An introduction to automatic profile control

The author presents a brief introduction to measuring the profile variation of an extruded flat sheet and techniques for controlling that profile variation with a flexible-lip die. Profile control strategies are discussed, and attention is given to such issues as controlling to the average, creating nonflat products, neckdown, interaction across the die, heat transfer, and tuning. The purpose of automatic profile control is to shape the profile of the sheet. This requires adequate measurement of the sheet, with special attention to aligning the measurement data to the positions of the diebolts on the die