The application of plastic products is closely related to our lives. Injection molding and extrusion molding are currently processing the most economical and energy-efficient processing methods. Among them, the most important key components of plastic plasticizing screws have different physical properties for different plastics, which makes the design of plastic plasticizing screws different. For the design of plastic plasticizing screws, the use of empirical rules has always been costly and does not necessarily solve the problem. Therefore, some details on the design of plastic plasticizing screws are worthy of discussion and analysis.
Introduction to plastic plasticizing screw
The solid plastic raw material enters the screw channel from the feeding funnel, and the shearing effect of the screw is caused by the high-speed rotation of the screw, so that the plastic raw material is kneaded and transported along the screw groove to make the solid state The plastic raw material is heated by the heating sheet outside the melting tube and the shearing heat generated by the screw, so that the inside of the melting tube is heated to melt into a molten state.
The plasticizing screw can be divided into four zones according to its function:
1. Solid conveying zone
This section is joined to the feed funnel, and the plastic solid particles are tightly compressed to form a solid bed, which is subjected to the shearing effect of the melt cylinder, and the plastic is transported forward in addition to gradually increasing the temperature of the plastic.
2. Delay of melting
This section is the end of the solid transport zone to the former part of the melt pool. The main feature is that a thin film layer composed of melt rubber is formed on the surface of the solid bed and the melt cylinder, and the melt glue in the film layer is subjected to the melt cylinder. The drag force accumulates in front of the screw groove, and the pressure formed at the end of this zone is large enough to deform the solid bed, and the molten pool is gradually formed in the front screw groove.
3, melting zone (melting zone)
This section is the end of the melting delay zone until the plastic is completely melted. This zone can be divided into two parts. One is plastication, and the plasticization mainly comes from the shearing effect of the melt cylinder. The other is It is a melt conveying that delivers the melt to the melting tank.
