Prediction of weld line strength in injection moulded parts made of unreinforced amorphous thermoplastics

During the production of injection moulded parts the formation of weld lines is usually unavoidable. These embody often mechanical weaknesses. There are, however, currently no methods available that allow for a reliable design of plastics parts while taking the mechanical influence of the weld line into account. Therefore, a calculation routine for the prediction of weld line strength in unreinforced plastics parts has been developed at the Institute of Plastics Processing (IKV) in Industry and Skilled Crafts at RWTH Aachen University. In this routine, a reduction factor for the material strength of the weld lines is calculated based on process data generated in injection moulding simulations for use in structural simulations. The calculation is based on a physical model of molecular interdiffusion, which has been empirically expanded and calibrated on the basis of experimentally determined data.