are irregular (at odd intervals), and they may even be caused by tiny dirt stuck on some v-roller somewhere. Folk reading this read for the purposes of comparing controllers should be ignoring the bigger marks and looking at the regular (evenly spaced) smaller marks instead.

[Brady Watson]

Robert,
The 'upgrade' is about as painless as it gets.

Your motors most likely if you ordered a hi-res Z-axis, only the Z will be 7.2:1 ~ the X & Y motors should be 3.6:1. There are a number of factors that affect smoothness and many of them boil down to machine maintenence, well thought out toolpaths and a true running router or spindle with the right bit chucked in it. A bit of fine-tuning for the type of work that you do via the VR command, makes a big difference. I change ramps depending on what I am cutting. One setting for 2D, one for small 3D, one for large 3D, etc.

Pinions have a large influence over cutting smoothness and what I have found in my travels is that most people neglect them and fail to realize when it is time to change them. What happens many times is people start off with a new PRT or Alpha and enjoy clean cuts in most materials. As time goes on, the pinions wear and their skills and eye for detail gets sharper...then they see that the tool doesn't cut so cleanly afterall...99% of the time because the pinions are worn and they rock a little in their mesh with the rack as a big gyroscope (router) pulls the tool in every which direction and the steppers try to hold it there. No problem with the steppers...there's slop in the pinions.

7.2:1 do afford some increased resolution at the expense of speed. Harold no doubt has a good serial communication card installed in his tool that gives him a max speed of 8 IPS. This would translate to roughly 16 IPS on a 3.6:1 tool. For all of us that started out with a PRT many years ago, this is a big, bright wonderful day. All we wanted was an extra 1 or 2 IPS in cutting speed...Those experimenting with 7.2:1 motors may find some additional smoothness + a speed gain by increasing the pinion size.

-B

[harold_weber]

Gerald, thanks for the thought on possible dirt packed into the roller V-grooves. I had not thought of that and will check on it today.

Robert, one difference between the AGEK board and the ShopBot Gecko board is that AGEK is built/wired to take up to 6 Gecko drives. To get to 6 Geckos if you go with the ShopBot/Gecko system, I believe you will need to buy 2 of their boards.

[gerald_d]

Why would we want so many drives? The z-axis is not that fussy and the current Allegros can be retained for that. And then the SB software doesn't square the gantry, so we might even be able to use one 7-amp drive to drive both x motors in parallel. Using 2 drives sounds a lot better than 6!


In fact, why get hung up only on the gecko brand? There are a couple of other brands of tenth-microstep drives out there that can handle the smallish SB motors.

[Brady Watson]

http://www.shopbottools.com/PRT_4g_Upgrade.htm

[richards]

Here is a photo of some MDF plaques that I cut last week (except the bottom plaque that was cut last year). The lack of 'chatter' on all but the bottom plaque can be directly attributed to a 3:1 belt drive that I installed on my Alpha a few weeks ago. Nothing else changed.

Spindle speed was 14,000 RPM. Feed speed was 8-ips (two passes, one climb cut to -0.40 and one conventional to -0.535 with 0.030 skin left to hold vacuum. I used a 3/8-inch 2-flute downcut spiral carbide cutter.

The top plaques are from a batch of 64 plaques that were cut from the same piece of MDF. Other than chamfering the top, each piece looks exactly like it did when it was cut on the Alpha. The bottom plaque shows average 'chatter' that I always got before installing the belt-drive gearbox.

The light was angled to show as much of the 'chatter' as possible. The top five plaques are 'chatter' free. The bottom plaque shows the 'chatter' that I had from day-one until gearing down the motors 3:1.


406

My cuts in polycarbonate and baltic birch are very similar to Harold's 7.2:1 photos. I haven't cut soft maple, so I can't make a direct comparison.

[gerald_d]

One can't help deducing that this ShopBot PRT4g comes as a reaction to Alan's Ascension and Dirk's Agek. I know Dirk put a lot of work into preserving the use of SB software with Geckos, now it would appear that they are competing? Will this PRT4g also make an appearance at Gary's Kansas camp? Performance-wise, it sounds as if the PRT4g and the Alpha will be about on par - what then is the place of the expensive Alpha? Components are recovered from traded in PRT boards - for new PRT's? Intriguing....

[Brady Watson]

The 4G is not on par with the Alpha. It's still slower, has less torque and no positional feedback. You still can't jog over a max of 16-18 IPS if all is dialed in. Fast jogging is appealing to some who do certain type of work that would benefit from it, mainly those who need an industrial grade tool. The G4 is a tremendous improvement over the original PRT...but not quite an Alpha. You really have to see one of these things in action to appreciate the sheer simplicity of the setup and performance gain it gives you by just swapping out a few wires! A 305 oz motor driven @ 48v is still less powerful than a 560 oz motor driven @ 160v. Gearing would give some resolution advantages at the cost of speed...a 5HP motor still makes 5HP regardless of what gearbox you put behind it. The Alpha is an industrial grade solution, and the PRT is an introductory/standard CNC from what I read on the SB site. While it won't do what an Alpha will, I imagine that most of the PRT guys won't really care to split hairs after they see it run. It's like having a new tool again!

I sincerely doubt that ShopBot would even consider selling used components on a new CNC in their wildest pipe dreams...I would guess that it would give customers an option to afford good used Allegro drivers than new ones if they were getting their original PRT boards repaired. I can only guess at this, since ShopBot has been pretty good about keeping CNC affordable & I don't know for sure where the old boards/components will go. Think of your board as your ShopBot 'dongle'...you have to pay for the license to use the SB stuff.

-B

[robert_cheal]

If I understand what I am reading on all of my PRT stepper motors "PK296A1A-SG7.2" I would think that all motors have a 7.2:1 gear ratio.
Is there something that I am missing or is this correct? Just curious when seems like 3.6:1 was standard for X and Y motors.

Thanks, Robert

[Brady Watson]

You must have a 'custom' tool, which may have been special ordered from day 1 with 7.2:1 gearing all around.

-B

[robert_cheal]

Brady,
I took delivery of my PRT in early 2001 and I ordered the basic PRT 48x96. It seems like my paper work mentioned something about the gearing for more torque and less speed. I'm still looking for the documents. Thanks for the clarification.

Robert

[richards]

Granted that a PRT with stock motors, which are similar to the PH296A1A-SG3.6 from Oriental Motors, and an Alpha running Oriental Motors AS911AA steppers with Alpha stepper driver are two totally different animals. According to Oriental's website, the PK296 with SG3.6 gearbox has a top torque output of 300 oz*in, which is the same as the PK296 without a gearbox. So the gearbox is the limiting piece in the race for higher torque. The SG gearbox's components are limited to 300 oz*in. The Alpha stepper has twice as much torque, without a gearbox, and many times the speed of the PRT. Those are basic specs for machines direct from Shopbot - to the best of my knowledge.

However, my Alpha, in it's factory configuration has one very serious flaw, it produces cuts with way too much 'chatter'. It is fast, both in feed speeds and jog speeds, but the cuts produced could barely be called adequate for the type of work that I do - basic cabinets mostly. On the other hand, the PRT gave cuts that had little 'chatter' (according to several users that I've talked to) but were just too slow at 2-3 ips instead of 6-10 ips on the Alpha.

Dirk's AGEK fixes the speed problem, but, if the original motors are used, I believe that torque will still be limited by the gearbox. By adding Dirk's AGEK and new motors (PK299-02AA) for instance and upping the power feeding the Gecko stepper drivers to 70VDC or so, you'll have Alpha performance on your PRT. (You'll notice that I haven't considered positional feedback to be a plus. Until something is done so that all axes are tightly controlled by a master feedback loop, so that all axes slow down when any axis slows down, in my opinion, the positional feedback, as now implemented, gives ruined parts when any axis drops into 'feedback' mode, especially if one of the X-axis motors goes into 'feedback' mode. Email me if you have questions about what happens when a single motor slows and starts acting like a pivot point.)

Adding a belt-driven gearbox turned my Alpha into the machine that I thought I was buying in 2004. It can now do anything that I expect it to do. I would assume that a PRT using Dirk's AGEK and new motors with a belt-driven gearbox would perform just like my Alpha but give twice the resolution per shaft rotation of the stepper motor (Gecko drivers put out 2,000 steps per shaft revolution while the Alpha puts out 1,000 steps per shaft revolution as it is factory configured.)

One thing to keep in mind is that CURRENT determines a stepper motor's torque and VOLTAGE determines its speed. If you wire the PK299-02AA motor using 1/2 coil connections instead of using the full coil, you will get excellent torque and excellent speed with a 70 VDC power supply that is functionally identical to the Alpha's AS911AA motor.

My personal recomendation if you're an Alpha owner is to build or buy a belt-driven gear box and enjoy 'chatter' free operation. If you're a PRT owner, buy Dirk's AGEK and replace your steppers with PK299-02AA motors and then build or buy a belt-driven gear box so that you'll have Alpha performance at 3X the torque. If you're leaning towards the Ascension box, go to the Ascension web site and read Jerry Hick's excellent report on the learning curve that he faced when he went from Shopbot code to G-code. Jerry is a great guy who calls an ace an ace. His personal experience of the difficulty in going from Shopbot code to G-code should be read and read and read again by anyone contemplating making the change.

[Brady Watson]

Mike,
Does that mean that the PH296A1A-SG3.6 is really a 100 oz stepper with a 3.6:1 ratio gearbox that puts out @ 300 oz @ the shaft? This always boggled me when trying to figure out the PRTs real motor power.

