A melt pump, also known as a melt gear pump, is a precision pressure-stabilizing and metering device specially designed for plastic extrusion lines. It plays an irreplaceable role between the screen changer and the die head in the extrusion workflow.
The typical layout of an extrusion line runs in this order: Extruder → Screen Changer / Filter → Melt Pump → Die / Mold. While the extruder melts and conveys raw polymer materials, and the filter removes impurities, the melt pump takes charge of regulating the molten polymer before it enters the mold.
How Does a Melt Pump Work?
The core component of a melt pump is a pair of precision meshing gears. Molten plastic flows into the pump through the inlet, fills the gear tooth cavities, and is continuously carried to the outlet as the gears rotate.
It belongs to **positive displacement conveying equipment**. Its output flow has a nearly linear relationship with rotating speed. Operators can accurately control melt delivery simply by adjusting the pump speed.
Core Functions of the Melt Pump
Three primary advantages make melt pumps popular across film, pipe, granulation and profile extrusion industries:
1. Pressure Stabilization: It absorbs pressure pulsations from the extruder, maintaining stable pressure for the downstream die.
2. Precise Metering: Delivers a consistent, fixed volume of polymer melt.
3. Stable Conveying: Keeps melt flow uniform and steady all the time.
In short, the melt pump enables the polymer melt to enter the die in a more stable and controllable state. It greatly reduces product thickness deviation, improves finished product consistency, lowers scrap rates, and helps extrusion factories achieve reliable high-volume production.
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