What does a melt pump do in PET sheet extrusion? When sheet thickness varies, operators usually check the die gap, rollers, and haul-off speed first. However, if the melt flow entering the die keeps fluctuating, adjusting downstream settings alone may not provide stable results.
During PET sheet extrusion, changes in screw output, melt viscosity, and filter resistance can affect the pressure and flow rate upstream of the die. A melt pump uses rotating gears to provide continuous positive-displacement conveying, pressurizing and metering the melt. This helps reduce the impact of upstream fluctuations on die feeding and provides more stable conditions for sheet thickness control.
The melt pump can also take over part of the pressure-building duty, allowing the extruder to focus more on plasticizing the material. However, the pump requires an adequate, continuous melt supply. Increasing pump speed cannot compensate for insufficient feeding. During operation, extruder speed should be adjusted according to pump inlet pressure, while pump outlet pressure and melt temperature should also be monitored.
For sheet extrusion lines processing recycled PET, filtration is another important consideration. A suitable screen changer is typically installed upstream of the melt pump to reduce the entry of hard contaminants into the pump chamber.
Tianjin Ruicheng Pump Industry Co., Ltd. can select melt pump displacement, drive, and sealing configurations based on actual operating conditions, including PET sheet output, operating temperature, melt viscosity, and inlet and outlet pressures, providing pump selection support for sheet extrusion.
