Design for Injection Molding: Using Process Simulation to Assess Tolerance Feasibility

Abstract

Abstract This paper proposes an effective use of process simulation in the dimensional tolerancing of injection molded thermoplastic components. The complexities of the injection molding process make it difficult for designers to assign dimensional tolerances. No standard method exists for predicting the feasibility of a design tolerance. Advances in injection molding simulation software offer information that could aid in tolerancing. However, engineers have not effectively used these programs for tolerancing. This paper proposes a methodology for using process simulation in evaluating the feasibility of a tolerance scheme. The methodology entails using simulation to quantify the dimensional errors due to process variations and estimate sensitivities. Comparison of simulation results with tolerances specified by designers helps them evaluate whether the desired tolerances are feasible. The paper describes the steps required for estimating the dimensional errors and defines criticality as a measure of tolerance feasibility. A plastic housing for an electrical switch serves as an illustrative example.