Thermoforming of plastic sheets over a model includes varying the thickness inthe area that is stretched over the model so that when it thins it becomesmore uniform in thickness. The plastic sheet (10) is fabricated in asubstantially uniform thickness but with a preformed a complex profile or 3Darea that partially builds in part of the area that would be stretched so thatit thins much less than a flat sheet. Combinations of these elements may alsobe made.
