Systematic reduction of size deviations between injected and designed products and effects of process parameters on warpage

In plastic Injection Molding (IM), dimensional deviations such as shrinkage and warpage are common causes of product malfunction. Product quality is strongly governed by both geometric design and injection process parameters (IPPs). This study presents a systematic approach to address the warpage problem of a thick-walled, tubular-shaped housing cap used to regulate water intake and discharge between filters in a water purifier. The study had two objectives. First, the leakage problem of the component was resolved through a systematic design method in which candidate conceptual designs were evaluated against defined criteria. In evaluation, Analytic Hierarchy Process (AHP) was applied to make the aggregation fully objective. Second, the optimum IPP values yielding the lowest warpage for the selected design concept were identified using the Taguchi experimental design method. The results demonstrate that the leakage problem was eliminated by reducing warpage by 70%. The proposed approach shows promise for corresponding warpage problems in the IM of geometrically complex, thick-walled components; since it was validated on a single POM housing-cap geometry, its generalizability to other materials and part geometries may be approved through further case studies.