The vacuum clamp is now working like a charm. I also tried a new router collet and I was able to route a box with no problems.
After thinking about this (and getting suggestions), I changed the way it works. The new concept is to pull the work piece all the way to the flat of the HDPE clamp plate which will supply a flat, level and strong grip. I added dados that are just a bit shallower than the foam is thick. I also drilled a two inch ‘well’ for the vacuum to grab onto the wood. Yes, she sucks now. Thank you very much.
I still have to seal the bottom of the wooden work piece. I just used sanding sealer which dries pretty fast. With it I can pull 27 inches of Hg and my pump shuts off (I have a vacuum gauge). Without sealing the work piece the best I could pull was 18 inches, the pump never shut off, and I could twist the wood. So I will seal the wood first. But I can deal with this.
So to do a little math, 27 inches of Hg is the same as 13.25 psi of pressure. My small foam outline is 2.5” x 3” = 7.5 square inches. So 13.25 * 7.5 equals 100 pounds of pressure. I plan to add extra dados to be able to increase the total area when using larger work pieces. The foam is able to be reused and moved from dado to dado.
I remember now why I stopped using this CNC. It takes so much time to get everything right. I keep thinking I am close, but maybe this time….
-- -- I'm no rocket surgeon