I've got my box running on a full 80v (with safety overvoltage dump with no problems with the Geckos overheating or clipping) and I get about 50 lbs of force @ 8 IPS on the PRT using the "fish scale method". The 7.2:1 Alpha I have (can't compare a 1:1) will pull 150-160 lbs (!!!) of force before starting to stall/go into Alpha mode @ 8 IPS (it will actually do this up to 10.5 or 11 IPS). Not to confuse the Alpha electronics with the Gecko/PRT stuff as the Alpha electronics are very different, giving you greater speed advantages because of the Alpha motor drivers. It does things that a Gecko simply cannot do (and it should for the price differential). I can cut @ pretty much full force up to 12 & Jog @ 30 IPS. Not going to do that with the PRT while maintaining low speed performance and resolution.

The PRT will now cut 3D @ 8,8 just like the Alpha does with some ramping tweaks. I'd love to post a pic of 2D edge cuts, but I am in the middle of a large 3D panel scan at the moment that will take several days to complete (the PRT is the resident digitizer...a 4X4 will soon take it's place and the PRT will be 'allowed' back into production) It would be interesting to me personally to see how the PRT with Geckos & 3.6:1 compares to my 7.2:1 Alpha in cut quality. More on that when I get the time...

In terms of 'Alpha mode' and positional feedback, I never had it go out of line and unsync the X motors. This could be due to the fact that it has 2X the torque of a standard Alpha. I like the idea of it for nothing more than 3D raster cuts that used to stall the PRT at the ends of rastering...and ruined parts. That alone is worth it to me. I too wondered why all axes were not 'indexed' with one another, and the answer really came down to cost. Would you want to spend another $5-7k on an indexed setup (guessing at prices here) on top of the price of an Alpha? Do you REALLY need that capability? So far for me, the answer has been a resounding 'no' to both. I think you get that indexing capability on $150k tools...One must ask, when is enough enough?

As far as the PRT machine goes, it definately has more usable torque. This is most likely due to the fact that the increased voltage pushes the torque curve up a bit higher and the Geckos push more current thru them than the Allegros will allow. I've got mine set at 2A, which makes the PRT motors a little warm, but not hot.

-B

[richards]

Brady,
I don't think it's a question of motor torque vs geared torque. All of the PK296 motors show 300 oz*in torque on their performance charts. The SG geared motors all have a flat line seqment that drops off into a torque curve, showing that there is something about the motor/gearbox combo that limits the torque rating of the motor/gearbox. In an attempt to find out why that was, last July, while I was sitting in my truck in L.A. in a Best Western parking lot, trying to decide whether to take a few hours and drive over to Oriental Motor and pick up four PK296A2B-SG3.6 motors or whether to just drive back to Salt Lake, I called Oriental Motor to verify the torque rating of the Pk296A2B-SG3.6 motor, because the torque rating of the geared motor was NOT 3.6 times the torque rating of the ungeared PK296-02AA motor. The tech rep told me that components in the gear box were rated to 20 lb*in (320 oz*in), and because of that, the 3.6 torque multiplier that I expected because of the mechanical gear box, did not apply to the PH296A2B-SG3.6 motor. That was a big disappointment, causing me to return to Salt Lake City without purchasing the motors. Since then, I have purchased four PK296A2B-SG3.6 motors and have tested them extensively on my Gecko test bench. Although I haven't tested them to destruction, I have tested them beyond their designed torque rating without failure; however, I trust Oriental Motor enough to believe that continual use of the PK296A2B-SG3.6 above 20 lb*in torque will eventually lead to gearbox failure. When that failure will occur is anyone's guess, but with my luck, it would be in the middle of an important job. That being said, I fully realise that the Alpha 7.2:1 geared motor uses a totally different gear box than the PK296 series motors. The gearbox for the Alpha seems to be rated at the torque multiplier expected when using a 600 oz*in motor mechanically geared down 7.2:1. That's great, but it costs almost 10X what a $261 PK296A2B-SG7.2 motor costs.

Using the same 'fish scale' method of measuring torque, I've found that a PK299-02AA motor, being driven with a Gecko G202 drive at 70 VDC and drawing 3amps of current has virtually the same torque characteristics of the AS911AA motor being driven with the Alpha stepper driver. Of course, I haven't tested all speeds and varying ramps settings, but the tests basically showed me that an inexpensive motor ($206) with Gecko driver ($150) and proper power supply ($200 for four motors/drivers) competed very well with a $1,100 Alpha unit.

Unfortunately, my experience with the Alpha 'feedback' has not been very good. In everycase, the 'feedback' allowed the cut to continue, but with obvious 'divots' along the cut that ruined the part. Since adding the belted-gearboxes to my Alpha, I haven't had any of the motors go into 'feedback' mode, so it has ceased to be a problem. I agree with you that expecting full feedback on a $15,000 machine is expecting the impossible; however, I think that advertising that a machine has feedback, when that feedback leads to ruined cuts borders on the unethical. Perhaps it would be better if someone inserted an asterisk in the sales literature explaining that the feedback is single axis only without communication between the three axes of the machine and that ruined parts could/would result if the 'feedback' feature actually goes active. At least that would make me blame only myself when I have to toss out another $80 sheet of plywood.

Also, I agree with you that the Geckos can push enough current to accommodate the stepper motors so that they're not starving for current. The motors running from a Gecko driver and at higher voltages do run a little hotter than motors running from lesser drivers. I don't use Allegros, but I have a number of Oriental Motors CSK drivers that run at 24/36 volts. On some of the motors that I've tested, I've run the Geckos at 7-amps. When drawing that much current the Geckos need a healthy heat sink. (I use an aluminum bar, three inches wide, fifteen inches long and one inch thick to cool four Gecko drivers. With that heat sink in place, everything runs cool.) However, I have gotten the motors really hot by running more than the recommended 25X voltage through them. Normally, I've found that 10X to 15X voltage gives perfectly adequate speed without creating too much heat.

Bottom line, I think that anyone wanting to upgrade their PRT machine should expect to pay about $2,500 for Dirk's box and at least three new PK299-02AA motors (with the Z-axis left with factory motor). That's not too much to pay, in my opinion, to get Alpha performance from a PRT machine. On the other hand, I also think that adding a gearbox (belt-driven in my case) to a stock Alpha, at a cost of about $500 is the least expensive way to get rid of the Alpha's 'chatter' problem.

[Brady Watson]

Mike,
Good discussion. As far as the gearing/torque ratings on the gearboxes go, I would think that the stepper would break it's electrical/magnetic lock before you would hurt the gearbox. I don't think that Oriental would put a motor behind the box that had enough torque to kill it. In testing my Gecko setup I told it to jog @ 20 IPS and the motor started moving the gantry and stopped (stalled)...It sounded like a missed 2-3 shift where the syncro engaged and the gear was trying to...not quite spoons in a blender but...no apparent harm was done to the motors or gearboxes.

As far as the feedback thing goes, I feel your pain...but when you encounter lost steps & the tell tale signs of correction, the tool is telling you that you are pushing it too hard, too fast or both. Slowing things down a little may prevent it from ever going into Alpha mode. I don't think that I would go so far as to say that ShopBot has falsely advertised the Alpha. It does what is says it does...and for the money, there are very few if any manufacturers of comparable tool quality that offer ANY type of feedback system at all. I'll take something over nothing in this case. Been there with the PRT of old and can no longer afford the luxury of missed steps or long cutting times...Although the 4G setup now offered by ShopBot really raises the bar for the PRT. I think of it as a VW Beetle (like my '67 I had in HS) in which they added a Porsche 911 drivetrain to...

On a side note, I never understood why people insisted on cutting 3/4" sheets at full depth passes. It doesn't take that much longer to cut it in 2 and you know you are going to get a lot less tool deflection. If this is production...OK...but most shops I have visited are perfectly content doing it in 2 passes @ 10-12 IPS with no Alpha mode jitters. Those shops that NEED to cut full depth at those speeds require some ramp tuning. If you are still using the default ramping and pushing the tool to it's limits, you must dial in the ramping. EG- Change your slow corner speed to 35 to cushion the starts and stops. 65 WILL knock the tool out at those speeds. (Mike this is not necessarily directed at you...it may be of benefit to those readers lurking behind the scenes)

Resolution via mechanical means really does help things out as far as smoothness & torque. I'm glad that you did the testing and gave all of us feedback on your success ~ Thanks! I guess the question for those (and me with 1:1 standard steppers going on the 4X4 tool) is how can we get a set of affordable gearboxes/belt-drives in our hot little hands? After messing with AL this past week, I think that the Alpha can mill out the bearing lands and the mounting plate...but others may not feel comfortable doing that themselves...I would be willing to collaborate on developing some kind of kit with those who are actually willing to work on the project with both hands out of their pockets.

It's nice to have the room to have these discussions...appologies to the non-techies who have gotten lost in all of this! Keep reading and playing with your ShopBot...You'll get it!

-B

[robert_cheal]

It feels a bit like watching a votex of heavy traffic spinning into round-about in Cairo,Egypt then a little old man with a donkey cart plunges in to the middle of it. I still wonder if he made it.

Robert

[Brady Watson]

Hey Robert,
No need to sit back and be discontent with your current knowledge of this stuff. There are no stupid questions...So instead of being 'lost', ask questions! Nobody knows everything...including me...so ask away!
What is confusing to you? What do you want to learn/know?

