The problem in a certain thermoforming operation is that there k too much thinning in the walls of the large cup-shaped part. The operation is conventional pressure thermoforming using a positive mold, and the plastic is an ABS sheet with an initial thickness of 3.2 mm.
(a) Why is thinning occurring in the walls of the cup?
(b) What changes could be made in the operation to correct the problem?