I Don't Understand the Need For a Vacuum Table...

[tuck]

With all due respect for those BotHeads currently using a vacuum table set-up, I'm sure you have your reasons, but after reading through these forums about all of the different vacuum set-ups and what works and what doesn't left me wondering what I could be missing. My conclusion is that I'm not missing anything but a lot of expense and trouble.

I've been a successful BotHead for about 4 years now in the sign business. I've cut a lot of different materials in all sizes and thicknesses and haven't done a job yet where I couldn't just screw my material down and cut it. If doing cut-out letters, for instance 1/2" thick PVC, I use a spiral-down bit. This packs the chips into the kerf and holds everything in place. If cutting out very small pieces out of thin material, say .040 aluminum or .125 acrylic, I may cut with small tabs (bridges), then finish the cut outs with my jig saw with the sheet laying on some thick styrofoam...no problem.

The only thing about screwing material down is to be careful and not put a screw in a tool path. That has happened only once to me in 4 years.

So,...someone clue me in. What am I missing with a vacuum set-up?

[Ryan Patterson]

Mark
I vacuum would not be for everyone. I vacuum works great for me cutting cabinet parts. Screwing the parts down would not work because there may not be any unused sheet left. Speed ,I do not need to remove any clamp or screws. I also do not need to plan my cuts around screws. When I first got my Bot 4 years ago I did not have a vacuum and found more advantages using a one.
Ryan

[tuck]

I hear ya, Ryan, but don't you start losing vacuum when you're cutting all the way through? Also, I recently cut out some small (3") letters out of .250" ABS plastic (it's some tuff stuff), and I'm quite sure it would have taken a vacuum table with enough power to suck a basketball through a garden hose to hold down the small letters in place for the final cut. I programed a few small tabs on each letter and had perfect results, no problems.

[matt_p]

guys,
as a botter who went w/o a vac table for 3 years of cutting, just screwing and clamping, I have to say that the advantages of a vac system pay for themselves in convenience and speed. I agree with Ryan, time is money.
My set-up is a 7 zone on a 5x10 table with a fein turbo III and it is 90% sufficient for what I need. but that said, I still use clamps on the edge on most sheet goods. The beauty of a bot is that you have all of these options!
Plus when you run that new $40 long spiral bit into a screw, you realize that there has got to be better way.

[tuck]

Matt, you say "7 zone". If you need only 1 or 2 of those 7 zones, don't you have to mask off the other zones to not lose vacuum power? And if that's the case, isn't that a huge hassle? Pardon my ignorance as I obviously don't understand the ins and outs of a vacuum hold-down system. It's just strikes me as amazing that I have managed to do so well for so long without one.

[mikejohn]

Mark
I am also non-vac
Most of my work is limited to cutting solid wood boards, which are never perfectly flat, and a particular V-carve sign for which I have simple jigs.
By cutting one side of the table, I can safely remove material from the other, and the bot just cuts all day without stopping.
Material can not move in x or y, it has edge stops, and simple edge clamping keeps it flat.
Clamps are drawn in on the original drawings, and avoided when making the cutting files.


Theres no vac noise, no power costs, no danger of vacuum failure causing ruined material or broken $40 bits.
For me, it works fine, for others vacuum seems to be the hold down of choice.
Horses for courses, as they say.

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

Gerald, come on in, the waters lovely

[tuck]

Thanks, Mike. I agree with "horses for courses". A horse is a horse is a horse, of course! :-)

I'd like someone to post why a vacuum table is an absolute necessity for their work on CNC and how it justifies the expense/noise/trouble vs.screws/tabs/clamps/edge stops. To me, all it takes is a little bit of thought on how and where to fasten the material to the table and/or where to program tabs if necessary.

[gerald_d]

*splash*

Also a non-vac guy here. The only time I look in that direction is for holding huge boards down firmly while aggresively cutting them with economical up-cut spiral bits. If we could get economical down-cut spirals here in Cape Town, it will be a different situation.

But, we do have a crude sucking system on the Bot table, connected to a "shopvac" for holding warped marine ply down tight while cutting controlled depth steps in them - the only other way to hold them down would be with a pressure foot on the router/spindle.

[Ryan Patterson]

Mark,
Yes vacuum is lost when cutting through but the blower (15hp regenerative blower) is big enough to recover. I am able to cut up to 70 sheets in a day 8 to 9 sheets an hour. If I used screws I think it would take at least two minutes to go around and unscrew the cut parts and screw down a new sheet. I charge $25.00 per cut sheet so, by screwing/clamping I would lose 140 minutes in a day or $464.00 in a day. In what I do, a vacuum would pay for it's self fairly quick.
Ryan

[sawkerf]

All you have to do Mark, is to cut out a set of cabinets with about 25 sheets of plywood with system holes and another 5 sheets of drawer box parts, all the while trying to keep up with a contractor. I'm sure then no one would have to convince you of the need for a vacuum. It all boils downt to your individual need. Kip

[tuck]

Ok, I've been enlightened by Ryan and Kip. I suppose a high daily production of mulitple sheets of material could and would necissiate the need for a vacuum table. My type of business is different and I'm GLAD! I don't want to work that hard! ;-)

Cheers, and thanks for your input.

[mziegler]

Hi guys,
I am also non-vac botter. (mine table is plumbed for vacuum but have not use it for awhile)
Vacuum is great for production run of hundreds - thousands of parts and I would use vacuum if I have the orders. Right now only production runs I have is for is cutout numbers and letters and simply nailing the parts to the spoil board work OK. Holding small parts like numbers and letters by vacuum is difficult and usually means using a dedicated vacuum fixture.

Most of the time I nailed the parts with brads, plastic nails or pins. All depends on the material and the thickness of it. One neat trick I have done couple times is to do a stack rout. Nailing 2, 3 or more sheets down together and than routed thru all sheets at once. All depends on the thickness of the sheets and your cutter size and length.

Also I can better use the full length of the cutter by nailing a temporary spoil board on top the regular spoil board and than cutting on the top half of the bit for thru cuts and using the bottom half for pocket cuts. If parts has only thru cuts, than lower the cutter as it get dull to use full length of the bit. The cutter last longer also because the sawdust has someplace to go to and thus the bit generated less heat. Guys that has vacuum pod systems do this too.

It’s all about making the best of what you have. Mark