What is the working principle of a melt pump?
Author：Heiko IndustryDate:2021-11-15 17:07:21

A melt pump is a positive displacement conveying device, and its flow rate is strictly proportional to its rotational speed. It mainly consists of a pump casing, driving gear, driven gear, sliding bearings, front and rear end plates, packing seals, and other components.

The tooth profiles of the two gears, the pump body, and side cover plates form the pump’s feed zone, conveying zone, and discharge zone. During operation, the melt is conveyed by the change in working volume caused by the meshing of the driving and driven gears. The working volume (i.e., the feed zone) is formed by the pump body, the tooth spaces of the gears, and the bearings that function as side plates. As the gears rotate in the specified direction, the melt enters the tooth spaces of the two gears in the feed zone. As the gears rotate, the melt is carried into the conveying zone from both sides. The re‑meshing of the gears forces the melt in the tooth spaces out of the discharge zone and into the outlet pipeline. As long as the pump shaft rotates, the gears push the melt toward the outlet side. Therefore, the pump outlet can achieve a very high pressure, while there is no strict requirement for inlet flow rate and pressure; it can even operate with vacuum suction at the inlet.

Melt pumps are widely used in the extrusion molding of plastics, resins, and rubber products, such as pelletizing, film, pipe, sheet, and plate production. According to tooth orientation, they can be classified into spur gears, helical gears, herringbone gears, etc.