Explain the reduction principle of a small extruder

Micro extruder has been widely used in China, and the principle of its reduction is:

In most extruders, changes in the screw speed are achieved by adjusting the motor speed. The motor usually rotates at about 1750rpm full speed, but it's too fast for an extruder screw. If you rotate at such a high speed, you will produce too much friction heat, and the plastic residence time is too short to prepare a uniform, very good mixing of the melt. The typical deceleration ratio is between 10:1 and 20:1.

The first stage can be either a gear or a pulley block, but the second stage uses gears and the screw is positioned at the center of the last big gear. In some slow running machines (such as double screw for UPVC), there may be 3 deceleration stages, and the maximum speed may be as low as 30rpm or less (60:1).

The other extreme is that some of the long twin-screw pairs used for mixing can run at 600rpm or faster, so a very low rate of deceleration is required and a lot of deep cooling is required. Sometimes the rate of deceleration matches the task incorrectly - too much energy is not available - and it is possible to add a pulley block between the motor and the first deceleration phase that changes the maximum speed.