The complex manufacturing process of injection molding involves temperature and pressure. Polymer materials experience complex molecular chain deformation behaviors as they undergo temperature and pressure changes. This behavior “history” is retained as invisible stresses inside a finished molded part and may lead to defects or failure. In this lesson you will learn why thermally-induced molded-in stress is an important to understand for molding high quality parts.
Topics in this lesson include: the difference between flow-induced and thermally-induced stress, the factors that affect thermally-induced stresses, how different packing pressure set-ups can affect molded-in stresses, what happens to molecules under tensile and compressive stress, how melt and mold temperature affect packing shear stress and overall volumetric shrinkages, and the impact of various part design features on molded-in stress.