-B

[richards]

Brady,
I agree, we're getting a little beyond the fluff level here. Hopefully, those that only want a machine to work and don't really care what's inside won't be offended. Personally, I'm a naturally curious person who enjoys finding out how things work and why they have limitations.

Back to the SG gearbox (Spur Gear) gearbox that Oriental Motor uses on its PK296 motors, it uses spur gears without documentation on the size of the gears or of the material that those gears are made from. Spur gears are often made of phenolic, Delrin, brass, as well as other materials with steel not necessarily being the material used. The size of the indiviual gears, particularly the size of the individual teeth could be the factor limiting the advertised torque of the SG gearbox. On the other hand, the Planetary Gears, Harmonic Gears, and Tapered Gears all seem to offer higher torque - at significantly higher prices. Unfortunately, the PK296 motor is only offered with the Spur Gear option. Granted, external gearboxes, of every type, are available from other sources that would allow the PK296 motor to generate 3.6X, 7.2X or higher torque, depending on the gear ratio choosen. My guess, and it is only a guess, is that some of the teeth in the SG gearbox are small enough that continued high-torque usage would lead to premature failure. (If you're like me, even though the Shopbot controller card can jog a geared motor at 30-ips, I've cut my jog speed down to 12-ips. In the past, when I got careless and bumped into something at jog speed, the Alpha motor(s) would stall out and the move would be aborted - without causing damage to the machine. With a 3:1 drive, the motors don't stall out and damage to the weakest link can occur. So far, I've only snapped a bit, but that kind of force can't be good for the spindle's bearings.)

Your comments on cutting too fast for existing conditions causing the Alpha motors to enter feed-back mode are certainly true. Normally, the way that I set up for a production run is to select a chipload and then use various combinations of move speed/spindle RPM until the VFD's amp reading for my 3hp spindle stays between 6.5 and 7 amps. That process works very well for particle board, MDF, and Baltic-birch plywood, but normal cabinet grade plywood (the above mentioned $80 per sheet stuff), seems to be less consistant in manufacture than the other sheet goods. I don't know whether it's knots in the inner layers, variations in gluing or just bad luck, but that particular material gave me the largest number of feedback problems. In a system using the $400 Gecko G100 pulse generator and encoders on each motor, feedback/slowdown problems will be syncronized between as many as six motors. (Of course, the G100 is still being readied for market. Most features work, but total syncronization between all motors still hasn't been released.)

As far as building an affordable gearbox for non-geared motors, I'm still playing around with various designs. Just today, I finally got my vertical mill properly setup - but it's still a manual mill. Without CNC controls, a vertical mill is limited to basic cuts, unless three operators can learn to crank handles in tune to the beat of a conductor. Delrin or polycarbonate, which can be cut fairly fast on a Shopbot, probably work just as good as aluminum in a belt-drive gear box, given the fact that a one-bolt-attaching system will probably allow flex regardless of the material being used - but aluminum looks so much better than plastic and aluminum is a good heat-sink for the additional heat produced by running steppers at 3X the speed of a non-geared motor. I think the word affordable is the operative word. Cutting metal takes time, and, unless it's a labor of love, there are costs that have to be paid for by someone. A belt-drive gearbox has the advantage of zero-backlash, when compared to an SG type gearbox, and, it seems that the natural elasticity of the belt dampens the drive enough that the minor 'chatter' patterns visible in some of the SG driven photos just don't happen with a belt-drive, but there could easily be other factors at play. However, how many Shopbotters would pay as much per axis for a belt-driven gearbox as they would have to spend per axis for a motor with an SG gearbox already attached? (I did the conservative thing when I started designing the belt-drive. I ordered four PK296A2B-SG3.6 motors as backup motors if the belt-drive didn't work. Fortunately my Alpha turned into a sweet-running CNC machine with the addition of the belt-driven gearbox. By the way, did I ever mention that cuts full of 'chatter', pre-belt-driven gearbox days, was really driving me nuts?)

There seems to be no perfect solution for everybody, but lots of people are working on additions and fixes to known problems - which makes the Shopbot community such a great place. Most of the claims being made for 'hot-rod' shopbots are backed up with testimonials, documentation and photos showing before and after pictures. And best of all, anyone with a calculator can run the numbers and then feel confident that the reports of the various systems are mathmatically sound.

[gabepari]

Recently, I had my Alpha miss steps during a cut and continue on it's merry way, ruining a nice sheet of pre-finished baltic birch. A small part broke free and got wedged between the cutter and the rest of the nested parts, after a brief groaning, the bot kept on cutting, but 1/4" off on the far x-axis motor. I don't think I skipped a tooth on the pinion, as I was standing right there when it happened and didn't notice any bounce of the gantry. No fault was ever detected. Turned the bot off and the gantry snapped back square when the motors de-energized.

I'm getting a small amount of the Alpha chatter, I've chased most of it down to cutter flex and general flex in the gantry, z-axis, v-rollers, and rails. Try putting a dial caliper on the gantry some time and start pushing on things, flexes like a wet noodle (well, a really stiff wet noodle
) One thing that would really help is to put all the rollers in double shear. Anyways, going off topic. Also, I'm going to jump on the "3:1 belt drive box" bandwagon real soon, got all the parts, just need some time.

Back to Geckos. I've got all the parts to build a second z-axis (small stepper belt driven ballscrew with dual linear rails, mainly aimed at moving a laminate router up and down to poke little holes in 1/2" baltic birch), and was wondering if a 212 will plug and play with the Alpha box? I've already got the 212, just haven't had the time to wire it up yet and give it a go.

Keep the discussion going, I like to troll


Gabe Pari
www.socalteardrops.com (http://www.socalteardrops.com)

[Brady Watson]

Gabe,
A 212 is plug & play...a 202 using an Alpha board is not. This is because the 212 is common (-) which is what the Alpha uses and the 202 common terminal is (+).

-B

[gerald_d]

Wonder if the ez-Router "beltbox" would be an economical/easy fit.....hmmmmm

[gerald_d]

This "conversion" debate is mostly focussing on resolution, cut quality and speed. These factors havn't bothered us as much as reliability. We havn't blown a Gecko-drive. Mach3 gives us something that works in Windows and millimeters. The parallel port interface is reliable. We can run G-Code which is more capable of 3D interpolation.

I wouldn't say that the brand names Mach and Gecko are the be_all and_end all of the generic components. Mach3 is definitely buggy for our application, but not to the extent that it causes us to scrap boards. The Gecko-drives have stiff competition and a totally new version is out soon - time will tell if the new version (the Vampire) is as reliable.

The CNC router environment is changing very rapidly. Nobody can rest on their laurels. IMHO, SB's latest development puts them back a few years - to catch up to the rest of the field. Let's hope that some real "advances" in technology are lurking in Durham. (G-Rex with proper inter-axis feedback? Servos?)

[dirk]

Gabe
One word of caution using the 212. The 212 is jumper selectable as to ground common. Using the 212 for your stated purpose should work fine, however if your using it to VCarve or any movements that require very short steps the multiplier portion of the drive will cause you to loose or gain Z position. This is very slight but will show up on large files of this type. On both The AGek and SB's board the signal is inverted and the 212 is no longer used.
Dirk

[mziegler]

Brady, thanks for the information on the pinions. I now think the slop in the pinions is what causing my poor cuts. That make sense, as time goes by the pinions are worn and so there is more slop in the machine. Now it be good time to change out pinions because I upgraded to the Agek box. Mark

[richards]

Gabe.
Dirk's word of caution should probably been printed in red. He found a serious undocumented flaw in the functionality of the Gecko pulse multiplier board that affects accuracy. The G212 should be turned into a G202 by removing the Gecko pulse multiplier board and inserting the proper opto-coupler into the 8-pin socket. (Sorry, but I'm not at the shop, so I can't check the part number.) I've dumbed down all of my G212 drivers to G202s and my G340 drivers to G320s by removing the pulse multiplier boards and inserting the opto-coupler chip.

You can design a signal inverter using a 7404 chip (be sure to use the full power versions of the 7404 and NOT the 74LS04). Of course any number of other 'inverter' chips could be substituted for a 7404. You could even use a single transistor to invert the signal. The Gecko drivers require 16ma to operate their internal opto-coupler properly. The LS series of chips can't drive that much current.

From an historical point of view, digital circuits have always been designed to be 'active low', which means that a LOW or zero voltage is ON and a HIGH or 5VDC voltage is OFF. That was the way things were designed because the chips that were most commonly used, until very recently, could SINK much more current than they could SOURCE. In the case of an opto-coupler circuit, one side of the internal L.E.D. was always connected to the VCC or 5VDC side of the circuit and the other side of the internal L.E.D. was connected to the controller chip through a resistor that limited the current to 10 to 15 milliamps. The L.E.D. was turned on - lit up - when the controller chip's voltage was LOW or zero volts. Somewhere along the way, designers started using chips that could either SINK or SOURCE current equally well, and the old 'standard' way of designing circuits no longer applied. The problem now is that some devices expect to be connected to a current SINK (the G202 driver, for instance) and other devices expect to be connected to a current SOURCE. The Alpha controller SOURCES current, making it necessary to add the inverter circuit.

If you're into designing circuits, you might want to lengthen the pulse generated by the Alpha controller card to a minimum width of 5usec (as required by a Gecko driver). The Alpha controller card generates a pulse width of about 2usec (which does NOT cause problems as far as I know). However, a 555 timer chip could both invert the pulse and lengthen to pulse at the same time for about the same cost and complexity as designing a 7404 circuit. The added advantage is that the 555 is designed to sink or source much more current than the G202 requires.

