The Role of Each Section of the Injection Molding Machine Screw

2021-10-20


The role of each section of the injection molding machine screw

1. The role of injection molding machine screw conveying section

The screw conveying section of the injection molding machine is responsible for the conveying, pushing and preheating of the plastic. The material should reach the melting point temperature through the conveying section. Generally, the injection molding machine screw conveying section accounts for about 50% of the total length of the injection molding machine screw.

The deeper the groove depth of the conveying section, the greater the conveying capacity, but the actual design needs to consider the strength of the injection molding machine screw.


2. The role of injection molding machine screw compression section

The injection molding machine screw compression section is responsible for plastic compression, pressurization and exhaust. The materials have almost all dissolved after passing through this section, but there is no uniform mixing. Generally, the compression section account for 20%-25% of the total length of the injection molding machine screw. In this area, the plastic gradually melts, and the volume of the injection molding machine screw groove must be gradually reduced, otherwise the material will not be compacted, the heat transfer will be slow, the exhaust will be poor, and it will also cause the formation of pores in the work piece.

The injection molding machine screw compression ratio is the ratio of the depth of the last groove in the feeding section to the depth of the first groove in the metering section. When the compression ratio is constant, the longer the injection molding machine screw compression section, the smaller the shear heat. Similarly, if the compression section length is constant, the smaller the compression ratio, the smaller the shear heat is, so the compression section structure is the main part that determines the magnitude of the shear heat.

Generally, the compression ratio of the injection molding machine screw with low shear heat is 1.8-2.2, and the h2 (the depth of the groove in the metering section) is 0.09-0.1D (the screw diameter).


3. The role of the injection molding machine screw metering section

The metering section of the injection molding machine screw generally occupies 20%-25% of the total length of the injection molding machine screw. It is mainly responsible for the uniform mixing of the plastic and ensuring that the plastic is completely melted.

If the metering section is long, the plastic mixing effect will be good. If it is too long, the melt will stay for too long and cause thermal decomposition. If it is too short, the temperature of the material will be uneven.

Generally, when we select the injection molding machine to process products, the best product weight to injection molding machine is 70%-80% of the injection volume. If the injection volume is too large, the melt will stay in the metering section for a long time, resulting in thermal decomposition of the material and pores in the final product. It even affects the mechanical properties of the product.

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