Designing for Manufacturing using Plastic Injection Molding

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Design for Manufacturing (DFM) is a crucial aspect of the plastic injection molding process. It involves optimizing the design of a plastic part to ensure that it can be easily and cost-effectively manufactured using injection molding techniques. Here are some key considerations and guidelines for DFM in plastic injection molding:

Part Geometry and Complexity:

  • Keep the part geometry simple and avoid intricate features that could complicate the molding process or require complex tooling.
  • Minimize the use of undercuts, sharp corners, and thin walls to prevent molding defects and challenges in ejection.

Draft Angle:

  • Incorporate draft angles (tapered surfaces) on vertical walls to facilitate easy ejection of the part from the mold.
  • A typical draft angle is around 1-2 degrees per side, but this may vary based on the material and part design.

Wall Thickness:

  • Maintain uniform wall thickness throughout the part to ensure proper flow of molten plastic and reduce the risk of sink marks, warping, or voids.
  • Avoid sudden transitions between thick and thin sections, as this can lead to molding defects.

Ribs and Bosses:

  • Use ribs to reinforce thin sections of the part and add structural integrity.
  • Design bosses (protruding features) with appropriate wall thickness and draft angles to ensure good mold filling and easy part ejection.

Corners and Fillets:

  • Incorporate rounded corners and generous fillet radii to distribute stress and prevent stress concentrations that could lead to part failure.

Material Selection:

  • Choose a suitable plastic material for the intended application, considering factors such as mechanical properties, chemical resistance, temperature stability, and more.

Gating and Venting:

  • Position the gate (entry point for molten plastic) in a location that minimizes aesthetic defects and ensures uniform filling.
  • Provide adequate venting to allow air and gases to escape during injection, preventing voids and trapped air.

Texture and Surface Finish:

  • Consider the desired texture or surface finish early in the design process, as this may impact mold design and material flow.
  • Textures can help hide imperfections and improve aesthetics.


  • Specify realistic tolerances that are achievable through the injection molding process.
  • Avoid tight tolerances that could increase manufacturing costs and lead to rejects.

Moldability Analysis:

  • Conduct mold flow analysis using simulation software to identify potential issues and optimize the part design before production.
  • Address potential concerns such as weld lines, air traps, and flow imbalances.

Tooling Considerations:

  • Collaborate closely with the tooling manufacturer to ensure the mold design aligns with the part design and material properties.
  • Optimize the number and complexity of mold cavities based on production volume requirements.

Assembly and Post-Processing:

  • Design parts for easy assembly by incorporating features like snap fits, self-locating tabs, and mating surfaces.
  • Minimize the need for secondary operations or post-processing steps.

By following these design principles and collaborating with experienced injection molding professionals like Performance Plastics, you can create plastic parts that are well-suited for efficient and cost-effective manufacturing through the injection molding process.

For more information on Design for Manufacturing and its use, please contact Rich Reed, Vice President of Sales & Marketing at [email protected], or visit our website at www.performanceplastics.c