Vacuum forming: how much vacuum?

[Rovingjack]

Right I've been planning to build a vacuum forming table (small scale to use shampoo bottles and water/milk jugs to make sections that can be glued or friction welded to create larger items). My plan is to make it as simple as possible. box about the size of a fuse box, with two or three layers of different sized screen material at slightly different angles so the screens reinforce each other but air flows through everywhich way. then just two frames sandwhiching the plastic sheet. Might get a thrift store toaster oven but could also just use a metal box made out of some flashing and circulating air from a heat gun I have.

The real question is- what do I need in a vacuum? As it would happen I'm in the market for a shop vac anyway and am looking at different models and prices. I'm noticing that some are 2 hp and some are under. I don't need large volumes of space, nor do I need the fourty dollars extra price... unless it makes all the difference in vacuum forming quality.

or is it even a matter of horsepower in pulling a vacuum?

 

[tictoc]

I use a 2.5 HP shop vac and It works fine for positive mold bucks for greeblies, helmets, armor etc. etc. i.e. resulting in your typical vacuum form look. For super detail you are going to need a tank.

IMHO It is more important to have even heating over the surface of your plastic. My oven is a box lined with flashing and a lid. The heat comes from two electric barbeque grills. The second most important aspect is the kind of plastic you choose.

Pick up a copy of Vacuum Forming by Douglas Walsh and experiment. It's lots of fun.

 

[asalaw]

Generally go for as much suction as you can afford. Most people use a regular shop vac. But making your holes as tiny as possible is also important, since that helps you get higher pressure all on its own. The rest is really experimenting with your plastics, how long they need to be heated at which thicknesses, and so forth. We have an industrial one at Techshop, and it still requires experimentation.