What to buy

[T.McCaw (Unregistered Guest)]

High every one . Tom here.We are about to replace our floor model panel saw which we use to cut plexi glass with a vertical panel saw. The recovered floor space will be for a cnc. I have been a TurboCad user since V6, now running V10.5. The thing I like most about TurboCad is their forum. Dignified responses to all no matter what the question is. So what does this have to do with any thing. I think we will purchase the ShopBot. Forums are the life line when help is required.
So what should a plastic shop order in bells and wistles when they buy the ShopBot? At first glance a vacuum table seems to be a place to spend money. And perhaps the Porter Cable is not the way to go. What should I know or what questions should ask or be asking ourselves when we place the order. Any help from some plastic shops will put you to thr top of my Christmas list (mind you its now 361 days away and my mind isn't what it use to be' and they say its your legs are the first thing to go)

Tom

[richards]

Hi Tom,

Congratulations on deciding on Shopbot. For the money, I can't imagine any other tool coming close to it's performance and specs.

My experience with plastic is very limited, others will give you good advice on specifics; however, I would recommend a spindle instead of the PC router. I still use the PC - and it works reasonably well in MDF and plywood, but when I tried to cut plastics, I had a lot of heat related problems. Since the PC only has five speeds, and since those five speeds vary greatly depending on the load to the motor, finding the right feed speed and the right rpm was frustrating. The spindle with its greater hp and totally adjustable speed control would give you more flexabilty.

A good vacuum is a must (as far as I'm concerned). Depending on the size of the parts your cutting, you might need a GAST vacuum pump (or equivilent) and gasketing materials. When I cut plastics, the GAST pump works best for me (very small parts, slick material, etc.)

In any case, good luck. Spend some time browsing the forum. There's lots of good material already posted that will answer many of your questions.

- Mike

[cnc_works]

There is no doubt that, given the choice and the budget, I would have a spindle.

That being said, just my recent, moderately limited experience in cutting acrylic plastic has shown me that I can be pretty productive with a PC890 router. I have cut several 4' X 8' X 3/8" sheets of parts with an Onsrud 0 flute 1/4" upcut spiral bit specifically designed for plastic. Details cut with a 1/8" similar bit.

One pass with the 1/4" bit at 80ips, 20K rpm sometimes with a .03" clean-up cut if I want to try for the best surface, though I'm not yet convinced that it is noticeably better than no clean-up cut. Definitely not as good a surface cut as my smaller, heavy duty CNC, but certainly acceptable to my customer.

The cut produces fine shavings, sometimes not clearing and packing a little into the cut path, but I don't have any problems yet with heat or melting.

I have had problems cutting some acrylic plastics, extruded I think, that melted onto the bit and was a major PITA.

Because of the variety and mixed sizes of the parts, vacuum just doesn't seem like the answer, so I have been using tabs with a clamp system and the occasional screw in the middle.

And, by the way, I'm definitely open to suggestions to improve my current methods.

Donn

[fleinbach]

Donn,

I believe you ment 80 ipm didn't you?

[cnc_works]

Oops, wasn't supposed to let that cat out of the bag. ShopBot gave me a new beta Zeta model to try out. The wind of it going by will practically knock you down. The inertia of the head changing directions makes my shop slide a couple of inches. I have to keep a Cool air device on the tracks just to keep them from melting down.

Yup.

Donn

[elcruisr]

Hi Tom,
we routinely handle sheet plastics in our shop. Mostly acryllic and polycarbonate wth some expanded PVC thrown in for good measure. You'll need the power and RPM control of a spindle for sure. Go for a big pump and a vacuum table. The smaller your potential parts the bigger the pump! We have a 15 hp FPZ blower. It's adequite for most work but my wish list includes a Becker or a Dekker pump system. In my wildest dreams it would be a 40 hp Travaini. No tabbing needed with that beast! You'll want the proximity switches and zeroing plate.

In software you'll want a package that gives you alot of control of your toolpath generation. Make sure it will be easy to do finish passes, final thickness passes, and control generation and placement of tabbing and do it fast! Don't just concentrate on drawing, that's only half of the job.

Don't forget the tooling issue. Start researching plastics tooling. There isn't one tool for everything. Plastics tooling can get pretty fussy. When I call up my tech rep he wants to know not just that it's acryllic (for instance) but is it cast or extruded, made by who and do I have their exact product number? The more info I give him he has refernces for the exact tool for various edge qualities and the best feed and speed information. You might want to look at the Van Niser articles on the Onsrud website. There's tons of good info there on machine cutting plastics.

Good luck!
Eric

[ron brown]

Tom,

I too will state I would get a spindle and a good vacuum system. I prefer large volume vacuum systems with as many CFM as you care to afford. As Eric stated, a lot of what you need to learn is in tooling.

Donn,

Yours must be an early prototype. The one with Liquid Nitrogen cooling uses the vapor boil for the vacuum table then bit cooling.

Ron

[mikejohn]

If you have read this Gerald, why are we being denied a high speed metric machine?
If 80ips is good enough for the Americans, then 2032 mm per sec seems good enough for us.
............Mike

[fleinbach]

40 HP Travaini

Watch out Eric As soon as you cut through the material it'll probably suck the Z axis right down to the table.

