Extrusion die control system

摘要

The thickness of plastic film extruded from a die is maintained at a desired uniform dimension by utilizing the thermal expansion and contraction of die adjusting bolts to control the width of the orifice of the die. A thickness gauge measures the film thickness across its transverse dimension and provides a signal to a microcomputer which uses the information to calculate the desired die bolt movements. The movements are converted to bolt temperature changes to change the set temperature of each die bolt. A temperature sensing element in the die bolt provides a temperature signal to the microcomputer which controls the amount of power output to each bolt to attain the new set temperature. The temperature sensing and control system provides greater sensitivity, accuracy, and faster response to changing conditions than systems relying only on measurement of thickness variations to control power output to the bolt heaters without using bolt temperature for feedback.