Need Help!- Old Vacuum Cleaner

[Drakkn]

I have an old vacuum cleaner and would like to build a vacuum bed for my cnc machine ,anyone done this before and have any comments good bad indifferent on the subject.Have read lots of posts and got a little confused as always building on a low budget.

[One of Many]

Originally Posted by Drakkn I have an old vacuum cleaner and would like to build a vacuum bed for my cnc machine ,anyone done this before and have any comments good bad indifferent on the subject.Have read lots of posts and got a little confused as always building on a low budget.

You would be best served finding a used Gast rotary vane vacuum pump and some kind of tank plenumn to get nearer to 29-30Hg of pull on your surface. I'd wonder if any vacuum cleaner motor will get near half that before it unloads with no flow and sustained pull to hold the work piece solid. The other issue is that those motors need good flow for cooling to survive.

You may get away with with it if you create a slightly leaky nest with side shift supports rather than a sealed flat surface. At least do some tests to see how well or where the vacuum unloads and the motor RPM's jump before you trust it.

If 30Hg is equal to 15psi, then based on your actual Hg, you can calculate how may square inches and what force is holding it down verses the cutter loads trying to push or lift it off the bed. There isn't much warning if any, with the exception of the operator keeping a close eye on a vacuum gauge connected to the vacuum chuck\bed.

DC

[Geof]

A vacuum cleaner simply does not have enough suck.

You need to be able to pull a negative pressure of at least 20 inches of mercury which is about two thirds of an atmosphere. This gives you a differential pressure of 10 psi so the force holding each square foot of material is about 1400lbs.

To get this kind of suck you need a proper vacuum pump, or you can do as I did:

http://www.cnczone.com/forums/showthread.php?t=53796