I need to set my shopbot up to machine very small parts from solid hardwoods (I'm a puzzlemaker). I've been thinking about various implementations including pneumatic clamping and toggle clamps, but if I can get vacuum clamping to work it will vastly increase productivity because there will be less time fussing around between runs. However, I'm having trouble quantifying whether or not it will actually work, and I'd like to know it will before I drop a ton of money on the project.
For instance, cutting notches in burr puzzles. Because some material in the middle is usually removed from the pieces, and they are machined on two of four faces, my total area for vaccuum is two square inches. Say I mill out slots for the pieces to fit in to 1/4 inch depth, and use 1/8" sunken gasket to achieve excellent fit. Absolute vac is something like 14 psi, so by the time I use up the gasket area and leave a .05 shoulder for support, my total area to hold the piece down is really .845 square inches. Assuming less than perfect vaccuum of 8 psi, lets call it 6.75 lbs of presure holding the piece down.
Is that enough to hold down a 1"x3" stick of hardwood (reinforced on the sides by the recessed slot) while it has grooves cut in it? Is my guesstimate of 8psi achieveable with say a fein?
To get an idea of the sort of pieces I need to clamp, here's a picture:
http://www.toysfromtimespast.com/toys/318-2.jpg