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Lesson 3: Understanding Thermally-Induced Molded-In Stress

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.

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Understanding Thermally-Induced Molded-In Stress

Learn the fundamentals of process optimization by understanding how different phases in the injection molding cycle will influence the overall part quality. Build your own Circle of Knowledge lesson by lesson. 

Goals of Processing: Shrinkage and Warpage (Level 1): 

  • Learn the fundamentals of shrinkage and warpage during the processing phase of injection molding
  • Gain an understanding of how part design, mold design, and process are connected and interdependent
  • Analyze real-life molded parts and learn the cause and effect behaviors of design and process

Section Description: 

Molding high-quality parts is dependent on many factors, including skillful part and mold design, an understanding of polymer material behavior, and an optimized process. It is important for injection molding processing engineers to follow key steps to ensure consistently high-quality molded parts.

Explanations, simulations, cause and effect analyses, and specific shrinkage and warpage examples are covered in this section.

Recommended For: Entry Level Personnel, All Personnel

Length: Lessons are approximately 15-20 minutes long each

The Kruse Training platform delivers knowledge and expertise developed over two decades in the plastic injection molding industry. Now companies and individuals can access a state-of-the-art online training program, suited for all levels of knowledge.