UPDATE:
I ordered the motor, got it wired up and connected to a vacuum box that bolts to the bed of my machine. I have a vacuum gauge coming in the mail so I'll update later with how much vacuum I am pulling. I am thrilled with the suction this vacuum provides. My machine is a CNCRP 4x2 standard, and when I throw a 2x4 sheet of baltic birch on the vacuum table, I can't move it with all the force I can exert. Very cool.
However...I am having some trouble once I start cutting parts. I am leaving a 0.02" onion skin to maintain vacuum as long as possible, but when it comes time to cut full depth, I get a few parts that move. And not just small parts, some parts well over 100sq.in. It seems to happen only in certain regions of the bed. I'm not sure if this is because of a bad vacuum box design, or if there is warpage in some of the parts that causes vacuum loss once they get cut out.
Considering the success everyone else has with plywood on a vacuum table, I'm guessing my issue is coming from a bad design. The base of the box is 1/2" MDF. Glued onto the base are the frame pieces, measuring 2.5" tall. I started with a rectangle frame with two cross pieces in the center. When I put the 1/2" MDF top on and turned on the vacuum, the top is held in place very securely and doesn't go anywhere. BUT...the vacuum is so strong that it causes the MDF to bend between each cross piece. That was mind blowing. As a result, no sheet good would really make good vacuum with the table. So I added more 2.5" tall pieces to hold up those sections that were getting bent down and tried again. Still a tiny bit of pulling. So I glued the board down, and I believe it stays fairly flat with the vacuum on.
I ran a quick couple of cuts before surfacing the board and had 2 of 14 parts move. Not bad, but not good. I figured it was due to not being flat relative to the machine, so I surfaced the top and ran another little cut, with two parts that are only 50sq.in. One part stayed down very well and wouldn't move when cutting the onion skin, but the other part jumped around and lost vacuum. I'm at a loss. My spindle isn't perfectly trammed, but I only have a little ridge between each pass. Perhaps that is enough to cause vacuum issues, I don't know. Maybe the 1/2" MDF top is still getting pulled by the vacuum and I need to use a thicker top?
Do you guys have any suggestions?