What to buy

[sebastien1]

Hello all,

I am looking to add CNC router to my 1.5 man operation. This years IWF show add a few to choose from, however I'm drawn to the Shopbot for its low start-up cost and easy upgradeble features. I plan to use the machine for 1/2" & 3/4" veneer ply casework (kitchens and built-in's) and possibly other things once proficient programming and operation skills have been achieved.

So here's what I'm looking at: the PRS standard 96-48-6 w/ HSD 2.2 HP or maybe HSD 4.0 HP spindle. All this for about $13k.

Speaking with the manufacturer everything I want to do can easily be done, just a bit slower. From those using a Shopbot Standard for cutting out cabinet parts, routing dado's, drilling holes, etc., what is the truth about this set-up? Can it handle it? Thanks...

[beacon14]

My understanding is that the standard model will "handle it", but you will be limited to somewhat slower cutting speeds, which could translate into shorter bit life. Also, for production cabinet work a second Z axis or dedicated drill is highly recommended for hardware and shelf pin holes. A drill can be piggy-backed onto your spindle, but a second Z axis would require a 60" wide machine to be able to reach an entire 4x8 sheet with both spindles.

What sort of hold-down method are you considering?

[sebastien1]

David, thanks for the reply. I don't really think the slower speeds will be that big of deal for me; at first. I know I can upgrade to the Alpha... one of the selling points...
Is the recommendation for the second z axis solely based from a time savings perspective in tool changes?

As far as holding; I would like vacuum hold down but to start off it will have to some kind of manual method, using the tabbing system. I know there are a few building there own system's which may be an alternative. My main focus to get just enough to get the job done at a relately inexpensive cost.

[beacon14]

You can indeed add the vacuum later. Yes, the 2nd Z or air drill is to be able to do all your cutting and drilling without having to change bits twice for each sheet. Being able to keep a 5mm drill bit in the air drill and a router bit in the spindle is what makes it possible to cut cabinet parts efficiently in my book.

[bcondon]

The reason I purchased the Alpha is that I hope to cut large parts. As I was told in class, there is no feedback loop so the standard knows where it is suppose to cut but can not tell if it got there or not. If you drive it too hard, then it will not get to the finish location in time and then the next position will be delivered so you will have an incorrect cut.

I was thinking Kayak parts which can be the size of cabinet parts. I spent the extra $5K because materials and time (catching up on mistakes) is expensive.

You can purchase the standard, and try it.

If you are having issues, then the price to upgrade to the alpha is $6K, which is 1K for a bad choice but at least the Shopbot folks give you a reasonable way to escape your decision.

[sebastien1]

Bob, I'm slightly confused by the 1st paragraph you wrote. Are you saying that the "standards" drive motors can not keep up with the software? If so, this is exactly what I need to hear. I was under the impression that the only difference between the "standard" and Alpha was the cutting force and cutting speed.

I assume that it would take 2-3 passes to through 3/4" Maple veneer; would the "standard" have a problem finding the same start and finish point? Would it not leave a perfectly smooth cut or would it be a staggered stair step looking cut? Many thanks..

[Gary Campbell]

Sebastian...
In addition to the additional cutting speed and force, the Alpha uses closed loop steppers. What this means is every step (partial revolution)of the motors is fed back to the software insuring exact positioning. If pushed beyond it limits, (usually by too aggressive cutting) the standard could "loose steps" which would result in the bit being in a position different than the software assumed. Hope this clarifies.
Gary

[sebastien1]

Gary thanks for the clarification. So, for example, as long as you don't try to cut through 3/4" maple veneer in less than 2 cuts there should not be a problem.

Exactly how many passes does the "standard" need to effectively cut through 3/4" material? I assume this is based from the sized bit being used and spindle hp.. Say its a 2.2 HSD Spindle and a 3/8" bit? What is recommended?

[Gary Campbell]

Sebastian...
I can't answer that question as 1) there are too many variables and 2) I have only cut with an alpha. For professional use, I can only reccommend the Alpha and spindle combination.

If you take the wages that your 1/2 man makes in a year, and spend it on the top of the line ShopBot, assuming early proficiency, your machine, as ours was, will be paid for in a year with advanced capabilities and increased production.
Gary

[sebastien1]

Gary, with your Alpha which spindle and bit are you using and how many passes does it take to cut 3/4" Maple veneer?

To be honest I'll probably end up with the Alpha. Just seeing if I can get away with less upfront. Adding a CNC vs. hiring another body is the better choice. It hasn't been the greatest of years and upcoming projects are somewhat light. So I figured the slow time could be well suited for the CNC learning curve.

