[MidFloridaTech]

Hi, I am a student at Mid Florida Tech and I was thinking about creating a Vacuum Table to sue for engraving and machining. This would go on the school's Hurco VM1 and be machined on it mostly as well. My plan was to use ~150 10-32 set screws in rows and a 1/8NPT inlet for vacuum as well as one for a gauge with the under surface "tubes" being drilled 1/4". The table would have about 12"x10" of holding area.

How can I use the shop air to create the vacuum?
How many psi of vacuum are usually used to hold parts in place?
I have seen others which operate off of shop air but do not know how this works. If I need to attach an external vacuum source that runs off electrical power and not shop air, what is commonly used?

Any advice for construction or perhaps letting me know how well these work?

My plan was to use 1" Mild Steel plate for material so that it could be ground flat on a surface grinder.

[tnik]

you would need some type of vacuum pump to get a suction. depending on the material you might be able to just use a shop vac motor/pump, but with one of those you really have to watch out for heat buildup because it wont take too much.

we made a couple here out of aluminium and on plastic parts it works like a charm. but we did buy a commercial vacuum pump.

the amount of PSI you would need (not sure if a vacuum is gaged in PSI) would depend on the material and how flat it actually is I would imagine.

other than that, the setup you described sounds to be fine.


edit:
For the fun of it, I google searched DIY vacuum tables and came up with a crap load of resources.. might want to do that too..

[MidFloridaTech]

I did but most of the ones I saw were about vacuum forming plastic. I want something to hold a piece or jig for machining and quicker parts changes.

[tnik]

yea, thats what I figured you wanted.. and it all depends on the material and how much suction you actually need. But I don't know of any way to use shop air.. you would need a vacuum motor, like from an old vaccum or shop vac.

[lgalla]

Vacuum venturi operates off shop air.
http://www.2linc.com/venturi_vacuum.htm
Larry

[VWSatOz]

You can use a vacuum generator from Festo or the like, shop air pressure &venturi creates partial vacuum, you might get 10 psi atmospheric thrust. If your parts are only 3square inches area you only get 30lbs thrust, friction might be 10% of that so you only get 3lbs.force of side thrust off your cutter before this small job slips. Bigger area workpiece gives obvious improvement, & you need edge & end locating stops for reference & to take all of the side forces you can, especially if you program your cuts so the forces push towards these solid stops. If you are milling thin stuff then its a great way to hold it down flat, if you can combine solid side-locations say cams in your screw holes then it becomes a more secure nest to rigidly hold your work without the buckling effect of vise clamping.

[ctate2000]

You can buy a vacuum generator from Mc Master Carr. It runs on shop air. If
I remember correctly it will set you back about $100. Look at Vacu-Vise for design ideas. I have owned their large chuck and it works very well. Plenty of hold down for a large part. A poor mans version of the vaccum chuck is to use common super glue. Super glue works great if you stay away from the synthetic coolants. Glue the part down, machine it, then disolve the glue with acetone. I have done this with small parts for milling and surface grinding.

[neilw20]

This is a tidy and reliable vacuum installation.

http://www.cnczone.com/forums/showthread.php?t=34537

Well done Greg.

[ImanCarrot]

One thing: have an adjustable valve with a vacuum gague, I find it invaluable to have a low vacuum when setting up, tapping the part into posiiton/ square/ true then whack the vacuum up full to hold it