ORIGINAL: marty-vf
ok. sag is not always a bad thing you can actually use the sheet sag to your advantage, for example if you're making a nose cone or male molds invert your mold upside down
and you could actually eliminate alot of problems.
Do you mean suck the plastic upward onto an inverted mold, or use a female (cavity) mold?
also try to control the flow of your vacuum, too fast of a suction will also produce webs.
Any hints on how fast is too fast? How long should it take to suck the plastic down?