Deceleration principle of twin-screw extruder

Here are some key points about the deceleration principle of twin-screw extruders:

1. Adjustment of screw speed

· In twin-screw extruders, changes in screw speed are usually achieved by adjusting the motor speed. The motor usually turns at a higher full speed such as 1750rpm, but this may be too fast for the screw, so it needs to be slowed down.

2. Deceleration ratio

· The typical deceleration ratio is between 10:1 and 20:1. The first stage can use a gear or block, but the second stage usually uses a gear and positions the screw in the center of the last large gear.

3. Energy consumption

· If the reduction rate is not properly matched with the work, it may cause waves. It takes too much energy. In some cases, it may be necessary to add a block between the motor and the first deceleration stage that changes the maximum speed to increase the available energy and reduce the current value to avoid motor failure.

4. Melt uniformity

· High-speed rotation may cause too much friction heat, making the plastic retention time too short to prepare a uniform melt. Appropriate deceleration can solve this problem and ensure the uniformity and quality of the melt.

5. Match with work

· The selection of the reduction rate needs to consider specific working conditions, such as the characteristics of the material, the required melt pressure yield, etc. For example, for some low-speed machines, such as the twin-screw used for UPVC, lower deceleration ratios may be required, perhaps even up to 60:1.

6. Structure principle

· In the design of twin-screw extruder, the geometry and arrangement of the screw also affect the implementation of the deceleration principle. For example, the tightly engaged screw design can reduce the gap between the screws and improve the conveying efficiency and melt uniformity.

Following these deceleration principles can effectively improve the performance and efficiency of twin-screw extruders and ensure product quality and output.