Study on residual stress effects to cracking in the injection molding product—a case study of CPVC male threaded adapter fittings with copper insert

Metal/alloy insert threaded polymer fittings are currently being widely used due to their outstanding advantages due to the combination of mechanical properties between polymers and metals/alloys. However, research and literature on metal insert thread adapter fittings are still limited nowadays. This study focuses on chlorinated polyvinyl chloride (CPVC) male threaded adapters with copper insert and their cracking for the purpose of conducting an insert threaded fitting literature. Crackings are generated by residual stresses accumulating internally over time, unobservable immediately after creating products. This study has discovered cracking by experiment and reduced residual stress by optimizing process parameters via the Taguchi method and mold–insert temperature survey, based on the Moldex3D simulation model. Furthermore, dimensional accuracy is ensured through the warpage displacement assessment. These methods could assist manufacturers in getting pilot-run samples to determine the suitable process parameters, ensuring the longevity of CPVC male threaded adapters with copper insert in particular and piping systems in general.