The concept of a precision gear pump is very simple. Its basic form is that two gears of the same size are meshed and rotated inside a tightly-fitting shell. The inner part of the shell is similar to an"8" shape, two gears are mounted inside and the outer diameter and two sides of the gears are closely matched with the housing. The material from the extruder enters between the two gears at the intake and fills the space, moving along the housing with the rotation of the teeth and finally being discharged when the two teeth engage.

In technical terms, the precision gear pump is also called a positive displacement device, which is like a piston in a cylinder, when one tooth enters the fluid space of the other tooth because the fluid is incompressible, the liquid and the tooth can not occupy the same space at the same time, thus, the liquid is mechanically squeezed out. As a result of the constant engagement of teeth, this phenomenon occurs continuously, and therefore also in the pump outlet provides a continuous discharge, pump every turn, the discharge is the same. With the continuous rotation of the drive shaft, the pump also continuously discharges fluid. The flow of the pump is directly related to the pump speed.

There is very little fluid loss in the pump because these fluids are used to lubricate both sides of the bearing and the gear, and the pump body can never fit without clearance, so the fluid can not be discharged 100% from the outlet, so a small amount of fluid loss is inevitable, which makes the pump operating efficiency can not reach 100%. However, the pump still works well, and for most extruded materials, the efficiency is still 93% -98%.

The precision gear pump will not be significantly affected by process variations in viscosity or density. If there is a damper, such as a filter or a limiter on the side of the outlet, the pump will push the fluid through them. If the damper changes during operation, i. e. if the filter becomes dirty, or clogged, or the back pressure of the limiter increases, the pump will still maintain a constant flow rate, until the mechanical limit of the weakest part of the device (usually fitted with a torque limiter) is reached.

The speed of a precision gear pump is limited, depending on the process fluid. The pump can rotate at very high speeds if the oil is being transferred, but when the fluid is a high-viscosity polymer melt, this limit will be greatly increased.

It is very important to push the viscous fluid into the two-tooth space on the suction side. If the space is not filled, the pump will not be able to discharge the correct flow rate, therefore, PV (pressure × flow rate) is another limiting factor, and is a process variable. Because of these limitations, the precision gear pump manufacturer will offer a range of products with different specifications and displacements (the amount of output per rotation). These pumps will be matched with specific application processes to optimize system capacity and price.