Why does an extruder need a melt pump? What does a melt gear pump do? Simply put, it takes over part of the pressure-building work from the screw and helps maintain a steadier flow into the die. In sheet, film, pipe and pellet production, uneven thickness, dimensional changes and inconsistent strand sizes can sometimes be traced to fluctuations in melt output.
The extruder screw must melt and mix the material while conveying it forward. Changes in material feed, processing temperature or filter resistance can cause pressure and flow at the die inlet to fluctuate. Operators often adjust the screw speed first, but this also affects melting and mixing, so it may not be enough to stabilize the output.
Installing a melt pump between the extruder and the die allows the pump to handle part of the pressure-building and metering work. The screw melts and feeds the material, while the melt gear pump continuously conveys it through rotating gears. With sufficient inlet feed and a suitable processing temperature, pump speed can be adjusted to control the flow rate. This helps reduce the effect of upstream fluctuations on die output and makes product dimensions easier to control.
A melt pump cannot solve every production problem. Incomplete melting, insufficient feed to the pump, or problems with the die or haul-off equipment still need to be checked individually. Pump selection should consider the material, throughput, temperature, viscosity, and inlet and outlet pressures, along with the screen changer and control system.
Tianjin Ruicheng Pump Industry Co., Ltd. manufactures melt pumps and complete pump assemblies. Pumps can be selected according to the operating parameters of the extrusion line to meet pressure-building, flow stabilization and metering requirements.
