Myself and Nathan are involved in building up Precious Plastic in Lancaster (see here) and prior to the ‘official’ machines being built and used, we thought we’d see what we could come up with trying to form a coathanger (PP) into a coaster that looked good, was functional and valuable just using things in the garage (albeit quite a nice one).
It took a while experimenting starting to use a tin can to then using a wooden mould and arbor press but we achieved what we wanted to. I think the biggest limitation was the mould. Smooth-sided aluminium moulds I think are the way to go in order to heat them and for the plastic not to stick.
Indeed, the heatgun was the main tool and this was from when I used to repair xbox360 consoles. The mould and ability to add pressure were the more tricky things although we did get a nice result just under gravity using an empty food can!