By the way, Gabe, you haven't posted your method of climb cutting and then conventional cutting (or I've missed the post). Since I visited you, I've been using your method on everything and have been getting perfect cuts without figuring tolerances and offsets like I did before you showed me the correct and easy way to cut.

[richards]

Gerald, the 'ez-router' uses a plastic gear as part of their drive chain - unless I misunderstood their correspondance. Their transmission unit is priced at $175 each. Also, they use a single plate which I thought wouldn't be rigid enough to properly support the drive shaft. My first belt-drive used a single plate design, but I rejected it when I noticed that it was too 'floppy'. Granted, I'm not a mechanical engineer and my designs tend to evolve after a period of trial and error, but my initial three designs led me to belive that 'stronger is better' and that two plates or, at the very least, widely separated bearing blocks, give much less flex than closely separated bearing blocks.

Your other post mentioned using servos instead of steppers. Anyone using Gecko drivers can swap out the G2xx drivers and install G3xx drivers to run brushed servos. An ID300x servo with encoder costs about $250. Other than requiring gearing to slow the servos down, they are basically a drop-in replacement for steppers - and, because of the encoders, they automatically have built in 'feedback' circuits that function much like the 'feedback' circuit of the Oriental Alpha motor. On my test bench, I constantly intermix steppers and servos. Steppers are easier to use only because I'm more familiar with them. Brushed servos are faster, stronger, quieter, but they do require a faster pulse train. If they're only geared down 3:1 to 7.2:1, they should be totally compatible with the pulse train generated by Shopbot's controller cards.

[kaaboom_99]

Okay guys, where are you getting the gearbox ratio data (on a stock PRT circ '99). All I can find is this info (off the stepper), "Vexta" "A6497-9412KTG"
"2 phase" "0.5°/step".
So what gearbox ratio do I have? With all this talk, I just had to check.

[Brady Watson]

Yes...the 212s... The 201, 202 and soon to be 203v drives are the only ones you want. The drives that use the pulse multiplier (not sure if the 340 has the condition...but it does have the multiplier board)...as Dirk pointed out, it throws out small movements and generates positional errors. Of course we ALL (the secret monkey tinkerer team) found this out AFTER we all bought 212s for $30-something more a piece. You can thank Ted and his hours of research for that little gem of information. This is a problem regardless of whether you run SB3 or Mach...I am totally suprised that the Mach guys running the 212s haven't picked up on this fact yet...guess they are lagging behind...LOL!

As far as going backwards in terms of CNC 'evolution', that's just a matter of opinion as the majority of us who run ShopBot tools feel just the opposite. We have just crossed over the threshold of having our cake and eating it to from a control flexibility standpoint. If anything, using the parallel port out of the PC is going backwards since it offers no safety disconnects (tool can run away) if it becomes unplugged or interrupted, and acts like a big antenna prone to electrical noise common in industrial settings (despite delusions of granduer, my/your little shop/garage is not an industrial setting full of electrical noise from heavy machinery). Serial & USB won't cause a tool to run away and are less prone to electrical noise. So for a tinkerer in his garage parallel may be a good solution, but it has no business on an industrial tool. If parallel was so great (it does have more communication speed) as an all around solution, ShopBot would be using it (they did acutally on their earlier tools and there is a reason why they no longer do!)

As far as the G100, it's a nice little setup and who knows, maybe one day SB will offer something that uses that technology. I know personally, it needs to become a bit more user friendly in it's implementation before I buy one. After the 212/201 positional error discovery, a full gamut of testing is in order for the G100 to make sure it is suitable for CNC control. (CNC applications are a very, very small part of Geckodrive's business) For now, the SB technology is working just fine considering the price at which it is offered in the marketplace. So much so that it is now cheaper to piece together a G4 setup to run on any CNC under 7A/motor than a comparable Mach3 setup. Now that is a real breakthrough! I doubt that the G100 is any better than the Alpha when the rubber meets the road (or where the bit meets the material) when all is said & done for 99% of ShopBot users. The need for indexing on all axes is very small. Even if you could theoretically have a really 'tight' machine that would run 25,25 IPS, could you really use it? Doubtful...then after the machine controller is equivalent to the 'ultimate' of the day, the spindle needs to be better, and the table needs to be better and it all needs to be better...At that point, just buy a Komo and make the payments. It will cost you more $ to make a Mustang into an F1 car than just buying the F1 to begin with. None of us NEED an F1 (boy it sure would be nice though!)...but I think we can all settle on a good handling affordable sports car that we can work on ourselves.

Perry,
Your motors are 3.6:1 standard PRT.

-B

[dirk]

You Have a 3.6 gear reducer
200 steps per revolution
divided by 360 degrees = 1.8
1.8 divided by a 3.6 reducer = .5 degrees per step.
Dirk

[kaaboom_99]

Thanks guys, I was just curious how the formula.

[richards]

Brady,
Hopefully you won't think that this is a personal attack on you or on anyone at Shopbot. I know how long development cycles can be and how much is at stake if customers decide to wait for future products instead of buying and getting use out of current products. When that happens both the company and the customer suffer. That is not my intent, but I've just bought a brand new soap box that needs to be broken in - so here goes.

If I may, I'd like to give a different opinion about the parallel port than the one that you gave. You basically stated that there is a danger of things running on their own if the port is disconnected. I find that a little hard to believe. The pulse stream to run the steppers is NOT generated by the parallel port. If the parallel port is disconnected, the pulse stream is also disconnected and all stepper activity stops. A properly connected parallel breakout board has a 'charge pump' that acts as a 'dead-man's switch' to disable the outputs on the parallel board if the pulse train to the charge pump stops i.e. if the parallel port is disconnected. All in all, it works very well.

You and I also have divergent opinions about the Gecko G100. Right now, out-of-the-box, it works perfectly with Mach3 software - with the exception of sycnronized feedback from the steppers - meaning that it generates step pulses many multiples of times faster than either the Shopbot controller running through a USP connector or standard Mach3 running through a parallel port. The only drawback to it is that to use it today, without writing your own software, you have to convert to Mach3 G-code. Mach3 and G-code are great, but, at the present time, I'm not willing to make that conversion. That day is approaching, but it hasn't yet arrived. BUT, I think it might be a huge mistake to ignore what the G100 can do TODAY. It has native ability to control six axis at one time (X/Y/Z plus 2nd Z plus indexer with one axis for future expansion). It can syncronize movement on all six axes at once although my imagination can't conceive of anything more complex than boring a circular helix, which only uses three axes. It can send a perfect pulse stream (without jitter) at 200,000+ pulses per second. The USB interface chokes on speeds MUCH lower than that and the top speed that Mach software can pulse the parallel interface is about 45,000 pps. It has many times the I/O - both analog as well as digital - as that found on the Shopbot controller or the standard breakout boards normally used with Mach3. It only costs $400 + $150 for the Mach software.

Now, don't misunderstand, I'm not promoting the G100 nor am I promoting Mach3 software. I use both extensively on the test bench simply because I, as a CNC router owner, must be ready and able to use every possible tool when my competition starts to offer services that require the G100. Pretending that the G100 is just a toy is, in my opinion, a good way to fall way behind the competition. Some people might think that G100 and Mach software are being co-developed. As far as I know, they're not. Art, who writes Mach software, and Mariss, who designed the G100, are good friends who communicate freely with each other and whoever else is interested in their products, but they each have their own teams. Shopbot could incorporate the G100 into its software just as 'easily' as the Mach people are incorporating it into their software. However, as those of us who have run the software race most of our lives already know, if you're not already developing for new technology, you're already too far behind to ever catch up.

To be very blunt, I think that anyone who can't or won't see what will happen when (not if) anyone can buy a $400 G100, connect stepper or servo drivers at $150 each, add quality stepper motors at $200 each or servo motors with encoders for $250 each, install a heavy duty power supply for $200 each, and then add whatever I/O is required for the cost of parts, is going to wonder what happened to their business. The software will be the only unique feature that clearly defines the differences between companies. Can anyone remember IMSAI, CROMEMCO, THINKER-TOYS, and the miriad of other good solid computer companies that died when they ignored the little upstart company called Apple? Does anyone wonder why Bill Gates has pre-announced his retirement from active duty at Microsoft? Could it be because entire countries have banned the use of Microsoft software in all government offices, preferring instead to trust a fellow from Finland named Linus Torvalds and the software that he created over the blustering Microsoft? Maybe I get a little too worked up when good people and good companies ignore change, but I've just seen too many companies collapse because they "didn't see it coming" (including the entire professional photo lab industry that no longer exists because of digital photography. Hundreds of companies that employed thousands of people and owned millions of dollars of equipment slipped into bankruptcy within a period of a few months when they ignored new trends.)

Personally, I think that open discussion on an open forum helps a company understand what their customers are expecting to be able to buy just as it helps customers openly debate products, both current and future. Spreading FUD (fear, uncertainty and doubt) doesn't work. Researching and embracing new concepts, while keeping both feet firmly planted in reality leads to vibrant, healthy companies that never fall behind their customers' expectations.

[Brady Watson]

Mike,
No offense taken at all...This is a discussion after all, and out of conversation comes a clearer picture and new perspectives.

We can agree to disagree about the parallel port and it's suitability on an industrial tool. While a charge pump would eliminate the run away tool condition, it does not address the electrical noise issue. I personally have run parallel on Mach in my shop with no problems like that, but electrical noise is pretty low in my shop. I hear ya on the communication speed of all described and agree 100%. Maybe a new communication protocol will crop up in the PC world that will be a happy medium between what is available to us now.

