Welcome Guest!

Select Level

Lesson 3: Entrapments

The injection molding process is a complex 3-dimensional polymer flow and transient heat exchange manufacturing process. Part design, mold design, and the molding process are all intrinsic to a successful outcome. This lesson focuses on gas and air entrapments, a common molding defect that can create numerous issues including burn marks, short shots, and blemishes in molded parts. Optimizing part geometry and mold design is essential for avoiding entrapments.

Topics in this lesson include: the causes and possible solutions for entrapment during the filling process; how race tracking and hesitations can cause entrapments; how internal venting may be a solution for entrapment conditions; and how wall thickness variations can cause entrapments.

You are not signed up for this course. Subscribe here!


Learn about the causes of common molding defects and how to prevent them. Continue to build your own Circle of Knowledge lesson by lesson. 

Goals of Molding Defects (Level 2): 

  • Learn about the various molding defects that can occur during the injection molding process
  • Gain an understanding of how part design, mold design, and process impact molding defects
  • Analyze real-life molded parts and learn the cause and effect behaviors of design and process

Section Description: 

Molding defects in injection-molded parts range from minor surface defects to major structural issues that significantly impact overall part quality. This section shows you common molding defects, how and why the occur, and ways to minimize or prevent them.

NEW FOR LEVEL 2 MOLDING DEFECTS LESSONS: Each lesson has multiple samples of the molding defect using interactive 3D parts. The examples allow the user to manipulate the simulated part to gain a clear and concise understanding of how each molding defect would appear on a real-life injection molded part.

Video explanations, interactive 3D molding defect examples, simulations, and cause and effect analyses are covered in this section.

Recommended For: Mid-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.