Method and apparatus for controlling the thickness of extruded stock

Abstract

The thickness of a cut length of a continuously extruded elastomer is controlled by sampling the weight of a section of the continuous extrusion at a running-weigh-scale each second; computing one-minute averages of the running-weigh-scale samples and storing 'A' to 'n' of the averages where 'A' is the newest and 'n' is the oldest stored average; sampling the extruder motor power draw each second; computing one-minute averages of the power draw and storing 'B' to 'm' of the averages where 'B' is the newest and 'm' is the oldest stored average; comparing the newest to the oldest power draw average to obtain a difference between the two and multiplying the difference by a constant indicative of the type of elastomeric material being processed through the extruder to obtain a power-draw deviation signal; sampling the weight of a cut length of material extrusion at a check-weigh-scale; comparing the check-weigh-scale value to the oldest 'n' stored running-weigh-scale one-minute average and to the power draw deviation to obtain a targeted running-weigh-scale average; comprising the targeted running-weigh-scale average to the newest 'A' stored running-weigh-scale one-minute average to obtain a deviation from the targeted value if one exists; and converting the deviation from the targeted running-weigh-scale value to a control signal for increasing or decreasing the speed of a take-away belt positioned at the extruder exit orifice to vary the thickness of the extrusion in accordance with the deviation control signal and the speed of the belt.