What is the role of injection molding machine screw head?

Published on:

2023-04-07

In the injection screw, the role of the screw head is: in the pre-forming process, the plasticized melt can be discharged into the storage chamber, and in the high-pressure injection process, the melt in front of the screw head can be effectively dense

What is the role of injection molding machine screw head?

In the injection screw, the role of the screw head is: during the preforming process, the plasticized melt can be discharged into the storage chamber, and during the high-pressure injection process, the melt in front of the screw head can be effectively sealed to prevent backflow.

Screw heads are divided into two categories, those with stop rings and those without stop rings. For products with a back-up ring, during the preforming process, the melt in the screw homogenization section pushes the back-up ring away and flows into the storage chamber through the gap formed by the screw head. During the injection process, the melt pressure of the screw head forms a thrust force to return the retaining ring to the flow channel to block and prevent backflow.

For some materials with higher viscosity, such as PMMA, PC, AC or PVC with poor thermal stability, in order to reduce the shearing effect and the residence time of the material, it is not necessary to use a retaining ring, but such injection will produce backflow and prolong the residence time. time.

Screw head requirements:

①The screw head should be flexible and smooth;

②The gap between the retaining ring and the barrel must be appropriate, which must prevent the melt from flowing back and be elastic;

③ There should be sufficient flow cross section, and the end face of the retaining ring should have a restoring force so that it can be closed quickly during injection;

④The structure should be easy to disassemble and clean;

⑤ The thread direction of the screw head is opposite to that of the screw to prevent the screw head from loosening during preforming.

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How much do you know about the maintenance method of the barrel?

What are the requirements for the production of PC material for injection molding machine barrel and screw?