Experimental validation of simulated weld line formation in injection moulded parts

The interest in weld line analysis of injection-moulded parts has increased in the past few years, mainly because of the ever-increasing requirements for the performance of injection-moulded items. Weld lines are formed when two melt fronts come in contact with each other. Whereas the total elimination of weld lines is not always possible without modifying the part geometry, their negative influence on part performance and appearance can be minimized. This can be done by trial and error experiments or by model prediction. The cost and time efficiency of the latter makes it a preferred route for weld lines analysis. Computer simulation packages of injection moulding are capable of accurately predicting the weld line location, but none of the current ones can predict the weld line contact angle or mechanical properties quantitatively. This paper focuses on the analysis of weld line formation and suggests ways to modify the finite element mesh to get better results.