Deceleration principle of twin-screw extruder

Ningbo Fangli Technology Co., Ltd. is a mechanical equipment manufacturer with nearly 30 years’ experiences of plastic pipe extrusion equipment, new environmental protection and new materials equipment. Since its establishment Fangli has been developed based on user’s demands. Through continuous improvement, independent R&D on the core technology and digestion & absorption of advanced technology and other means, we have developed PVC pipe extrusion line, PP-R pipe extrusion line, PE water supply / gas pipe extrusion line, which was recommended by the Chinese Ministry of Construction to replace imported products. We have gained the title of “First-class Brand in Zhejiang Province”.

In most extruders, the screw speed changes by adjusting the motor speed. The drive motor usually rotates at full speed of about 1750 rpm, which is too fast for an extruder screw. If it rotates at such a fast speed, too much friction heat will be generated, and the retention time of plastic is too short to prepare a uniform and well stirred melt. The typical reduction ratio should be between 10:1 and 20:1. In the first stage, both gears and pulley blocks can be used, but in the second stage, it is better to use gears and position the screw at the center of the last big gear. For some slow running machines (such as twin screws for UPVC), there may be three deceleration stages, and the maximum speed may be as low as 30rpm or less (ratio of 60:1). On the other hand, some long twin screws used for stirring can run at 600rpm or faster, so a very low deceleration rate and more deep cooling are required.

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