Deflashing of Automotive Formed Parts: Warpage and Tolerance Issues

Blow moulding is one of the most important polymer processing method for producing plastic automotive parts. Yet, there are still several problems that affect the overall success of forming these parts. Among them, are thermally induced stresses, relevant shrinkage and part warpage caused by inappropriate solidification conditions. This work presents a finite element model that allows for predicting residual stresses and subsequent deformations that arise during the cooling stage of finished parts. It is expected that the virtual presence of the flash zone has an influence on the development of residual stresses in the numerical model. Deflashing is usually performed immediately after part removal from the mould, therefore, the numerical model is adapted to take this into account. Numerical results obtained with and without flash for a simple part, as well as a complex automotive part, are compared to determine accuracy and limitations of the model.