Interesting ShopBot Blog Post (12/07/18)

[coryatjohn]

I just read this interesting blog post from ShopBot. It has a number of points that contradict the opinions of experts that post on this forum.

Anyone want to "fact check" this post?


Why We Build Our CNC Tools the Way We Build ‘em (http://www.shopbotblog.com/2018/12/build-cnc-tools-way-build-em/)

[Gary Campbell]

So.... John,
Because the written word, without tonal inflection can be easily misinterpreted, I need to ask: Since there appears to be differing opinions, which side would you believe to be more true? The link you posted or the opinions of those you refer to as "experts"? Personally, I have seen a good number of knowledgeable guys here, but none would consider themselves an expert. That said, most of them work in the real world using these machines and for the most part would disagree with the majority in that article.

Myself, I would relish the opportunity to publicly debate Mr. Hall on these exact points. As I did when I worked for the company based on the first time he published that same spin: http://www.shopbottools.com/mProducts/ShopBotdesign.htm As you can see, this is simply regurgitated marketing hype with a few more modern "buzz words" and "catch phrases" added for effect. That first conversation ended in a draw with an agreement to disagree. Since that time, and especially not being an employee of the company, I believe that most every position in the original publication, or published specs here: http://www.shopbottools.com/mProducts/PRS_specs_compare.htm can be disproven using a combination of manufacturers data, engineering calculations and some real world testing combined with common sense. Did I mention that to ensure truth and fairness, I would require a panel of 3 impartial engineers to fact check both sides?

For example the rated maximum speed. Advertised at 30"/sec or 1800"/min. Having owned 2 PRSa machines I can tell you that you can set them that high, but unless you crank the current much higher than the factory recommended settings, they will never achieve that velocity. Even then, on an 8' table there is a very short period of time spent at max velocity as most of the real estate is chewed up during accel and decel. And then there is Oriental Motors max rpm for the AS and AR98AA7.2 motors of 250 RPM. With a 30T pinion that has a pitch diameter of 1.5", a pitch circumference of 4.712" 250 RPM yields 1178.09 "/min or 19.6"/sec. The "published machine specs" show numbers more than 50% higher than the mfgr of the motors say they should be run. What are they set at when they leave the factory? My guess is even lower than the 19.6"/min rated max.

And while we are at it, for those with a PC router and a ShopBot standard, lets see a show of hands who can cut 600"/min in anything other than air? It isn't very likely to be done 1/4" deep in box store insulation foam. The list goes on and on, but I can't.

I'm over it. I'm sad. Just the fact that this regurgitated spin has been brought back to life after 6 or 7 years with improved graphics and even more catchy phrases is proof that things in Durham are not well. Desperate times call for desperate words, I guess.

[JimmyD]

I don’t consider myself an expert, but I do have two engineering degrees (one of them being mechanical engineering) and 35 successful years in the aerospace industry. With that as my pertinent qualifications, I’ll challenge a simple one of the claims to start.

The blog post states “We avoid welded joints that can become distorted with time......”. That simply isn’t true. Welded joints that are properly designed and manufactured don’t change over time or they weren’t designed using industry standards and/or weren’t manufactured with proper techniques and materials. There’s a reason that the frame in my Ford truck is fully welded and not bolted together. It is rigidity and strength.

Jim

[woodshop]

30 to 75"/min is our speed range here. (Desktop with router cutting maple ply)

[dlcw]

After 10 years of using my PRSAlpha and going thru every tuning tip I can find, I can say that there is STILL a lot of inherent flex in the PRSAlpha. Other experts on this forum have shown me ways to develop cutting strategies that help compensate for this flex. They do significantly increase cutting time, thus loosing me money, but the cuts are very clean. When you watch a machine change directions and the whole machine shakes, you know it's NOT very rigid.

The claim to make things backward compatible is a half truth. Years ago, Shopbot and Thermwood worked together to develop an interface program between Thermwoods eCabinets software and Shopbot CNC's. It was and still is the backbone to my cabinet business. However, I am stuck at the 3.6 versions of SB Control software because upgrading to the 3.8 versions would break the SBLink compatibility, thus putting me out of business. Another problem I had with control software over the years was that when released it was never ready for production use. It went thru several bug fixes to get it close to production ready. I'm sorry, I'm not a beta tester. The software should be 100% bullet proof when it's released.

