Low Volume Vac. Work-holding

[glenninvb]

Although a complete newbie here,
Inspired by rscrawford's outstanding vacuum jigs, I thought I would start a thread on low vol. vac. work-holding and see where it goes.

With my long but limited machine shop experience, work holding can be the trickiest part of any job whether running a tooling center or just a homebuilt CNC router.
Especially those of us that don't have a three phase 20hp high volume vacuum system sucking through a spoil-board.

Even though I posted pic's before of my simple 20x20"x1" vac. grid before, its made from 1" King starboard. For anyone that does a lot of acrylic engraving it becomes very handy. the edge of material is always square to machine axis, just flip a switch and machine away. Its nice to engrave perfectly flat material without having to surface spoil board or table top.

Also once you have the main plenum or table (any size) you can fab jigs that sit on top from sealed MDF or Starboard and by using soft rubber cording like I use or flat gasket rubber, almost any part with flats can be positioned with repeatability.

For example I used a throwaway MDF jig that sat on top my plenum for inlaying multiple types of wood in clock faces and then to be able to put back and engrave at a later time. As it had no square edges the jig was handy.

The jigs need a way of being registered for placement whether pins, grids, guide strips or whatever, and of course the Starboard plenum and jigs can be machined flat when making or trued up when needed.

The only drawback to low volume vacuum is the part must make a fairly good seal to plenum or jig.

Here is a link for cut to size King starboard
http://www.boatoutfitters.com/cut-to-si ... -starboard

McMaster Carr
for round or flat gasket material

Very nice tables (I bought a very small one)
http://www.clampusystems.com/RAL-V.html

I found the new Gast Vacuum pump on EBAY for 100.00
Also a couple snips for very simple sit on top jigs for pocketing or profile

[sawmiller]

Do you have a link to the gasket material?

[rscrawford]

That's a pretty sweet set-up. With the vacuum grid and the different pallets that index to it, you can change jigs in a matter of seconds and be perfectly indexed each time!

[dgoddard]

Which model Gast vacuum pump are you using?

[glenninvb]

rscrawford,
It's nothing like your rig, but same principle and inexpensive, Your table is as good as it gets, I think I made a good decision when installing 3/4" phenolic with a helicoil grid pattern on top of my aluminum table. I believe I noted you also installed T-slot track in yours as well?

Sawmiller,
I ordered a couple, I think I'm using the EPDM, it needs to be soft or the grooves would have to be machined deeper, I machined mine 1/8"x .080 deep and use 1/8"dia, round foam cord. As long as the seal compresses to allow part to make 100% contact to table it works, especially important with thin flexible materials.
I may be using the softer Santoprene ? I'll check

http://www.mcmaster.com/#standard-rubber-cords/=r6vmky

dgoddard,
It is the same small gast pump on the other link I provided, ROA-P201 I think they list for 370.ish, got lucky and found one brand new for 100 on EBAY, there is usually a lot on there.
I installed extra cooling fan on the one I bought, they get hot after several hours, also a needle valve to keep pump from working so hard. On large parts 20"Hg is more than enough and the pump pulls down to about 25"
If you have compressed air supply the vacuum generators are another way to go

[stankern]

That pump you spoke of does an excellent job jere is my story

part 1 building a vac press part 1

part2 building a vac press

building the vac press part3
Then a puck was also designed and works well