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Comparing Metal Injection Molding & Powdered Metallurgy

Manufacturers around the globe are always looking to create better-performing metal components. They want more design freedom without sacrificing cost. When traditional methods of casting no longer make the cut, manufacturers are turning to other molding processes to drive their products forward.

If you are familiar with powdered metallurgy (PM), you know the parts are formed from metal that is pressed together in a die and then sintered. Metal injection molding (MIM) is a complementary process that also uses metal particles—just much finer— to produce high-density components with three-dimensional design flexibility.

Learn more about the MIM manufacturing process here >>>

Where MIM Differs

Materials

PM and MIM utilize the same base powders and both processes allow for the use of custom alloys, however, the key difference in material is particle size. Coarser powders used in PM are widely known and the route to make them are inexpensive. MIM powders are much smaller so the process and energy to make them—in that size range—are more expensive to produce.

The cost of the powdered metal is a key driver when comparing MIM and PM materials. MIM powders are typically more expensive than PM powders since they are finer (-20 micron vs. +100 micron). However, because of the finer material, MIM produces significantly less porosity.

Did you know? PM achieves all density in the compacting stage (85-92% density) while MIM density comes from sintering—a diffusion bond. (95%+ density)

Design Freedom

Engineers often confuse MIM and conventional PM given that the two start with powdered metal. PM relies on a high-pressure uniaxial compaction. PM is more suitable for simple shapes that are easily ejected from the die cavity. This is where MIM differs. With MIM, there are very few—if any—geometrical restrictions allowing for three-dimensional design freedom.

 Other design improvements for MIM components include:

  • Part consolidation
  • Uniform wall thickness
  • Coring and mass reduction
  • Holes and slots
  • Undercuts
  • Threads
  • Knurling, letter, and logos

Powdered Metallugry Metal Injection Molding
50-100pm Powdered Particle Size 2-15pm
92% (Max) Relative Density >95-99%
2-20mm Wall Thickness 0.30 -10mm
Medium Component Complexity High
1-1,000g Weight 0.01-200g
0.1-2.0% Tolerance 0.3-0.5%

Physical Properties

While the MIM and PM processes may seem similar, the major differences are found in the final properties of the finished component—mainly the final density. When you use the PM process, the friction between the powder and tooling make the final component non-uniform, while MIM parts are uniform in all directions.

Additionally, sintering for MIM takes place at much higher temperatures than PM (2350-2500F° vs. 1800-2000F°). The larger PM metal powders combined with lower sintering temperatures inherently cause the final PM component to have lower physical properties making MIM components about two times stronger, with significantly better toughness and fatigue strength. 

MIM PM
Elongation High Low
Hardness High Low
Surface Finish High Medium
Production Volumes High High
Range of Materials High High
Cost Medium Low

Where Does MIM Fit?


Where you add cost for more expensive feedstock and tooling, you realize the savings when it comes to high-density, high-complexity components that cannot be made by any other manufacturing process. PM may be a cost-effective alternative for simple parts but MIM can produce part geometries that eliminate secondary operations which can result in significant cost savings.

Many of our customers find substantial savings when they combine two or more subcomponents into one single MIM component. Additional savings are found when you consider materials, design, assembly and logistic benefits to the MIM process.

Illustrated in the graph below, there is a certain degree of complexity and volume that must be considered to make MIM the more economical manufacturing choice.

Metal Injection Molding versus other production processes

Leading Metal Injection Molding Manufacturer

On every project, we aim to deliver more consistent parts, more efficiently, at lower costs. Our goal is to do away with the expenses associated with secondary processes such as machining, achieving net-shape the first time.

So we build molds that are more efficient for high-volume production and put in as much complexity as needed up front to avoid costly machining and secondary operations.

Contact our team today to get the conversation started. 

 

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Last updated 04.02.2020