1. The screw diameter (D) is related to the requested […]
1. The screw diameter (D) is related to the requested injection volume: injection volume = 1/4 * π * D2 * S (injection stroke) * 0.85;
2, the screw diameter (D) is inversely proportional to the highest injection pressure, and is proportional to plasticization;
3, crystalline plastics should be long (such as POM, PA); amorphous materials second (such as PS, PU, ABS); heat sensitivity is the shortest (such as PVC);
4. Responsible for the mixing, compression and pressurized exhaust of plastics. After the material in this section is almost completely melted, it may not be evenly mixed;
5. Responsible for the transportation, pushing and preheating of plastics, ensuring preheating to the melting point;
6. The length of the metering section is good for mixing. If it is too long, the melt will stay too long and the thermal decomposition will occur. If it is too short, the temperature will be uneven. Generally, it will occupy 20% of the proportion, ensuring that the plastic is fully melted and the temperature is uniform. Mixing evenly;
7. The plastic gradually melts, and the volume of the screw groove needs to be correspondingly decreased to correspond to the decrease of the geometric volume of the plastic. Otherwise, the material pressure is not real, the heat transfer is slow, and the exhaust gas is poor;
8. The compression section generally accounts for more than 25% of the length of the screw operation, but the nylon screw accounts for about 15% of the section. The plastic screw with high viscosity, fire resistance, low conductivity and high increase accounts for 40%, and the PVC screw can account for 100%. The ratio to avoid severe shear heat.
9, PVC and other heat-sensitive plastics should not stay too long, to avoid thermal decomposition, a shorter metering section can be used;
10. The deeper the depth of the feeding groove, the larger the conveying amount, but the screw strength should be considered. The shallower the measuring groove depth, the higher the plasticizing heat and the mixing function index, but the metering groove depth is too shallow. The heat increases, the self-generated heat increases, the temperature rise is too high, and plastic discoloration or charring is formed, which is particularly disadvantageous for heat sensitive plastics.
The screw is the heart of the injection molding machine. The quality of the screw is good or bad. The quality of the product of the injection molding machine is very good, so it is necessary to buy a good screw.