Material between my Vacuum Table and Part other than O-Ring

Anyone have any experience with placing a sheet of something between your part and vacuum table to allow you to machine thru the part completely and not machine my vacuum fixture? I recall seeing some sacrificial material that allowed vacuum to "go thru" it but a search has turned up nothing. Or does anyone have any other tips or tricks?

MDF maybe?

Light weight MDF is often used with CNC routers. May not remain light weight with coolant. It works with CNC routers because they use massive rotary vane or liquid ring pumps.10, 25, 50 HP.

No experience with it IBAG Vac mat. So far I have either made custom fixtures with O-rings or cut up sheet rubber to use on a flat vac table, which requires at least a 1/3hp rotary vane pump and larger part IME.

You can make a base plate that mounts to your vacuum table out of aluminum with holes in it for the vacuum to pass through. Mill an oring groove into it that matches your part profile then you can mill a tad deep and into your base plate. Pierson workholding has a bunch of online videos showing this technique.

I've used MDF a fair amount, but it was mostly for woods and plastics. Works well for those materials. Normally when I don't want to machine into the vacuum plate I'll leave a .005"/.01" foil where I'm cutting and pop it out.

Pete Deal said:

You can make a base plate that mounts to your vacuum table out of aluminum with holes in it for the vacuum to pass through. Mill an oring groove into it that matches your part profile then you can mill a tad deep and into your base plate. Pierson workholding has a bunch of online videos showing this technique.

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That's what we have, and do. But sometimes the situation isn't ideal so we have had to make our own custom vacuum "table" that is part specific. It's not even a table really just a port for the air, and a pad for the part to sit on.
Maybe that's something the OP can do?

I saw this in use at Eastech last year MultiCam Tooling | Foam Sacrifice Mat | Vacu-Mat it was on a big ass router table though.

mcclij01 said:

Anyone have any experience with placing a sheet of something between your part and vacuum table to allow you to machine thru the part completely and not machine my vacuum fixture? I recall seeing some sacrificial material that allowed vacuum to "go thru" it but a search has turned up nothing. Or does anyone have any other tips or tricks?

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There are a few ways to do it, but it has alot to do with the type and size of part your running, Ive used 1/16 1/32 sheet plastic and drill a ton of holes in them. problem with this is you look holding power and your parts tend to slip more. In my opion its faster and cheaper to make a plate for each job you get. Making a vaccum plate isnt hard nor is it time consuming.
keep in mind Plastic is not somethign you want to use for a fixture unless you have a huge amount of surface area and are primarily drilling as it makes parts slip extreamly easy.

if your only making a few parts cut them down to .005 then tear them off. and do a second operation to clean them up. in the long run its faster than having to fiddle fk around with parts sliding and and making a subplate so to speak. we do that cutting 40-50 small parts off a sheet. then do a 30 second to 1 min second op. Parts look better also.
Again it all depends on your part.

I have 3 or 4 generic so to speak vaccum plates they are the size of the mill table 40x20 to 12"x24" even have a plastic on 2 inchs thish that is 60" inchs x 24" that we use on our 40x20 fadal to support over hang. I have about 50-75 vaccum fixtures for each part also. I prefer to make them for each job.

Open cell ridged foam works (like florists use to make floral arrangements) But it's not stiff.

For plate and grove vacuum fixturing, I have used soft fuel line tubing with good results. Think fuel line for your string trimmer or chain saw. Available by the foot at the hardware store.