Dynamic braking of a melt pump for improved extrusion consistency

It is an industrial practice to reduce the output pressure variations from an extruder by using a gear pump between the extruder barrel and the die. This thesis investigates the use of a gear pump as a metering device with the drive system disconnected, the speed of which may be controlled using a tension brake. The tension brake may be held in closed loop control with the screw speed of the extruder to ensure uniform pressure at the output of the gear motor. In this way, a “melt brake” is created to improve the process consistency without the expense of a transmission or a drive motor. To validate the concept feasibility, experiments were conducted using a conventional gear pump without a drive system. The extruder melt pressure was used to drive the gear pump and the pressure drop across the gear pump was obtained as a function of melt temperature. (Abstract shortened by UMI.)...