Injection molding machine components
1. The hopper
Thermoplastic material is supplied to molders in the form of samll pellets. The hopper on the injection molding machine holds these pellets. The pellets are gravity-fed from the hopper throat into the barrel and screw assembly.
2. The barrel
The barrel of the injection molding machine supports the reciprocating plasticizing screw. It is heated by the electric heater bands.
3. The reciprocating screw
The recipprocating screw is used to compress, melt, and convey the material. The reciprocating screw consists of three zones: the feeding zone; the compressing zone; the melting zone.
While the outside diameter of the screw remains contrast, the depth of the flights on the reciprocating screw decreases from the feed zone to the begainning of the meleting zone. These flights compress the material against the inside diameter of the barrel, which creates viscous heat. This shear heat is mainly responsible for meleting the material. The heat bands outside the barrel help maintain the material in the molten state. Typically, a molding machine can be have three or more heater bands or zones with different temperature settings.