I agree with your assessment of technology & how it moves 100%. But there is more to all of this than meets the eye for the simple fact that we are all bottom feeders in the big wide world of CNC (and I'm OK with that). ShopBot is an entry level tool that offers one heck of a value in the marketplace. Before I bought my 1st Bot, I was looking at Techno & CamTech. The selling point for me was ShopBot's customer service, the fact that they listened to their customers needs & went well beyond the call of duty to make 'technical' and hardware accomodations. At least this was the case for me. None of the other CNC companies in this price range were motivated to speak to me at eye level or even listen intently to my requirements for a custom tool...or they lacked the technical know-how and confidence to convince me that they could deliver what I wanted. Additionally, ShopBot had the community of users that were willing to help me in a professional manner that just wasn't/isn't available from many home-grown users. I know when I get on this board, that I will get the right answer. I don't have to question the poster in my mind.

We've really got the magnifying glass out on this issue, so to put things into perspective, ShopBot will be around. Nobody does it better, and nobody in the marketplace has the value combined with expertise than ShopBot. The new kid on the block may get their controllers cheaper, but what about the entire software/hardware package? What about tech support? The majority of SB customers have never owned or run a CNC before, or they are businesses that don't have time to monkey around with science experiments...they just want something that works without breaking the bank. So while controls and alternative solutions on the hardware/control level continue to raise the performance bar & lower the price barrier, that doesn't quite show the whole picture. People motivated to tinker with their tool (like Mike & me) represent well under 1% of all of the ShopBot users out there. Isn't it nice to know that ShopBot cares about us too? I think so!

I think we should all step back for a moment and realize that very few companies in very few markets listen to what their customers needs are and address them as well as ShopBot has. If there was no passion or excitement for what they do, then the G4 would still be just a dream/wish. Does anybody on here honestly believe that Techno or CamTech would develop something like this to satisfy their existing customer's wish list? Yeah right! While ShopBot has done an excellent job of keeping CNC affordable, I thank them for not being tightwads when it came to the G4. If beancounters were running the show down there, we'd still be in the wish stage of things...I for one am extremely greatful and thankful that ShopBot is not run by beancounters and that they came up with the G4 to enhance our existing tools and give all of us tinkerers an interface that we can work with by pluggin in QUALITY off the shelf components. I do think that ShopBot's PR & communication on some issues should be stronger so that customers get that things are being done to make things better, rather than long lengths of silence.

While some of us could argue about controllers and possible shortcomings of the existing systems, I think we should step back and realize just how good we've got it! Everybody whines about Microsoft (Mike not pointing this at you ~ at all!) and how their software stinks or it locks up or it does this or that. Know what? For the price & feautures offered NOBODY does it better. Period. Their software, aside from what propaganda has been blared out in the media, is downright incredible for the money. So while we can compain about their software (don't get me wrong...it's not perfect & I hate some of the things it does too), there isn't anybody else out there that has done things as well as Microsoft all across the board. Run Linux, run Apple run whatever...I don't care WHO makes it...just give me the best all around choice for my hard earned money. I think that's what we are all looking for here & I'm glad that I bought the ShopBot because even 5yrs after having my tool, they still support it and are still driven to improve existing systems.

-B

[gerald_d]

For a long time the ShopBotters complained about chattery motion. ShopBot did not listen. Two alternative solutions were developed by individuals outside of ShopBot. Now ShopBot copies those efforts and will probably shoot the Ascension and Agek out of the water. Whose praises are to be sung here?

[richards]

Brady,
I think that we fully agree that Shopbot is a great company that offers a great bargain at an affordable price to those just discovering CNC routers as well as those who have carefully defined their nitch and have found the Shopbot to be a perfect fit. I've looked long and hard at other 'affordable' CNC routers, both before buying my Alpha and after. Just like you've pointed out, there is nothing else on the market that offers a workable machine, easy-to-use software, and an unsurpassed help forum.

My concern is not what Shopbot IS nor with what Shopbot WAS, but with what Shopbot WILL BE a few years down the road. Just this summer another company bought basically off-the-shelf parts (that anyone can buy), packaged those parts and offered that package as an upgrade to the PRT. Another company, outside the United States, not only packaged similar electronics, but also changed the design of the Shopbot to add features that they feel will improve the CNC experience. The principle people in both companies are highly respected by the Shopbot community. Even as I write this, there may be another dozen companies that hope to enhance the Shopbot by offering enhancements or clones. That's a cycle that seems to follow successful businesses all over the world. Shopbot is not immune to that cycle. My concern is that after significant movement was detected towards other companies, Shopbot announced products that compete head-to-head with these new companies - and there is nothing wrong with that. What I would really like to see is proactive movement from Shopbot instead of reactive movement. In other words, I would be much less concerned if I had full faith and confidence in the vessel rather than having faith and confidence only in the fact that the crew could patch leaks in the vessel as those leaks became dangerous.

There is one other point that confuses me and because I'm confused, I'm also concerned. I've followed the developement of Dirk's Agek unit as well as Ted's annoucement of the G4. It seems that there was very active participation of both Dirk and people from Shopbot in developing the Agek. Now the G4 is being promoted by Shopbot. Is the G4 a component part of the Agek or is it something that competes against the Agek? Or have I just totally misunderstood the role and purpose of the Agek and the G4? (I know that there are things that are none of my business and if this is one of those things, my feelings won't be hurt if somebody just tells me that it's none of my business.)

(Gerald, you're too fast for me. You slipped in while I was composing and basically posted the same question that I was thinking about.)

[Brady Watson]

Mike,
I don't have a clear understanding of the relationship between the AGek & the G4, and what agreements and business is involved in it. Unless Dirk cares to chime in and enlighten us, then it will have to be filed in the 'none of our business' folder...which I believe is where it belongs. Knowing ShopBot's business practices, I would give them the benefit of the doubt in doing the right thing and not stepping on anyone's toes.

Gerald,
ShopBot DID listen, but may not have implemented software and hardware changes fast enough for some people to be satisfied. That's going to happen regardless of what product comes under criticism. Things take time. I guess it's pretty much a moot point if you no longer run the ShopBot software anyway, with hindsight being 20/20. Let's pretend that ShopBot did copy either of those systems (copy is an interesting interpretation of listening to the market & co-developing one of the systems in question)...1) So what? 2) What are you going to do about it? 3) Happens every day all over the world. It's called business.

I think everyone's praises should be sung, in their own regard, no matter what hardware or software they are running. The G4 and the AGek are different pieces of hardware with distinct advantages between them depending on what you need to do with your tool. I have the highest regard for both Dirk & ShopBot and the time and energy THEY have invested in development for the benefit of us all. Why anyone on here would be critical of, or 'sour grapes' about the work that these guys did to benefit us all is beyond me.

-B

[richards]

I think that there are several Shopbotters that have ideas that they're developing that might enhance the Shopbot. Probably uppermost in their minds is the big question: "If I present this idea to Shopbot, are they going to evaluate my idea and come up with a marketing agreement if they think that my idea is good, or, am I going to see their version of my idea on the market competing against me?"

If the response is one of co-operation and little or no cross-marketing, then, I think, the Shopbot market will prosper and grow. On the other hand, if it's basically 'every man for himself', then I'm afraid that there will be a bunch of new little companies that fragment Shopbot's market and draw away customers.

As Brady said, "Things take time". Believe me, I know that the words 'quick' and 'marketable' should never be used in the same sentence. Things do take time. The FreeDoors program that Bruce Clark and I worked on a year ago took some serious time and effort. Without Bruce's ability to make the program usable, it never would have been used outside my shop (and maybe it still isn't). The point is that I did my little bit and he worked his magic and a program entered the arena.

Wouldn't it be better if 100 people each worked on a little problem than if 1 person worked on 100 problems? Wouldn't it be better, if an idea had merit, and if a product were introduced that reflected the quality and performance that Shopbotters expect, to co-produce that product, rather than have two competing products fighting for the same market share? The Shopbot market is fairly small, and if other 'botters are like me, they didn't buy a machine because they had an extra $100,000 sitting idle. Fragmenting that small market may very well distroy that market.

This on-going discussion about alternative software, alternative stepper drivers, alternative motors, alternative this and alternative that seems to point out that there ought to be a way to harness these ideas so that something actually comes of all the effort expended without everyone ending up in a free-for-all.

[dhouse]

Yikes!
All I ever wanted is a good clean cut. I have no idea about all the technical details that Mike, Dirk and Brady are talking about. But the " Shopbot Chatter" has been a problem from day one. It wasn't even addresed until Alan offered the Acension box and somewhere near that time Dirk offerd his solution . Hell, Gerald made his own box and an awesome looking router long before SB even offically responded to the cut quality issue.
I think that the SB silence on this issue is what opened the door for the other companies. Now we have options. We bought the Acension box and love it . Converting to GCode was easy. But now we are dealing with beefing up the gantry.
Gerald your system looks awesome! and I totally forgot where I was going with this
.
any how I see change is on the horizon and look forward to it.
DH

[richards]

Darryll,
You're right. This should be a discussion about making the Shopbot do what it was supposed to do all along. Endlessly tweaking this and that so that the machine does what a CNC router is supposed to do should never be necessary.

"Good enough" is rarely good and seldom enough. However, now that the ball is rolling and actual significant improvement has been made, let's just hope that it continues.

