Modelling of an Analytical Equation for Predicting Maximum Stress in an Injections Moulded Undercut Geometry during Ejection

摘要

The paper presents procedure for analytical assessment of maximum stress in an injection moulded undercut geometry during ejection. Incorrect geometry definition can lead to permanent deformation of a part after ejection. Comparison of maximum stress with the mechanical properties of a material can be used for predicting permanent deformation and for designing of a tool. Investigation of stress-strain behaviour in apart made from thermoplastic polymer during ejection was carried out using experimental and numerical finite element analysis approach. A Taguchi Design of Experiments was used to reduce the number of necessary numerical analysis. The results were used to model analytical equations, for assessing the maximum stress in a part during ejection, taking into consideration height h, fillet radiuses R-1,R-2 and the draft angle beta. An artificial neural network model and models with different combinations of first order, second order, and exponential terms were evaluated to find the best fit. Verification of the analytical equations was done by determining the optimum values using a global optimization approach. The advantage of such procedure is time effective assessment of maximum stress in an injection moulded undercut geometry during ejection with analytical equation instead of a using time-consuming and complex finite element approach.