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


If the deceleration rate is not matched with the work, too much energy will be wasted. At this time, it may be necessary to add a pulley block between the motor and the first deceleration phase to change the maximum speed, which will either increase the screw speed or even exceed the previous limit, or reduce the maximum speed. This can increase the available energy, reduce the current value, and avoid motor failure. In both cases, the output may increase due to the material and its cooling needs.


If you need more information, Ningbo Fangli Technology Co., Ltd. welcomes you to contact for a detailed inquiry, we will provide you with professional technical guidance or equipment procurement suggestions.

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