Design and Construction Principle of Screw of Plastic 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”.

Feeding area of plastic extruder: the fixed groove depth of screw groove, which is responsible for preheating, plastic solid conveying and extrusion. It must be ensured that the plastic starts to melt at the end of the feeding section - that is, it must be preheated to the melting point. The general length is about 48~58% L for amorphous (AS, ABS, PS), 48~58% L for crystalline (PA, POM, PE, PP, CA), and 45~55% L for glass fiber added.

Compression area of plastic extruder: the depth of the screw groove of the tapered screw is deep, and its function is to melt, mix, shear compress and pressurize the plastic raw materials. The plastic will completely dissolve and the volume will shrink in this period, so the design of the compression degree is very important. The general length is about 25-35% L for amorphous (AS, ABS, PS), 22-32% L for crystalline (PA, POM, PE, PP, CA), 28-40% L for glass, and 100% L for thermal sensitivity (PVC).

Measuring area of plastic extruder: screw groove is fixed in depth. Besides its main functions of mixing, glue conveying and metering, sufficient pressure must be provided to maintain uniform temperature of glue melt and stable flow of molten plastic. The general length is about 15 ~ 58% L for non-crystalline (as, ABS, PS), about 48 ~ 58% L for crystalline (PA, POM, PE, PP, CA, etc.), about 45 ~ 55% L for glassiness.

Although the screw of the plastic extruder can be distinguished according to its function or geometric construction, it is difficult to distinguish them due to the overlapping functions of each section in the actual plasticizing process. The research of plasticizing screw is to improve the shear mixing effect, improve the uniform mixing, improve the plasticizing ability and improve the temperature uniformity of melt. When the tooth depth of the feeding section is deeper, the conveying capacity is larger, but the torque required by the screw is larger; and if it is too shallow, the conveying capacity is insufficient, and the compression ratio is insufficient. When the tooth depth of the metering section is too deep and the compression ratio is insufficient, the required feeding force is large; and it is easy to burn when it is too shallow. The general tooth depth is about 0.03 ~ 0.07 times the screw diameter. Therefore, plastic plasticizing screw has the functions of conveying, melting, mixing, compression and metering, and plays an important role in plasticizing quality.

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.