As a user, what are the minimum specs that I should expect? Let me start off with just two:

1). If a feature or spec is advertised, then that feature or spec should be attainable - meaning that if an 'accuracy' spec is given as +/- 0.015-inches and promotional videos of the machine show it cutting particle board full depth at 8-ips with a 1/4-inch cutter, then I think I should expect that I can cut particle board full depth at 8-ips and be within +/- 0.015-inch anywhere along the tool path. If the machine can't do that, then lets not say that it can. (Please note that I'm NOT saying that it can or can't hold tolerance to +/- 0.015-inch, I'm just using broad strokes to say that if the machine is advertised as being capable of doing something, or if a potential user would infer, after watching a promotional video, that the machine can do something, then the machine had better be able to do it. Period.)

2). "Chatter" is NOT acceptable. Period.

Anyone else have a suggestion/requirement?

[gerald_d]

3) Running in millimeters must be as good (or as bad) as running in inches. I don't permanently want to sit with a poor cousin of the main software.

4) The z-axis must never creep down.

5) The communication link (serial/USB/parallel,whatever) must be reliable. I musn't need to find "bridges" or put crocodiled ground wires onto the link.

6) If it is supposedly an industry standard CNC router, then it must read the industry-standard language, G-Code. Or:

7) It must seamlessly convert G-Code to its own language, including helices and arcs in vertical planes.

8) The control box must stay cool and be able to run with only annual maintenance in a dusty environment.

Those are just a quick few.....

[ted]

Wow ... I just had a look at this thread from my current location out here at the Kansas Camp ShopBot ... I think I know how Dorothy must have felt!

It would probably take the rest of the day to reply in any kind of reasonable detail. I'd just like to get a couple of things down ... just to get them off my chest.

We've been making ShopBots for over 10 years now. Since the first tools, our goal has been to offer the best performing and easy-to-use CNC that that we can, at the most affordable prices we can deliver. Performance for us has always meant two things, smoother and faster cutting, as/well systems that are as robust as we can make them. We work hard to make them work as well as possible. ShopBots are used by a wide range of people and in a wide range of applications, and we do our best to make them work well for all.

Life is not static, and we know we can always do better. Certainly it is the case that we are continuously working for smoother and faster in our tools. No, we are not yet as smooth as a $100K (though, now nearly as fast), but we are certainly working towards it and feel it is a reasonable target to hold us to.

There is some suggestion here that we are not "open" to suggestions/input from Mike. I don't get this. I have discussed gearboxes and belt-drives with you on several occasions. I have commented that I believe that a good belt box is a terrific way to go. I reminded you that all the first PR tools had belt boxes just like the one you have been discussing. I like them a lot as they work towards smoothness in two ways, the gearing and the dampening that that the system provides. At that time, we found that we could not make them reliably and affordably ourselves and we could find none on the market that were robust enough. So, we've stuck with what seemed to us the next best alternative, the low-backlash gearheads from Oriental. These have worked very well and quite reliably, I believe.

We tried again with belt-boxes three year ago and had several "single-plate" sets made up and tested. The single-plate approach make it possible to reduce the costs and simplify the belt-box a lot, and the concept seemed good. But as Mike has described, this one just does not stand up to the test of real use.

I have also discussed with several who post here that we have been considering gearheads for the PRTalpha tools. Even though the alphas can be set up for virtually any resolution of microstepping, it is hard to beat getting some of your resolution from gearing. This is because of tendency for microstepping to become nonlinear as loads and microstepping ratios increase. We have been experimenting with 7.2:1 PRTalphas at several sites (I know you guys have heard plenty from Brady on this).

I mentioned having discussed the issue of gearheads because we really have few secrets at ShopBot. Nonetheless, in terms of how we publicly post each item our develpment group is working on, our problem is finding some reasonable position whereby we don't create a huge amount of confusion in peoples minds about what the best selection or configuration of their tool should be when we haven't had a full opportunity to ourselves evaluate new developments or options.

In those cases where I discussed gearing, I explained that we had not decided whether the improvement this gearing provided would be worth the added cost. It is something we wanted to have a chance to evaluate, before we started pushing it. We, in fact, decided it is a reasonable option for some, and perhaps not worth the cost to others. So we recently started offering the 7.2:1's as an option with PRTalphas for customers who want added mechanical resolution for smoothness and/or for more cutting force. We will also make them available to any existing PRTalpha owners who wish to upgrade. (ShopBotters who have followed us over the years know that our policy has been to provide such upgrades to older systems at a price as near our costs as possible --- and this is also what we have done with the PRT 4g upgrade for PRTstandard owners.)

On the Gecko stuff ... I first talked with Mariss about using Gecko's on PRTs many years ago, at the time he was just starting to sell them. We built several PRT boards that used the first 201s. At that time, we had just undergone a traumatic business event. We had committed to a nifty little driver made by IMS for the first PRT tools. We had spent a lot of time working with IMS on both the board design and the deliverly schedule so that we could meet the demand for what turned out to be hunderds of PRTs in the first 6 months we sold them. The IMS committment to the delivery schedule was made over 4 months in advance of the first delivery, and we had repeatedly stressed to them how important the continuity of supply was (just as asside, we try to practice lean manufacturing). Two weeks before the first delivery, IMS reported all was on schedule. Then ... two days after the parts were overdue, when we had dozens of orders in hand for the new PRTs, we contacted IMS to be told that there was a delay and that we might receive a small part of our first shipment in about 8 weeks ...

Some of you may be able to imagine what a low point in all our lives here that little bit of information created. After repeated screaming, yelling, threatening, IMS did eventually provide us a small trickle of drivers (supposedly "from one of their customers who had extras") and we were able to get the first tools out while we frantically re-organized what to do for drivers on the PRT. Gecko was a possibility, but is was an untried supplier in California that we had no experience with, and also, or course, at the time we could not really run them fast enough to take advantage of their capabilities. We had always built our own drivers, so we quickly decided on that path, designed drivers, and boards, and within about two months were happily shipping PRTs ...

Now of course, we all know a lot about Gecko's. Marris has shipped a cajillion -- though I will not promise you they will never blow out. At the same time, the PRTalpha controller runs them well. We've known that for a couple of years and have shared it with many who were experimenting with other drives including Geckos (and we are all for experimenting and developing alternate systems, see the Developers/OEM page under Applications on the web site for current ideas). As noted above, technically the PRTalpha interface board uses a source driver IC. This is because it was a straightforward way run many PRTalpha drives on a single channel if someone wanted (note the multiple connectors on the board). This method does not work well for the Gecko, so the interface board for the Gecko works differently than than the interface board for the alpha, though we can share the same controller (again, see the Develper web page to see how we conceptualize these things). And, FYI as per the mention above, the pulse duration has been changed to exactly match the Gecko requirements (the alpha drivers do not care).

Hope a bit of this is useful to people. I'm late for Camp so it's back to Kansas. For those with PRTs, I do suggest considering the PRT 4g upgrade because the 2.5 improvement in step resolution provides an automatic improvement in smoothness, and of course, they go a lot faster.

-Ted

[richards]

Ted,
Your post cleared up a lot of misunderstandings. I want to personally apologize to you if you got the impression that I thought or stated that you or Shopbot was not 'open' with me. You and your staft have been most helpful in sharing information and ideas. Many of the facts and figures that you furnished were incorporated in modifications that I've made to my Alpha. So, again, I apoligize if you or anyone thinks that I am unhappy in any way with you or anyone in your company.

What does make my blood boil is why anyone thinks that the world needs two new controllers - namely the Agek and the G4. Those controllers are twins - or at least first cousins. If Shopbot and Dirk had independantly hatched the idea to make a new controller and then independantly - without knowledge or correspondance from the other party - designed and developed the new controller, then I would have kept my big mouth shut. But I know for a fact, that that was not the case. Why not work together and build one excellent controller instead of dividing the market and confusing the customer?

[elijah]

Hi,

I am planning to buy Alpha 120. I would be thankful if somebody could explain to me in simple english language, what I will get from ShopBot if I will order mentioned Alpha tool in October of 2006? Will I get machine which will not be able to make smooth cuts with its original control board and original software? What motor gearing will I get? What motor gearing should be for the best performance in V carving in 3D carving?
I understood that Ascension 1000 from custom cnc somehow could ensure very smooth cut, because it controls very well all three or four motors very well at the same time. That is all what I understood from my researches. And I am still absolutely unsure what kind of tool I will get. Maybe imedietely after receiving it, I will need to do serious upgrade of software and hardware??? Thank you.

Elijah

[steve4460]

If you buy the Alpha you will get a good mashine that will do the job if you dial in your feed speeds and have the right cutters. I have an alpha and I am happy with it .
Where are you located ?. See if there is anybody with an alpha in your neck of the woods and check it out .

[elijah]

Stephan,

I am in Lithuania. It means that I can rely only on ShopBot support and on the advices from forum.
Yes, I understand that the feed speed as well as the spindle RPM should be done according with material which I will cut and with the task, which I will want to do. From previous posts in this thread, I understood that some people was not happy with cutting quality of the their tools, and they began to modify machines. maybe it concerns only of old ShopBot machines? maybe all new Alpha machines are fine as well as its software?

[richards]

Elijah,

I'm sure that a lot of Shopbotters anywhere in the world would be willing to cut a part for you and then either post a photo of the cut or email you images. I will be happy to make a test cut for you, but my machine has been altered with a 3:1 belt-driven gearbox.