The one thing I didn't see mentioned in the blog article was the VERY weak link of using USB communication technology between the control computer and the CNC controller. This has been and will continue to be a VERY weak link in a Shopbot solution. Something needs to be done to eliminate the constant "lost communication" problem. Sorry Shopbot, but most of us don't work in a clean room. We work in dusty, staticy environments. That's a fact of production shops. Shopbot has still done nothing to address this problem. Having an electrical engineering degree so you can develop a good grounding system for your PC, CNC Controller, CNC machine and dust collection system should not be a prerequisite of owning a CNC machine in a wood shop. I was lucky in that my background was 23 years in electronics in the Coast Guard where I learned all about good grounding systems and how to implement them. I would surmise that most folks on this forum don't have this kind of background so the lost communications error problem is incredibly frustrating. After 10 years owning my CNC there is still NOT a solution to this problem. Shopbot FIX THIS DAMN PROBLEM!!!!

[coryatjohn]

I find my PRSa to be an excellent and reliable machine FOR MY PURPOSES. That said, I noticed a curious thing the other day. I was aligning the X axis for use with the indexer and had a wrench balanced on my zero block (a 2x4 about 10" long) on the indexed bench. I was moving the X axis in .01" increments and the tool started wobbling back and forth considerably. Granted, I had been moving the tool a number of times and a harmonic had set in but still, moving the X axis .01" caused the entire machine to vibrate noticeably. Curious.

[Gary Campbell]

John...
Is this a recurring issue or a one off anomaly? If recurring, do you have a video or a set of actions to recreate? This does not seem to be something other than rare and has my curiosity up. There has been some oddities in the keypad operation since the modifications were made for the desktop, but yours is a new one.

[srwtlc]

Yeah, if you're doing a fixed keypad nudge with the right settings for the fixed amount and get a good button press rhythm going, you can get a strong jiggle going. Especially in the X axis.

[Gary Campbell]

Yeah, if you're doing a fixed keypad nudge with the right settings for the fixed amount and get a good button press rhythm going, you can get a strong jiggle going. Especially in the X axis.

Really??? With a bit of a tuneup even a PRS standard will fly: https://youtu.be/33gLcfC59pA

[Brady Watson]

With a bit of a tuneup even a PRS standard will fly: https://youtu.be/33gLcfC59pA

That thing totally rips for a Standard. I've never seen a ShopBot running SB electronics (including an Alpha) move like that. I always wished they would though. Pretty impressive considering that controller is less than $300, including cables and power supply.

Better. Cheaper. Faster. American. What's not to like? ShopBot should just use these and quit fooling with outdated ideas and tech. It's just better in every way. The wireless MPG is pretty sweet.

[coryatjohn]

John...
Is this a recurring issue or a one off anomaly? If recurring, do you have a video or a set of actions to recreate? This does not seem to be something other than rare and has my curiosity up. There has been some oddities in the keypad operation since the modifications were made for the desktop, but yours is a new one.

Gary - Since I was moving the X in only .01" increments, and must have been hitting the keypad just right (maybe 1/2-1/3 second increments) so it got into a harmonic vibration with the natural frequency of the entire machine, I would say it would be recurring and could reproduce it. It kind of surprised me. That means the machine itself was flexing enough to nearly knock the tool off the zero block.

It was just a curiosity and I've never seen that type of vibration during an operation.

Here's a picture of my indexer setup.

32305

[bill_l]

I certainly see one problem here ... not a darn bit of debris anywhere! No chips, no dust no nada.:rolleyes:

[joe]

Bill, I agree it doesn't look right without a few chips laying around.

Let me post a belated Thanks to Gary C. for his continued assistance and support. His post latest post, https://youtu.be/33gLcfC59pA under scores the potential with this equipment. He's a gold mine in experience.

[EricSchimel]

Bill, I agree it doesn't look right without a few chips laying around.

Let me post a belated Thanks to Gary C. for his continued assistance and support. His post latest post, https://youtu.be/33gLcfC59pA under scores the potential with this equipment. He's a gold mine in experience.

That's me in the video Joe :rolleyes: But I do agree, Gary knows his stuff.

