Focus on extrusion screw manufacturing for 30 years
Description of screw's usage and introduction of plastic scr
Description of screw's usage and introduction of plastic scr
The solid plastic raw materials enter the screw channel from the feeding funnel, and the screw rotates at high speed to produce shear effect with the barrel, so that the plastic raw materials are mixed and transported along the screw slot, and the solid plastic raw materials are heated by the electric heating plate outside the barrel and the shear heat generated by the screw, so that the inner part of the barrel is heated to form a molten state. What is injection screw of plastic machine? What are the characteristics of screw? The application of plastic products is closely related to our life. Injection molding and extrusion molding are currently the most economical and energy-saving processing methods. The plastic screw is the most important key component, which has its own physical characteristics for different plastics, so the design of plastic screw is also different. For the design of plastic screw, the rule of thumb has been used in the past. The cost is high and it can not solve the problem. Therefore, some details in the design of plastic screw are worthy of our discussion and analysis. According to its function, the plasticizing screw can be divided into four zones: 1. Solid conveying zone. This zone is connected with the feeding funnel. The plastic solid particles are tightly compressed to form a solid bed. Due to the shear effect of the melt rubber cylinder, the plastic is transported forward in addition to gradually increasing the plastic temperature. 2. Delay of melting this section is the area from the end of the solid conveying area to the area before the formation of the melt pool. Its main feature is that a film layer composed of melt adhesive is formed on the surface of the solid bed and the melt adhesive cylinder, and the melt adhesive in the film layer is affected by the drag of the melt adhesive cylinder The pressure formed at the end of this zone is large enough to deform the solid bed, and the melting pool is gradually formed in the front screw groove. 3. This section of the melting zone is from the end of the melting delay zone to the end of the plastic melting. This zone can be divided into two parts for discussion. One is plasticization, which mainly comes from the shear effect of the melt barrel, and the other is melt conveying, which transports the melt to the melt pool. 4. Melt conveying zone starts to enter this section when all plastics are completely melted, and ends at the end of plasticizing screw to maintain uniform melt temperature and stable flow of molten plastics. According to the geometric shape, the plastic screw can be divided into three sections: this section is to fix the groove depth of screw groove, and its function is responsible for preheating, plastic solid conveying and pushing. It must be ensured that the plastic begins to melt at the end of the feeding section (i.e. preheat to the melting point). The length of this section is divided into crystalline (POM, PA, etc.) > non crystalline (PS, PU, ABS, etc.) > thermal sensitivity (PVC, etc.). Generally: non crystalline: about 48 ~ 58% L (as, ABS, PS, etc.) crystallinity: about 48 ~ 58% L (PA, POM, PE, PP, CA, etc.) glass addition: about 45 ~ 55% L 2, metering zone. This section is screw screw groove with fixed groove depth. Besides its main functions of mixing, melt glue conveying and metering, it must also provide sufficient pressure to maintain uniform melt glue temperature and stable melt plastic flow. General length: amorphous: about 15 ~ 58% L (as, ABS, PS, etc.) crystallinity: about 48 ~ 58% L (PA, POM, PE, PP, CA, etc.) glassiness: about 45 ~ 55% L 3, compression zone. This section is the screw groove depth of tapered screw, and its function is melting, mixing, shear compression and pressurized exhaust of plastic raw materials. In this section, the plastic will be completely dissolved and the volume will be reduced, so the design of compression degree (compression ratio) is very important. General length: amorphous: about 25 ~ 35% L (as, ABS, PS, etc.) crystallinity: about 22 ~ 32% L (PA, POM, PE, PP, CA, etc.) glass addition: about 28 ~ 40% L, PVC: 100% L.
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