[elcruisr]

I want a pump so powerful that if my helper isn't careful it'll suck him onto the table and give him a big hickee!!!

But seriously you run into alot of warped plywood these days and when turning them into nests of little parts (even with tabbing) there's no such thing as too much vacuum!!

Eric

[T. McCaw (Unregistered Guest)]

Thanks guys keep it coming. Vacuume stong enough to suck z axis.spindle with hyper drive.
Question... If holding down small parts is an issue would it be better to have a smaller table then lets say a 4 x 8.

Tom

[richards]

Tom

Get the biggest table that you need and use a zone system to more easily regulate the vacuum to smaller portions of the table (shopbot supplies a 4-zone file with their software).

If I understand vacuum properly, it's the pressure of the atmosphere that creates the hold-down (somewhere around 12-14 lbs per square inch). The vacuum pump simply removes air (suction) to let the atmosphere press down on the part. A big vacuum pump will keep that suction even though some air is slipping around the part (hence the listing of CFM in the vacuum's specifications). A very small pump, 1/2 or 3/4 hp, can hold just as well as a very large pump if you use a vacuum mask and the proper gasketing to prevent air from slipping around the part. Since it is the atmosphere that is holding the part down, if you use a small pump or a large pump to generate the 25+ inches of mercury, the hold-down pressure is the same. Of course a large pump will suck the part down quicker and allow you to cut without resorting to a vacuum mask, in many cases.

If I had my choice, I would use a big vacuum and forget about a vacuum mask, but I work with what I have and hope to buy what I want as time goes by.

Now, back to the table size issue. Most of my work could probably be cut on a 24x48 inch table, but that means that I would have to cut all panels to rough size before sliding the material onto the table. My Alpha is the 120-60 model so that I can easily cut 48x96 material as well as 60x60 baltic birch ply. The extra 24 inches on the x-axis has proven to be real handy as a 'landing zone' for the y-carriage. By using the 'landing zone', I have full access to the entire table top when I change sheets of material.

[T.McCaw (Unregistered Guest)]

Thanks Mike. A vacuum mask would not work here. Runs are small and always different. We too could probably route everything on a 4 x4. At the moment we have a 12' panel saw ... cut lage sheets down...even recut on tablesaw. route by table mounted routers and jigs. We get some of our jigs cut by laser up the road and some parts if need be.

Tom

[ron brown]

The thought of vacuum and vacuum leaks needs to be addressed. If one had "Super-Scuker 2010" vacuum pump, comming into existance about the time a practical tele-transporter comes in effect, the same hold-down problems will exist. The "air slipping around the part" will cause the parts not to be held down properly. Small parts will loose at least 1/2 the thickness of the spoilboard around the perimeter area when they are cut through. It could be less if thin bits were being used.

A true "pin-hole" causes a 28" 4 CFM vacuum pump to go to about 15" of vacuum. This was measured at the pump. In the areas around the pinhole the vacuum was noticably less than that.

I commend Mike on chosing the larger table. On my first ShopBot controlled machines, I had a 4' wide "Y". I cursed it every time I had to cut a sheet of 5' X 5' plywood to fit the machine. I had a 62" Y axis on my last one. I'll build the next one out to at least 64". If I have room, I'll have 16' or more of "X". I'd like to use 24' material for the table and have a 22+' X.

But, if money were no object... and I didn't have to make a living, life would be a bit different.

Ron

[superior]

I once heard the search for a good vacuum system was like the search for the "Holy Grail", and as time slips by, that holds forth more and more.
I have two pals that own/use multicam equipment, one a 4'x10', the other a 5' x 10', both costing well over $65,000. Now the the gist of this post: I have seen/used both systems several times. Both systems have the approved/furnished HUGE vac systems. Both run on 240 volt hookup, etc. Just for funnies, I have cut 4" x 4" pices of plex, aluminum and masonite. These were placed on the table (MDF) and the vac turned on. None of the pieces moved so much as a hair...I cut numbers, letters, and geometric shapes onto and THROUGH them. Again, no movement what so ever. Multicam lists their vac systems at about $5500.00, as I recall. After the trials and tribulations of trying to cut some small stuff for Christmas ornaments, I think that is a bargain.
I am no engineer, probably can't spell it correctly. I just wanted to pass this along to all my bot' buddies for what it is worth. I currently use a five zone table, with both a Sears shop vac and a dust collection system. Still can't hold small stuff down.
I feel as though I am in about the same position as most other botters on this issue.
Looking forward to your feed-back.
Doug

[T.McCaw (Unregistered Guest)]

On a visit to a shop I worked in a long time ago they had purchased a cnc machine and I got to see in in action .They would mask the bottom of a sheet of styrofoam (they actual had a machine that would mask a 4 x 8 panel all in one shot.Kind of like a paint roller machine)on to the bed the styrofaom went. The router did not cut through the tape. The operator would slide the cut sheet out of the way, put another sheet on and then pick apart and bag up the words required for the deli section the produce section and so on. I bet you this machine paid for itself in no time. It was fast and quiet. What make no idea.

Tom