Calculations for Injection-Molding Plasticators

Rotational flow and pressure flow rate calculations for the screw geometry and process conditions are performed for the injection-molding process in the same manner as for an extrusion process. Since the plasticator of an injection-molding process is not a continuous process, the instantaneous rate must be calculated based on the time that the screw is actually rotating. The instantaneous rate is the rate that is compared to the calculated flow rates for the screw. The instantaneous specific rate is calculated as follows  

The pressure at the tip of the screw is controlled by setting the hydraulic back pressure at the shank end of the screw. The pressure at the tip is calculated from the hydraulic back pressure and the process intensification factor as follows  

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