[Gary Campbell]

Sebasien...
I use the 4 HP HSD. We will be adding a 2.2 shortly. I usually cut with a 3/8 mortise compression bit and 2 pass at 4+ips or single pass at 2ips depending on material. I tried 1/4" but the bits bend too much when pushed. Other bits may cut faster, but the mortise compression does the best job on the 2 sided veneers.

Your hold down method will be the limit, dont forget to budget for some hold down method. That is another advantage of the MC bits. It packs the cut slot with chips and results in less vacuum loss.
Gary

[sebastien1]

Gary, you will be adding the 2.2 spindle on the same machine or another. Doing you think the 2.2 would be sufficiant for cutting 3/4" veneer? Does a mortise compression bit have both upcut and down cut?

[richards]

I have a PRT-Alpha with a 3hp spindle, but I still usually make three passes in plywood. One pass is at about -0.30 inches, climb cut. The second pass is at about -0.60 inches, climb cut. The third pass is at material thickness -0.025 inches (the 0.025 "skin" is so that I don't loose vacuum), conventional cut. Using the three pass method, I get excellent sizing, almost excellent edge (still needs light sanding) and excellent cutter life. Even with MDF and particle board, I make two passes. The climb cut is -0.65 and the conventional cut is at -0.725 (assuming 0.75" thick material). Dimensional accuracy is excellent when I use a climb cut followed by a conventional cut.

At slower feed speeds, I use a 1-flute cutter. At higher feed speeds, I use a 2-flute cutter. All my profile cuts in sheet goods are made with a spiral cutter.

The limitation of my machine is the vacuum hold-down. The 3hp spindle will cut one-pass, but the parts move too much, even with two FEIN vacuums (4,500 ft altitude kills the suction). For full time heavy production, I would use a larger spindle. The 3hp can do the job, but I don't like to push any tool at its full load rating. The built-in amp meter on the Delta VDF makes it easy to monitor the current being drawn by the spindle. In plywood with a 3/8-inch cutter, it's easy to approach 3hp when cutting 1-pass.

The only experience I've had with the Oriental Motor PK296 size motors has been on my test bench; however, the PK296B2A-SG3.6 motors that I test have excellent torque and speed when run wired half-coil with a 30VDC power supply and the Gecko G203v stepper driver. I don't know exactly which motor Shopbot is shipping with its standard machine or how they have configured the machine, but if I were buying a 2nd machine, I would go with the PRS-Standard and then tinker with the electronics - if necessary. (However, I spend more time tinkering with electronics than I do cutting, so my situation may be much different than yours.)

[Gary Campbell]

Sebastien...
I will be adding it to the same machine. That gives us 2 spindles and 2 drills. We feel that combination will give us the ability to process virtually all of our panels without a bit change. I have posted a couple pics (without the 2.2 in place) here: http://www.talkshopbot.com/forum/messages/28/34979.html?1225580290

Since I havnt used one, I cant give an opinion on the 2.2. But as Mike says above, if you use smaller cutters and even single flute cutters, you can tweak just about any machine to cut just about anything. You will very seldom sacrifice cut quality, just speed. As Mike says above... it takes horsepower to push a 3/8 bit thru plywood. If you move them slower they heat up and bit life is shortened. To increase chipload decrease number of flutes. That will allow longer bit life at slower move speeds.
Gary

[sebastien1]

Mike, Thanks for the cutter and number of passes insight. I'm learning a lot. Thank you.

Gary, I see the benefit adding this the same machine, which I didn't know could be done. My question now is; do you have special software to operate 4 tools on the same machine. Are you using something other than "PartsWorksPro"? Thanks.

[Gary Campbell]

Sebastien...
PartsWorks comes with postprocessors for dual cutting heads, up to 4 drills and an indexer. Software is all there, you just need to buy the accessories to meet your needs.

To get full use of 2 heads or more than 2 drills you need to get the 60" wide version as I have. This allows full coverage of a 4 by 8 sheet with all 6 tools.
Gary

[david_white]

Sebastien
I struggled with the same question about what to buy and went with the 4x8 with the 4 hp hsd spindle. We cut mostly solid wood round parts for the Mikron moulder . Most of our time is in the glue up of the blank ,so the speed of the router was not all that important we cut all our parts in 3 passes , and are very happy with the machine . If you are losing steps you are doing some thing wrong like a dull bit or just pushing to fast and when this does happen it is obvious buy the noise it makes. But i would agree that you would want to have an air drill if you are going to cut cabinet parts . just to give you an idea as to how fast you can cut parts out I cut a sheet of 3/4 oak ply wood (H.D finest) yesterday for a cabinet . This is what I cut.
6, 9.5 x 28
6, 9.5 x 27.5
2, 18 x 27.5
1, 15x 7.5
All cut out of one sheet of ply wood with a 5/16 bit. Also had a bit change to dado out for 1/4 ply wood for the drawer bottoms. 19 min. all parts are square no tare out and i only had to handle the sheet once. The best part about having the machine cut the parts out is that in that 19min i was doing another task.
Good Luck.
Dave

