[erikpurne]

FACT: Everyone knows that gas heated ovens work regardless of what ever we decide to put into them -- if this wasnt so then few of us would ever have eaten a hot dinner, roasted a turkey, baked bread and a multitude of cakes and cookies ... all cooked at different temperatures and times. Even the dumbest housewife eventualy learns how to use a gas oven. So why not dispell some myths and use one yourself -- only bigger?
Sure nichcrome wires will heat up an oven (given long enough) On Utube we see kids producing all manner of plastic parts using mums oven and a vacuum cleaner.
So build a gas oven in which to place your valuable plasic and heat it until its ready to form. If you want the details on how to build an oven then open any oven door --and take a look at what is inside, okay!
Now measure the size of the plastic you want to heat and build your oven. You can wreck any old oven and take the parts from within -- including the temperature controller and thermometer if needed. Just construct YOUR oven a little, or a lot, larger. Its as simple as that! No but's no If's. But If -- 'your custom oven' doesnt work, then say goodbye to any more hot dinners as things must be changing very rapidly and there will never be any more roast beef, lamb, chicken and turkey on any menu ever again -- ever!
Construct it -- Use it -- Form it. (No rocket science required )

FACT: Despite the condescending tone of this post implying that the answer is obvious and you're an idiot if you don't see it or can't do it, making your own gas oven for thermoforming is a terrible idea.

Nobody is doubting that a gas oven will heat the plastic, nimrod. However, like others have mentioned, it is vital to be able to precisely control the temperature of different zones (for example, the ones we use have 36 independently controlled panels.)

Indeed, no rocket science required, but some basic knowledge of the subject matter is.