Control of plastics extrusion

摘要

The speed of an extruder feeding means (F) driven by a motor (M3) is controlled so that the 'shot' time is maintained constant. The time taken for the pressure (PS1) of material extruded into the cup (C1) to reach a level indicating filling thereof is measured and compared with a preset time. The error signal (ES) is phi supplied to speed control unit (SC) and the motor speed regulated to reduce the error signal. Two reference times may be provided so that the motor speed is only altered when the shot time falls outside a desired range. The motor speed may be stepped.