The plasticizing screw of the injection molding machine has the functions of conveying, melting, mixing, compressing, metering and exhausting. It plays an important role in the plasticizing quality and is a key factor affecting the plasticizing quality. There are several crucial parameters of the screw that affect the plasticization quality. Generally, the following principles are used to select the bimetallic screw
of the injection molding machine:1. Screw diameter (D)
a. It is related to the required injection volume: injection volume = 1/4*π*D2*S (injection stroke)*0.85, b. Generally speaking. The screw diameter D is inversely proportional to the maximum injection pressure. It is proportional to the plasticizing ability proportional.2. Conveying section
a. Responsible for plastic transportation. Push and preheat. It should be preheated to the melting point. B. Crystalline plastics should be longer (such as: POM.PA) and amorphous materials (such as: PS.PU.ABS). The shortest thermal sensitivity (eg: PVC).3. Compression segment
a. Responsible for the mixing of plastics. Compression and pressurized exhaust. The raw materials passing through this section have been almost completely melted. However, they may not be uniformly mixed. b. In this area, the plastics are gradually melted. Corresponding to the decrease of the geometric volume of the plastic. Otherwise, the material is not compacted. The heat transfer is slow. .High viscosity. Fire resistance. Low conductivity. Plastic screw with high additives. Account for 40%//50% of the working length of the screw. PVC screw can account for 100% of the working length of the screw. To avoid intense shear heat.4. Metering section
a. Generally account for 20//25% of the working length of the screw. Ensure that the plastic is fully melted and the temperature is uniform. The mixing is uniform. b. The metering section is long and the mixing effect is good. If it is too short, it is easy to make the temperature uneven. C. PVC and other heat-sensitive plastics should not stay for too long. To avoid thermal decomposition. Use a shorter metering section or no metering section.5. Feeding groove depth. Measuring groove depth
a. The deeper the depth of the feeding groove, the greater the conveying capacity. However, the strength of the screw needs to be considered. The shallower the depth of the metering groove, the plasticization and heat generation. Heat increases. Self-generated heat increases. The temperature rise is too high, causing the plastic to discolor or burn. It is especially unfavorable for heat-sensitive plastics. .