Very Flat Vacuum Clamp

[analogman]

Hey all. I am engraving faceplates for electronics equipment. They are 3x20" on .040" material. The engraving depth is quite critical .001" tolerance.

My machine is very rigid and can do the .001" repeatability no problem, but I am having problems keeping the material flat. I have been using double sided tape, but it is not keeping the material flat enough.

So I ordered a small vacuum pump and want to construct a vacuum clamp that will keep thin material flat to .001" I asked JoeWoodworker, but he did not have any suggestions.

Any suggestions from the crowd?

thanks

[rlwoodjr]

I wonder if a granite inspection table with holes drilled in it would work. I think you can buy these in different sizes.

[Geof]

Are all the faceplates the same size?

If the answer is yes simply make a vacuum base out of aluminum; actually two pieces of aluminum.

Machine a labyrinth in the two pieces and fasten them together. Tap a hole for the vacuum line so it intersects the labyrinth.

Bolt the two plates securely on the machine table and machine a shallow pocket to take your faceplates.

Around the perimeter of the pocket mill a small groove to take a length of soft O-ring cord.

Drill many holes in the pocket to intersect the labyrinth between the two plates.

Put your faceplates in the pocket and apply vacuum; they are going to be held as accurately level as you machined the bottom of the pocket.

[analogman]

That sounds like it will work Geof - thanks!

[bsdphk]

That sounds like it will work Geof - thanks!

You may be able to use the same trick I use for pcb's, probe the height and let the G-code interpolate the correct Z:

http://phk.freebsd.dk/CncPcb/

Poul-Henning