The concept of a gear pump is very simple, that is, its most basic form is that two gears of the same size mesh with each other in a tightly fitting shell. The inside of the shell is similar to a figure eight, and two gears are installed in it. The outer diameter and both sides of the tube are closely matched with the shell. The material from the extruder enters the middle of the two gears at the suction port, and fills this space, moves along the housing with the rotation of the teeth, and is finally discharged when the two teeth mesh.

When one tooth enters the fluid space of another tooth, the liquid is mechanically squeezed out. Because the liquid is incompressible, the liquid and the tooth cannot occupy the same space at the same time, so the liquid is eliminated. Due to the continuous meshing of the teeth, this phenomenon occurs continuously, so a continuous discharge amount is provided at the outlet of the pump, and the discharge amount is the same for each revolution. With the uninterrupted rotation of the drive shaft, the fluid is continuously discharged. The flow of the gear pump is directly related to the speed.