What are the tanks for?

[ckrantz]

All,
I see vacuum forming machines and they have air tanks attatched to the vacuum pump. Why are they used? what do they do?

[Geof]

When you apply the vacuum to the mold you want things to suck down real fast before the plastic has time to cool. To do this you use a small or medium size vacuum pump to pull a bunch of tanks down to a good vacuum and then use the tanks to pull a vacuum on the mold very quickly.

[MGDriver]

To elaborate on what Geof said, vacuum pumps don't pump fast enough, so a vacuum is pulled on the tank instead of just letting the pump pull it on the part.