[coryatjohn]

There are no chips or dust because I clean up my shop before I start a job and after I complete one. I am fastidious about it. My machines, all of them, look brand new. Anyone looking in my tool boxes would swear they are right out of the packages and never been used. My father taught me that when I was 5. Clean tools are happy tools. Make fun of my shop all you want though. You can walk barefooted with your eyes closed and never so much as pick up a grain of dust or a chip of material.

My garage is the same way. It's so clean you can eat off the floor.

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[EricSchimel]

That's impressive. I certainly don't have that kind of discipline!

[Bob Eustace]

There are no chips or dust because I clean up my shop before I start a job and after I complete one. I am fastidious about it. My machines, all of them, look brand new. Anyone looking in my tool boxes would swear they are right out of the packages and never been used. My father taught me that when I was 5. Clean tools are happy tools. Make fun of my shop all you want though. You can walk barefooted with your eyes closed and never so much as pick up a grain of dust or a chip of material.

My garage is the same way. It's so clean you can eat off the floor.

32309

Magic John! All you need for perfection is a couple of Teslas and a nice Powerwall blinking away!

[bill_l]

Dito the "impressive". I too try to be as meticulous but have not achieved your level of perfection.

[dlcw]

I'm not sure it's a matter of discipline or a matter of having the time available to do such a thorough cleaning. As soon as I finish a project, I start a new one (many times while I'm still working on the previous project). I'm currently booked out 6 months. I tune up my machines (change blades, etc.) when I get a chance but the machines pretty much look like they reside in a production woodshop without a dedicated cleaning crew. I try to do a blow down once a year on a windy day in the summer to get most of the dust out.

I used to keep my shop spotless when woodworking was a hobby. But now, if I'm cleaning, I'm not completing customers' projects and I don't get paid. At the point, the lights get turned off..... My garage has a gravel floor so I'm not to worried about keeping it clean. LOL....

[coryatjohn]

>> I'm not sure it's a matter of discipline or a matter of having the time available to do such a thorough cleaning.

I'm sure that's the case. One thing about continuous cleaning. It takes very little time to keep things clean if you're always doing it. Leaving things for a once a year cleanup would certainly take the fun out of it. The tolerable level of contamination in a shop environment is a personal preference more than anything.

[scottp55]

Practical aspect also.
Had a friend lose his entire shop to fire....hand carver, but all his big iron was downstairs in the basement, and chips,shaving,sawdust accumulated bit by bit in nooks and crannies...THEN a squirrel chewed through his 220A insulation and fried itself...starting the chips on fire. Who knows...it may have burned anyways, but chips certainly didn't help.

Constantly think about another guys shop 20 years ago, and a drying oil rag got covered with sawdust so he couldn't see it when he swept partially....Poof!:(

And then James McGrew's "Barrel Fire"....darn good thing it was in the middle of a clean concrete floor!

[bking1836]

The one thing I didn't see mentioned in the blog article was the VERY weak link of using USB communication technology between the control computer and the CNC controller. This has been and will continue to be a VERY weak link in a Shopbot solution. Something needs to be done to eliminate the constant "lost communication" problem. Sorry Shopbot, but most of us don't work in a clean room. We work in dusty, staticy environments. That's a fact of production shops. Shopbot has still done nothing to address this problem. Having an electrical engineering degree so you can develop a good grounding system for your PC, CNC Controller, CNC machine and dust collection system should not be a prerequisite of owning a CNC machine in a wood shop. I was lucky in that my background was 23 years in electronics in the Coast Guard where I learned all about good grounding systems and how to implement them. I would surmise that most folks on this forum don't have this kind of background so the lost communications error problem is incredibly frustrating. After 10 years owning my CNC there is still NOT a solution to this problem. Shopbot FIX THIS DAMN PROBLEM!!!!

Amen! I’ve lost weeks of productivity in my first year of ownership thanks to position loss from electrical interference. ShopBot support has been diligent and eager, but I suspect the root problem isn’t “solvable” until they improve their whole approach to coms.

[erik_f]

Gary,
He mentioned you built the control box, but he also mentioned he is running belt drive transmissions. Are those something you offer also? I would love an easy option to ditch the gearboxes.