[wberminio]

Sebastien

I made my decision on PRS Standard last year based on Space/Price.I decided on 96x48 machine with a 4HP HSD Spindle,16.9HP regenerative vacuum,air drill and upgraded my KCDw software to their ONE-BUTTON.
I build custom cabinets, for the most part.After less then a year of use,I can say I'm very happy with the results.
The vacuum is great.I put down a full sheet of plwood and there is no movement, without any tabbing or onion skins(which is a pain and can hold up production)Plus, a valve on the exhaust is providing extra heat this time of year.The spindle is a definite plus.A far as losing steps,As soon as I tweaked the feed rate,this is all but elimated.The drill has eliminated an extra step and material handling. The only thing I would have changed is possibly making room and getting a 96x60 for a future 2nd Z, as Gary suggests.
As a small,presently one man shop,I can just about keep up with "Luigi".I still have the option to upgrade to an Alpha and even add 60",If necessary,in the future.

Erminio

[sebastien1]

Dave, thanks for the info. That seems pretty fast to me. Did you buy the "standard"? Is the 5/16" bit upcut, downcut, what works for you? What are using for hold-down?

[david_white]

I have A standard the bit is a down cut .I bought a 7.5 hp regenerative blower on eBay for 350.00 it works great. I think in order to pull the sheet goods flat you need some type of vacuum. just putting screws in the corners will cause the middle to bow. I don't know ware you are located but if you want to stop by for a demo let me know.I am in N.J

[sebastien1]

The vacuum will have to wait. What is the best mothod for non-vacuum hold-down? Doesn't a down-ward spiral bit help push the ply down?

[rcnewcomb]

If you aleady have a shop vac you can give vacuum a try. Just drill a hole in your table the same size as your shop vac nozzle and hook it up. Use some 1/16" gasket material from All Star and you will be astounded at the holding power even from a super cheap shop vac. We ran with this configuration for years before we went something more advanced.

7909

[sebastien1]

I'm going to be cutting 4x8 sheets of 3/4" ply. This set-up seems a little too small for that; it is not? Also, wouldn't a regular shop vac over heat? Thanks

[harryball]

Shop vacs are prone to overheating but many survive and do just fine. I have one that I used about a year before making the jump to twin Fein Turbo III vacs, which was worth it. One way to help make sure your shop vac does not over heat is to give it a little air so it is never completely sealed off. You sacrafice a little bit of vac but you can reach an acceptable balance.

The Turbo III's do not rely solely on airflow through the vac for cooling. I've run mine continuous for 8 or more hours. Some guys on the forum have run them longer. You can run on one vac and do well until you can afford the second.

/RB

[sebastien1]

Thanks, RB and all those contributing to my quest for shopbot knowledge... Well this certainly seems like good news! Wouldn't I need at least a couple shop vac's to hold a 4x8 sheet down? What all the lost suction when you start cutting through the sheet. What about using a dust collector for this purpose?

[david_white]

A dust collector will not have enough pressure. If you use a down cut bit the saw dust is impacted into the cut. This does two things helps with the loss and keeps the parts from shifting. A common shop vac has quite a bit of holding power.

[woodworx]

Nope dust collectors won't work for a vac table. The suction works on a different principal. The more duress the turbo III's have, the more suction they generate. Put your had over the the tube and you will hear the motors pumping harder. Dust collectors will loose suction power if you clog them. Get 2 right away. You will like them when you have the extra power. Get a third to clean up the rest of the shop, or use that dust collector you spoke of.

[Gary Campbell]

Sebastien...
Most dust collectors have high cfm (650-2500) but only around 10 to 15 "H2O. This is around 1"Hg (mercury) of vacuum. It takes a minimum of 5"Hg to hold parts. The Feins will have just under 7"Hg and around 100 cfm. Thats why they work.
Gary

[bcondon]

At the Shopbot Camps, there were discussions about having small vacuum pumps (typically 1/4HP, 3.5 Cfm but will pull 20" HG) for around $60. Coupled with a 10 Gal portable air tank for reservoir, what is the opinion of such a system?

For around $100, we can at least get started. These pumps are very quiet (unlike the Fein)

I am looking at smaller objects with self made vacuum pucks (they sell them for $20 each but can make them for $2.25 in bulk)

Surfacing table for the first time over the weekend... everything else is operational.
Thanks

[david_white]

Bob
The small pumps work great for small parts or even big parts however you must be very careful not to break the seal of the vacuum by cutting through the part that is on top of the puck.I built my system from the parts on Joe wood-worker.com . as for the reservoir 4 inch pvc pipe works good . I bought the pump from Nebraska wholesalers .

Dave