SIMPLE MODELS FOR AN INJECTION
MOLDING SYSTEM

GREGORY LEWIS, IAN FRIGAARD, HUAXIONG HUANG,
TIM MYERS, REX WESTBROOK AND MARIANA
CARRASCO-TEJA

Based on work carried out at the Eighth Annual Industrial Problem Solving Workshop, sponsored by the Pacific Institute for the Mathematical Sciences, May 17-21, 2004. Original problem submitted by Husky Injection Molding Systems.

Abstract. We develop simple models that can be used to predict the forces of impact that occur during the injection molding process involving a magnesium alloy. We model the impact of the injection molding screw tip on the molten material entering the mold, and the impact of the piston flange on the machine housing, which can occur when the amount of material that has been injected into the mold is insufficient to completely fill the mold. We consider the effects due to the elasticity of the molten material and machine parts, those due to the presence of a thin film of hydraulic fluid between the piston flange and machine housing, the variation of the viscosity of the hydraulic fluid, and those due to the leakage of molten metal past the screw tip.
With the simple models developed here, an injection molding machine designer can predict how varying the process parameters may affect the impact forces, and thus, may be able to more efficiently design the machine so that damage is less likely to occur during operation. This will result in a longer life for the machine, which will lead to increased cost effectiveness for the manufacturer.