Selecting Injection Molding Screws

Screw DesignThe basic design of any screw has 3 zones along its length:1. Feed zone2. Transition zone3. Metering zoneThe feed zone conveys the solid plastic pellets which are fed from the hopper to the transition zone where they are compressed by a change in screw geometry. This compression forces the pellets to melt through the action of pushing up against each other. This is called shearing. The metering zone then conveys the melt to the front of the screw ready for injection into the mould cavity.