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Lesson 2: Packing Pressure Profiles: Semi-Crystalline Materials

One of the key steps in the injection molding process is the packing and holding phase, sometimes also referred to as the compensation phase. In this lesson the term packing phase will be used to describe the full process step. During the packing phase material is continuously “packed” into a cavity, thereby compensating for the shrinkage that occurs due to material cooling inside the mold. Processors can optimize a packing profile by understanding the material characteristics of the polymer to be molded. In this lesson we will focus on packing profiles of semi-crystalline materials.

This lesson reviews the internal structure of semi-crystalline materials, risks of over- or under-packing a part, pack pressure and how it relates to volumetric shrinkages, clamp tonnages, and cavity pressure, and how to optimize a packing pressure profile using a semi-crystalline polymer.


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Semi-Crystalline Packing Pressure Profiles

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: Packing and Cooling Phase (Level 1): 

  • Learn the fundamentals of process optimization by analyzing the packing and cooling phase of molding a part
  • 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 various packing and cool phase variables 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.