I'm attaching a GIF image of a test that I designed that exercises the Alpha in the areas that I was having problems with before I added the 3:1 gearbox.


407

I would be happy to email anyone a DXF file and the SBP file that I used to cut the test. The size of the test is 12" X 12". Cutting it out of MDF only takes a minute and, I would imagine, allmost every shop has a small piece of MDF left over from other projects that they could use to run the test for you.

[mikejohn]

One thing is puzzling me.
My PRT, which I have been very pleased with, consists of table, x rails, y gantry, z gantry, 4 stepper motors and associated cables, control box and software, including Part wizard.
The table I made myself.
I use AutoCad not PartWizard.
I can buy stepper motors of the shelf, and cabling.
The ascension 1000 makes my PRT almost an Alpha.
Mach software allows me to use industry standard G Code.
So all I am left with from the ShopBot are the x rails (which I can purchase elsewhere,) the y gantry and the z Gantry.
I do have ShopBot support for when it breaks down though.
Anyone got spare x rails, y and z gantrys going cheap?


...............Mike

[gerald_d]

Elijah, if I were you I would buy the PRT Standard instead of the Alpha. (I live in Africa). If you place your order now, your shipping date will only be in November (or later) and then the Standard should be shipping with Gecko drivers and geared motors. This will give the same results as the Ascension, and the cut quality will be better than the Alpha of today. Maybe not exactly as fast as the Alpha, but close. It will cost less and use less electrical power.

If you find that the millimeter version of the software doesn't work for you, or if you have problems with computer communications etc., you can convert the control to Mach3 for probably less than $200. Then you will have the choice of support from either the ShopBot, Ascension or Mach forums, and your machine will be similar to other Gecko machines already in Lithuania - somebody there will understand it, and you should have a good re-sale value there.

[gerald_d]

Mike, I have those bits lying around the shop - come and collect.

[richards]

Mike J.,
You've nailed the problem pretty good. It all comes down to service and software.

Shopbot's service is unparalleled. Their forum lets any 'botter help any other 'botter. Opinions and tips are freely posted including most that would be critical of some aspect of the machine. Sometimes some of us get a little carried aways with our posts and the forum admin helps us avoid serious embarassment by deleting something - I've had that happen to more than one post - but they're a lot more tolerant than any other forum that I've visited.

Everytime I've called Shopbot for help, I've gotten help - and everytime that help was exactly what I've needed. Everytime I've emailed, I've gotten a reply that solved or helped to solve the problem - including several emails from Ted who personally gave thorough answers to my questions. I don't remember ever needing parts from Shopbot, but they've had every part that I've ever asked them about - on hand and ready to ship. To me, that is excellent service. I don't know what I would expect more than that.

Their software is easy to use - period. Whether it is industry standard or whether it is not doesn't matter to me because I can use it to do the things that I need to do. I have G-code. I know how to use G-code. I also know that G-code has built in features that are lacking in Shopbot's code, but I still use Shopbot's code. It works for me and it works very well.

Except for 'chatter' the Alpha that I have has surpassed my expectations. It is fast. It is sufficiently accurate to do what I need to have done. It is robust. It is simple to maintain and repair. Did I mention that it is fast? It is fast. I found a way to solve the 'chatter' problem by adding a 3:1 belt-driven gear box. Brady mentioned that Shopbot now offers an excellent gearbox to anyone who purchases a new Alpha and a retrofit to existing customers. In my opinion and with my experience using the Alpha, I'll go on record to plainly and loudly state that the Alpha needs a gearbox or you'll have excessive 'chatter'. Adding or buying a gearbox is not a big deal. Although I don't know what a gearbox costs from Shopbot, building one yourself won't break the bank - and it turned my machine into a real CNC router.

Everything else that you posted is perfectly valid. Parts and pieces to make or modify a CNC router can be purchased from a lot of different places - but who's going to hold your hand while you assemble your machine. Who's going to help you cut your first parts? Who's going to rush to your aid when you realise that you simply don't know what to do next?

I would suggest that anyone contemplating entering the CNC router world first buy a Shopbot. Learn how to use it. Learn what it can do. Learn what it can't do. Then, if your needs fall outside of what a Shopbot can do, sell it and buy something else. For the money spent, I can't find anything else on the market that even comes close. Right now, if I were to need a second machine, I would buy, at the very least, the complete machine from Shopbot without electronics of any kind and then add those parts and pieces that exactly fit my needs; but, remember, I've built process control computers for more than thirty-years so messing with the electrical part of a machine is something that I have done and enjoy doing. I don't recommend that anyone else try doing that. It could very well end up costing you much more, both in time and money, than buying everything from Shopbot.

Shopbot has a good machine - no - Shopbot has a great machine. If it can't do everything that you need it to, it can be adapted or modified until it can do what you need it to - unless you just have to have one of the big-iron machines that cost 10X to 30X more than the Shopbot.

[mikejohn]

Other Mike
I agree 100%
"I would suggest that anyone contemplating entering the CNC router world first buy a Shopbot. Learn how to use it. Learn what it can do. Learn what it can't do. Then, if your needs fall outside of what a Shopbot can do, sell it and buy something else."

It's when you realise what is possible, and what isn't possible from Shopbot, that you start taking notice of these, for me, complicated posts.

...........Mike

[richards]

One of the interesting character traits that I have is that I find it really easy to blame someone else for my problems. Back when I was having problems with my 3hp Colombo spindle, I called Shopbot a few times to see what to do. They gave excellent advice. The spindle still didn't work right. I called PDSColombo. They gave excellent advice. The spindle still didn't work properly. As one point I started checking my family tree to see if perhaps I had an uncle Luigi, who drove a big black car and who liked to carry baseball bats when he visited with people, who might be willing to visit Shopbot for me and politely ask why they sold spindles that didn't work. As you all know, it wasn't Shopbot's fault. It wasn't Colombo's fault. It was my fault. I had modified my computer and added a wireless network card that interrupted operation of the software. It was my fault. But, during my problem, Shopbot went out of their way to try to help me. Of course their solutions didn't work for me because they had never had to deal with something that I had created before. How could they solve my problem? But they tried.

The other major problem that I fought for two full years was 'chatter'. I've posted photos of the 'chatter'. Others have posted photos of 'chatter'. I talked to Shopbot about the problem. They again tried to help. Nothing worked. Nothing. I checked rollers. I cleaned rails. I removed and inspected spur gears. I played with ramp speeds. I tested every kind of cutter that I could find. I examined the mechanics of the Shopbot's design. I called Bishop-Wisecarver and talked to their technical people to see if I added their rails or more rails or bigger V-rollers would work. Finally I realized that most PRT owners didn't admit to having 'chatter' problems. I thought, "what a conspiracy. They've all gotten together to get their revenge on us Alpha owners by denying that they have chatter problems." Then, after thinking and pondering and thinking some more, I realized that most PRT machines were geared. Then, I called Oriental Motor to order gearboxes for my Alpha motors. They couldn't help me. Either you bought Alpha motors with the gearbox already attached or you bought or built your own. Sorry. That's just the way it was. So. I built my own belt-driven 3:1 gearbox. Then I built version two. Then I built version three. Then I built version four. Now I don't have chatter. There was nothing wrong with the rails. There was nothing wrong with the rollers. Their was nothing wrong with the basic design. The Alpha motors just had to be geared down to give proper operation on my machine.

The important factor in all of this is that Shopbot tried and tried and tried to help me -even when it wasn't their fault. When it was their fault (at least I'll call it their fault) they still tried and tried and tried to help me. Because they tried and tried and tried, I really admire them. There are issues that I don't agree with. Many of you have read my rantings about those issues, but that does not mean that I would buy from anyone else. Some of you may have read my postings about the Ascension box. I like it, but I don't own one. You also know what I've said about G-code. I like it, but I don't use in on my Shopbot - and I don't think it is the coding language that a new CNC router user should have to use. Maybe I've underestimated the ability of new CNC operators to learn new and complex things. I don't think so. My memory is going fast, but I do remember wondering just how long learning to use a Shopbot would take - and that was with their easy-to-use language. I don't have a PRT, but if I did, I would be talking to Dirk right now to order his Agek. He's built a good box. He's built the box the way that I would build a box. IF I found something that I didn't like about his box, I would be calling Shopbot to order a G4. It's nice to have a choice. It's nice to know that there are options available. It's nice to know that I'm not doing this alone.

By the way, does anyone really think that Thermwood or Komo or any other CNC router has no problems. Does anyone really believe that buying a big-iron CNC router means that a service tech drops by twice a month just to see if everything is working - at no cost?

We Shopbot owners have got it pretty good.

[elijah]

Gerald_D, is this mean that PRT now is better than Alpha? What for then was created Alpha? I always thought that Alpha is created for more precise and fast cutting, carving etc. In other words Alpha should do the task better than standard PRT. I am completely confused. I do not have goal to save a bit of USD. I am keen to buy good tool, if we talk about ShopBot tools. What I should do then...

[elijah]

Mike Richards,

If I understood, you are very happy with your Alpha. The only thing is that you changed a gear box. Is this mean, that if I will be ordering my Alpha, I should ask ShopBot to equip it to me with your mentioned hew gear box?

Thanks.

Elijah

[richards]

Elijah,

Gerald gave very good advice. If you buy the PRT model with Shopbot's new G4 board and Gecko drivers, you won't be disappointed. If you decide to buy the Alpha, be sure to talk to a lot of users first. In my experience, there is nothing wrong with the Alpha that a good gear box won't solve.

