[andy]

I do not think that you have enough compressor "umph" to efficiently implement a venturi vacuum generator. I also would quicly discount centrifigal vac pumps (there heavy- upwards 100 lbs) and turbo molecular vacs (expensive-upwards $15000).

I would try to drive a pnumatic cylinder with a cam on a motor with one way valves that seems like the easiest, lightest, most cost effective solution.

good luck!
-Andy