1. Classification of injection molding machine screws: […]
1. Classification of injection molding machine screws: gradual screw, abrupt screw, general-purpose screw.
1) Gradual screw: Refers to the gradual transition of the groove depth from the deep groove in the feeding section to the groove in the homogenization section. It is mainly used to process non-crystalline plastics with a wide softening temperature range and high viscosity, such as polyvinyl chloride.
2) Abrupt screw: refers to the process of screw groove depth changing from deep to shallow in a short axial distance. It is mainly used to process crystalline plastics with obvious viscosity and melting point, such as polyethylene and polypropylene.
3) General-purpose screw: The length of the compression section is between the abrupt screw and the gradual screw, but the plasticization quality and energy consumption are worse than that of the special one, in order to meet the requirements of crystalline and amorphous plastics.
2. The L/D ratio of the screw of the injection molding machine: Compared with the extruded screw, the screw of the injection molding machine has a smaller L/D ratio. The screw length-to-diameter ratio of the injection molding machine is usually between 17-22, and it is often about 20:1.
3. Injection molding machine screw compression ratio: if the screw groove of the injection molding machine screw homogenization section is deeper, the compression ratio will be small, otherwise the compression ratio will be large.
The selection of the depth of the screw groove is mainly determined by factors such as the specific heat capacity, thermal conductivity, stability, viscosity, and pressure during plasticization of the processed plastic. But it should not be too deep, too deep will cause the screw to twist off due to excessive torque, or stop due to overload.