Plastic profile extruder melt-pump

The melt pump (also called gear pump or melt gear pump) in the plastic profile extruder is a key auxiliary equipment, which is mainly used to stabilize the melt pressure in the extrusion process, improve the output and product quality. The following is a detailed analysis of the melt pump:

1. The role of the melt pump

Stabilize pressure: eliminate pressure fluctuations caused by extruder screw fluctuations, to ensure uniform melt output.

Increase output: through the pressurization function, reduce the load of the extruder, improve the extrusion efficiency (especially for high viscosity materials).

Energy saving and consumption reduction: Reduce extruder back pressure, reduce energy consumption by 10%-30%.

Precise control: linkage with the control system, realizing closed-loop adjustment of flow and pressure, and improving dimensional accuracy.

2. Structure and working principle

Core components:

Gear set: usually consists of two gears (main wheel and driven wheel) meshing with each other, made of high-strength alloy steel (e.g. 38CrMoAl) with nitriding treatment on the surface.

Pump body: high temperature and high pressure resistant design with heating/insulation device (e.g. electric heating ring or thermal oil channel).

Bearing system: needs to be resistant to wear and high temperatures (e.g. sliding bearings or special ceramic bearings).

Sealing devices: to prevent melt leakage (e.g. screw seals or hydraulic seals).

Workflow:

Melt enters the suction end of the pump from the extruder → gears mesh to push the melt to the outlet end → pressurized and stable output to the mold.

3. Applicable scenes

Material type: Suitable for PVC, PE, PP, ABS, PC and other thermoplastics, especially effective for shear-sensitive or high-viscosity materials (such as TPU, engineering plastics).

Profile application: door and window profiles, pipes, plates, sheets and other high-precision extruded products.

4. Selection of key parameters

Flow range: Selected according to extrusion output (e.g. 50-5000 kg/h).

Pressure capacity: usually up to 40MPa, need to match the mold resistance.

Temperature control: Heating accuracy ±1℃ to avoid material degradation.

Material compatibility: gears and pump body need to be corrosion resistant (e.g. chrome plating or special coating when handling PVC).

5. Advantages and limitations

Advantages:

Reduced extruder wear and extended screw life.

Improves product surface finish and reduces defects (e.g. flow marks, bubbles).

Limitations:

Higher initial investment, suitable for high volume production.

Requires regular maintenance (e.g. gear lash adjustment, seal replacement).

6. Installation and Commissioning Recommendations

Position: usually installed between the extruder and the mold, as close to the mold as possible.

Joint control system: synchronize speed regulation with extruder and haul-off equipment to avoid flow mismatch.

Through rational selection and use of melt pumps, the stability and efficiency of plastic profile production can be significantly improved, especially for high-precision or thin-walled profiles is crucial. In practice, the parameters should be optimized according to the material characteristics, production rhythm and equipment configuration.

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