best of all, this method involves no fumes!
I'm gonna show you how to make plastic wheels for your robot!
I first heard about stewing plastic bags to make new things from Dave Huebsch's book " Village Assignment " about interesting adventures had while running a charity/NGO (" Common Hope ") in Guatemala. He, amazingly, repaired the bottom weight-carrying main bearing of a washing machine with a big plastic disc made of stewed plastic bags, which actually was such a good stand-in replacement that it held up for several years. (and here are some more Guatemalan Handy Tricks)
I had to try it right away, and the first couple times I just burnt plastic, until I came up with this method.
By the end of this, you'll be able to make yourself a knife sheath, mold around your shoes and make DIY hard-toe sneakers, wheels, bearings, bushings, or any kind of plastic part! Take pictures and post them in the comments!