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Metal Injection Molding: Design 101

Metal injection molding (MIM) provides engineers with the ability to produce complex, compact, and lightweight components for a multitude of industries. During the metal injection molding design process, there are several factors you need to look at, including:

  1. Orientation
  2. Gate Positioning
  3. Witness Marks
  4. Surface
  5. Draft Angles
  6. Sag Effect
  7. Wall Thickness
  8. Surface Area
  9. Corner Breaks & Fillets
  10. Holes & Slots

In order to start you on your MIM journey, we’ve provided a brief overview of the main design criteria needed to manufacture parts that meet/exceed quality requirements.

Metal Injection Molding Design Guide

  1. Part orientation: For more efficient part removal, you should orient features perpendicular to the parting line.

  2. Gate positioning: You should locate gates so they direct the flow onto a core pin or cavity wall. In parts with varied wall thickness, position gates so the material flows from the thicker to thinner sections.

  3. Witness marks: MIM components often have witness marks, which are marks from parting lines, gates, and ejector pins. When designing a MIM part, keep the location of witnesses in mind. You can control that by designing it so it's depressed down and you don't have anything standing up on the surface.

  4. Surface: MIM parts are often placed on flat setters for sintering so parts with long cantilevers and spans need additional support from ribs or custom fixtures. Including a flat surface in your part design can eliminate the need for custom fixtures and also minimize the cost of the fixture. 
  5. Draft angles: To reduce the amount of drag, apply a degree of draft (tapering) to the faces of your component. 
  6. Sag effect: During the sintering process, the temperature is just below the melting point of the metal, where the bonding of particles happens. Incorporating support features into your design is essential to prevent troublesome sag or droop. 
  7. Wall thickness: To ensure the process of filling the material runs smoothly, you should design your MIM part to have uniform wall thickness.
  8. Surface area: To allow the use of standard or flat debinding and sintering plates or trays and eliminate the need for custom debinding and sintering supports, you should design your MIM component with a large flat surface or with several features that share a common plane.
  9. Corner breaks & fillets: One of the technical advantages of MIM is producing corner breaks and fillets. Incorporating these design features provide engineers with design advantages, such as: 
    • Improved part strength
    • Softening of sharp corners for handling/aesthetics
    • Helps create a more robust tool, minimizing maintenance
  10. Holes & slots: You can easily produce holes and slots with the MIM process, though adding such features increases the cost and complexity of the mold. Not only can holes and slots add functional features to your component, they can also be used to provide uniform wall thickness and reduce part mass. 

Ready to Design?

When designing a MIM part, you need to keep a variety of factors in mind, including surface features, shrinkage during sintering, part orientation, material properties, and much more. If you’re new to the MIM design process, it’s best to consult with an expert to understand the implications of what you’re adding to the geometry and how that’s impacting the part. 

Ready to learn more? Check out our other resources on all things metal injection molding and metal additive manufacturing.