My 1989-vintage Ron Charles Vacuum Forming machine has a 9x12 inch platen that
is simply perforated steel plate, there must be well over a thousand holes in
it. For suction, it uses, believe it or not, the motor, impeller and volute
unit from a Kirby Vacuum Cleaner, which moves a helluva lot of air, very
For successful vac-forming, it's necessary to remove the air between the hot
plastic and the platen & master fast, fast enough so that it sucks down the hot
plastic almost instantly, before it has a chance to cool. You mention .75mm
styrene, that is the same (for all intents and purposes) as .030" thick, and
that thickness of styrene is eminently formable by vacuum, provided it is hot
enough (it should be as soft as a sheet of soft rubber!).
Laboratory vacuum pumps are fine for many things, but vac-forming really isn't
one of them, as lab pumps are just too slow. They get their advantage by
removing air slowly, but completely, to at least 29" of mercury, which I
understand to be a mechanically perfect vacuum for most applications.
Take the advice you have already gotten, use a shop-vacuum to extract the air,
those are more than powerful enough for vacuum forming, and certainly quick
enough, due to the volume of air they are capable of moving per minute--lab
pumps are not, from all the lab pumps I've seen.