Using Labratory Vacuum Pump For Clamping

[kerrazy]

I just picked up a precision belt drive vacuum pump and am curious if anyone else has used a similar style pump for vacuum clamping pieces.
Any suggestions ideas would be greatly appreciated.
Dale
precision Belt drive pump (http://www.precisionsci.com/lab/products/vp_belt.htm)

[rgbrown@itexas.net]

Dale,

You will find all wood and wood products to be very porous. In my use of similar pumps, I found I never could stop enough "Leaks" to get it to properly hold with the small volume of the pump. For holding plastic parts - Acrylic, UHMW and Poycarbonate, it worked fine. I had to always use a gasket and something better than wood for the substrate. The low volume of mine, it was a 1 1/2 HP unit, would not tolerate any leaks.

Low volume pumps will also not "pull down" large sheets like a high volume vacuum system will. However, if you have enough volume, it will hold a lot smaller parts. Depending on barometric pressure, pumps of that type can develop over 2100 pounds of holding force per square foot. This kind of pressure can also distort holding fixtures and the part being held.

Good Luck,

Ron

[jay]

Dale, a little while ago I picked up a Welch Duoseal 1400 Vacuum pump. Welch Vacuum Pumps (http://www.welchvacuum.com/pdf/vacuumpumps.pdf) (PDF file) It is small, only moves 25L/min. I made a small vacuum board to hold the size of wood you use for your small residential signs out of MDF. Put 3 coats of varathane and some good old Canadian Tire closed cell weather stripping around the edge. Works great. I put a couple of dowels in the bottom so it is positioned exactly in the same place everytime I put it on the table. I have just aquired another Much bigger pump model 1397 with 500L/min. capasity and am looking forward to rebuilding it and using it for the full table in four zones.

Prior to sealing the vacuum board with varathane it did not work worth a dam.

[sheldon@dingwallguitars.com]

We use 4 styles of vacuum. Shopvac for sheets that will have a lot of holes in them. Ventury for portability, Gast rotary (dry) for medium/low volume and an oil filled rotary vein lab style for ultimate hold on small parts.

I agree with everything said above. The only thing I can add is that for low volume/high vacuum situations, you also need a way of distributing the vacuum to the entire gasketed area under the work piece.

100 grit stickit strips work very well. It allows airflow under the part and helps keep it from shifting. You can also mill a grid inside the gasket area with a V-bit, but that's more of a PIA.

[garyn]

Dale,
Have you seen Bill Imschwiller's vacu-puck system he designed? Check out the pics from Bill P's camp and you will see he uses a pump similar to what you are talking about. He can even add more than one puck for additional pieces or a longer piece. He uses the "D" shaped gasket mat'l on the top and bottom of the pucks to hold the pucks to the table and the mat'l to the pucks. It is pretty neat system.