Over on io9, I've been charting my progress on how to make a set of Stormtrooper armour, working off of a kit. But, how do you make the kit in the first place? You need a vacuforming machine.
This video from Punished Props goes over all the details of how one of these machines works. All you need are some straightforward tools that you'd find in any half-decent hardware store -- some angle aluminium, a Dremel, pegboard, and an all-important wet-and-dry shop vacuum -- and a bit of spare time.