Best Material for Dedicated fixtures to place on vacuum grid

[777funk]

I have a vacuum grid made of HDPE I believe. It came with my 2x3 CNC Router. It has a small vacuum pump that will hold parts down VERY well if the vacuum is air tight. But if it's not... well, let's put it this way MDF didn't work.

Anyways, I'm using the gasket material that allstaradhesives.com is selling. There is a grid on the table and on top of that I'm wanting to place specialized fixture boards dedicated to specific parts (guitar bodies and one for necks). It needs to seal pretty well. MDF leaked too much to work.

What are materials that will hold vacuum well?

I'm guessing that the following would be good in order of convenience but not necessarily cost:
1. Aluminum 3/8"-1/2" Sheet
2. Baltic Birch ply
3. Acrylic (plexiglas)

Anyone have experience with any of those?

[Drassk]

Stick to strictly nonporous materials: aluminum, acrylic, phenolic, PVC

They'll all work equally well for holding vacuum. Material choice after that comes down to other properties you might need (durability, price, dimensional stability). I've made other stuff work (as I have a high CFM pump) in a pinch like MDF, wood, etc but all my permanent fixtures are aluminum and any fixture to be used over any length of time is at least acrylic.

[777funk]

Ok thanks, So acrylic/Plexiglas... I would assume that plexi would hold up well if it was thick enough. I'd also think PVC should hold up well. And of course Aluminum aint budging! But the price... seems pretty expensive for even a small 2x4 foot sheet in 1/2" thickness.