Look at some of the photos that have been posted showing the smoothness of the cuts - or the lack of smoothness. Ask Brady about his geared Alpha. Ask me about my geared Alpha. Ask Pat Fulghum about his non-geared Alpha. Listen carefully to the answers and then read Gerald's post again.

(Elijah, you posted while I was composing a response to your previous question to Gerald. But yes, I would ask Shopbot to configure a new Alpha with the gearbox option. I don't know exactly what they offer, but I think that Brady uses a 5:1 gearbox and I think that he's talked about a 7.6:1 gearbox. Mine has a 3:1 belt-driven gearbox that works perfectly for me.)

[gerald_d]

Elijah, I am also confused by all the reports! So please get some more opinions. My personal choice would be for Standard over Alpha. But maybe you are the type of person who prefers a sports car with hard suspension over a standard car with comfortable suspension - is the one "better" than the other?


Tell us what type of work you want to do? That is very important in selecting the right tool for yourself.

[elijah]

Mike,

I am wondering what is the standart gearbox which goes with Alpha today? Or have I ask the ShopBot support?

Thanks.

[steve4460]

The alpha has no gearbox , but you might be able to order it with one .

[elijah]

Gerald,

If we talk about the cars, I prefer good SUV with sport car characteristics (say, Touareg 3.0 TDI or V10 TDI or Porsche Cayenn). In other words, cars which are comfortable as well as good for active driving. I really don't like stiff suspension cars, because our roads are not perfect.
But it is difficult for me to see analogue between such comparison of routers and the cars. Also I have a feeling that I want to get really good equipment. If I would live in USA and near the ShopBot office I could try the cheapest router, than to change something or upgrade it. But in my case, sending of all heavy hardware from USA to Lithuania costs money, so I would like to choose just a good reliable device for 3D carving and V carving and to avoid modifications of hardware (motors, gearbox etc) if it is possible, of course. As far as I see my future, I am not planning to do high volumes of cutting MDF and making so called economy class furniture. It is more about hardwood products with carvings. Also I feel that you are skilled masters in this sphere, so you can get the best results with less tools. It is like Nicolo Paganini was playing on the violin with one string only
. I would like to have a good tool from the very beginning and then to start to learn to work with it. That is why I am considering Alpha with 5HP colombo spindle. But things are not as simple as I thought

[elijah]

Stephan,

Is it good or bad, that, Alpha has no gearbox? People in this thread was telling (if I understood correctly) that it is shortcoming of the Alpha. Should I understand that absence of gearbox on Alpha doesn't allow to get smooth cuts? What about carving? Sorry, maybe my questions sounds like "how to ride the bicycle?" and answer should be - "just try many times, and you will learn".

[elijah]

Stephan,

Is it good or bad, that, Alpha has no gearbox? People in this thread was telling (if I understood correctly) that it is shortcoming of the Alpha. Should I understand that absence of gearbox on Alpha doesn't allow to get smooth cuts? What about carving? Sorry, maybe my questions sounds like "how to ride the bicycle?" and answer should be - "just try many times, and you will learn".

[richards]

Elijah,

It's a very bad thing that the Alpha does not have a gearbox. Without the gearbox, the Alpha 'chatters' (makes rough cuts). With a gearbox, there is NO 'chatter' - at least on my machine.

Before I installed 3:1 gearboxes, I had chatter at all speeds from 1-inch per second to 10-inches per second. The chatter was just as bad in my V-carved plaques as it was in MDF cabinet parts.

You'll have to send an email to Ted Hall at Shopbot and ask him about pricing and availability of an Alpha machine that has Alpha motors with gearboxes. I don't think that they've published any prices yet. Brady Watson might also know the price and availability of a 'geared Alpha'.

[elijah]

I read carefully Ted's post here and found that he is talking about new gearing (7.2:1) for the Alpha, as the option for extra quality. As I understood it reduces speed of movements along axes, but increases torque of the motors, and provides mechanically very smooth motions, which gives, as a result, better cut quality. I hope I understood correctly

[elijah]

Maybe somebody already tried that 7.2:1 on Alpha and can say what are results in terms of smooth cut?

[steve4460]

All I can say is I am happy with the way my alpha works , the customers are happy too.
You may have to play around with the cutters and the speed depending on your material to get what you want . I am using onsrud down and upspiral cutter and they work for what I am doing with it .Lets face it even a table saw leaves marks on the edge . As to doing V carving , it works nice too. The PRT's make a lot of noice when you run them slow , I know this becouse a freind has one and I have seen it run . So in my book , if you got the money then go for the alpha .
Thats just my 2 cents

Bot on

[ger_d]

"The PRT's make a lot of noice when you run them slow , I know this because a friend has one and I have seen it run."

....but from November they will be as quiet (quieter even?) than an Alpha

Elijah, if you are not going to be slicing boards with long straight cuts, then the extra speed of the Alpha will not be visible to you. When the Alpha does small curves it goes at the same speed as any other ShopBot.

[elijah]

Thank you Gentlemen. I will take the notes.

[ted]

This is a follow-up note relevant to my earlier posting above.

We spend much of the day at ShopBot communicating with, training, and supporting ShopBotters. When we are talking and interacting we try to be open and share everything we know, whether it be helpful expertise, or information about ShopBots or ShopBot. So we were a bit taken aback by recent suggestions on the forum that we have not been communicating well. After a little reflection, I appreciate that we could probably do a better job of publicly reporting, as much as is reasonable, what’s going on at ShopBot and our thoughts and reflections on things.

As one step in making information more available, what we’ll do is start regularly reporting on what’s happening at ShopBot in a monthly blog. We’ll try to report on current development projects of interest as well as address any issues of concern that come up in the forum. I’ve been working on the first blog, and hopefully will get it posted in the next day or two.

[paco]

Woohoo!! More about what's going on at ShopBot!

[jhicks]

I haven't read this post for some time and find its filled with way too much techno babble for me but no doubt helpful for those who appreciate that sort of stuff. Clearly there is a lot going on with new technology and adaptations which I percieve as healthy and positive.
My reasons for this post are that Mike Richards mentioned my experience with Ascension way back mid way in this post. I know Mike from Free Door work and admire his contributions so Thanks Mike for the kind words.
As for me, I don't have the time, talent, or inclination to be developing mechanical or electrical solutions for equipment I purchase and use. Hats off to those who do. After several years with my PRT and 2 months with the Ascension conversion, I can only say I'm integrating well, understanding better, getting excellent support, and very happy with the tremendous improvement in results as measured by the glide vs jittery gantry moves,quiet and efficient moves, substantially higher speeds easily approaching or exceeding alpha with the old 1AMP standard PRT motors, no interruptions or files lost, and the resultant wonderfully smooth cuts in fewer passes.
I really have no way to compare to any of the above mentioned modifications or variants in above posts except what my personal experience has been with the PRT vs new Mach and Ascension.
So to reply to Mike's post, I did post a follow up explaining in more detail about my frustrations, conditions at that time, and my update along the way having been into it now for about 8 weeks. I'm done experimenting, Never done learning, and not able or qualified to enter the entire techno debate to see how I might come up with a better mousetrap. Plenty of other professionals out there to do that.
All I know is while the debate continues, we're doing what we need and want to do. Make the machine do what we want, at 2 to 6 x+ the old speeds or more, deliver quality cuts consistently , and make the machine do what its there for: PRINT MONEY.
That's what we have it for and its doing it better than any adaptation I ever seen or been made aware of in this level machine in any camp or meeting until/except Kansas.
G code is now my friend. I just had to take some time to introduce myself to it and learn about the power of this standard and glad I did.
I have great admiration for all the folks at Shopbot and am pleased to see this major user debate being addressed. I hope the G4 is fantastic and trust Ted and all at SB will continue to make it better and better. Just had to put in my 2 cents on Mike's post from my initial experience and commend you all on your ongoing commitment to developing new and better resources.
We will always admire and work with shop Bot in mind and expect new advancements in the future like G4. While these are being designed, tested, debugged, and delivered we simply want to be running excellent quality, at higher speeds, with more flexibility, at lower costs. That's the world we live in here and I'm happy we have made progress toward that goal.

[harold_weber]

This is a follow-up to my October 4th post in this thread. There were three suggestions made by folks to improve the cut quality I showed. I have results from trying those three suggestions.

1. Check pinion gears for wear. Below is a new photo comparing the "old" and "new" pinions. I had changed the pinions when I changed to the 7.2:1 gearboxes, but my opinion is that the "old" pinions do not show enough wear to cause any degradation in cut quality. I clean and regrease the gears frequently, if you don't your results may differ.

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2. Check for dirt on Vee-rollers
3. Check for dirt and rough machining marks on rails.
I DID find some dirt on the rollers, but it was more like a stain or film. After thoroughly cleaning rails and roller grooves, I cut another test piece and did not see any improvement in the cut quality. Here is a photo of the surface finish of the X-rail:

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The rails looked good in my opinion. Other machine rails manufactured at other times may have different surface finishes.

Finally, I enlarged the same photos that I posted on October 4th, and you may be interested in this enlargement, which is the top portion of the maple cut quality comparison photo:

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At this level of detail, you can see the individual tool marks resulting from the 0.010 inch per rev feed rate (chip load - single flute bit). After seeing this, I'm pretty satisfied with my machine. Your results and opinions may differ. If you are able to share photos and care to share the techniques you use to get still better cut quality, I'm sure you will find an appreciative audience here.