With so many metalworking solutions out there, we often have engineers ask, “What is MIM and when should I use it?” If you are not familiar with Metal Injection Molding (MIM), it combines the technologies of thermoplastic injection molding and powder metallurgy to produce complex shaped, high density, high-performance metal parts. If you have exhausted all other options and your part is still failing, MIM may be a good fit.
Utilizing the Metal Injection Molding Process
A OptiMIM customer needed to create a surgical part for minimally invasive surgery. They had tried every other option before landing on MIM. Machining and laser sintering were too expensive. There were too many tight tolerances and the part was not structurally sound for conventional die casting. Plastic injection molding wasn’t strong enough so they tried stamping a 2D part but the secondary operations that were needed made the part too expensive for a one-time use during surgery. OptiMIM provided a MIM solution with a stronger part that met all medical requirements and was much more cost effective. Compared to machining MIM saved this customer over $100 USD per part.
MIM is best applied to small parts (typically less than 100 grams) that are often complex in nature. The maximum section thickness is generally kept to less than 0.25 inch and tolerances are typically +/-0.3 percent down to +/-0.001 inches. The MIM process favors higher annual part volumes—typically 10,000 parts or more as this technology is a batch-drive process. Materials applied in the MIM process include many ASTM type alloys including various ferrous and non-ferrous alloys, titanium, copper, and nickel just as some examples. With our in-house capability producing our own feedstock, OptiMIM has also created custom materials that might offer you unique mechanical properties not associated with available ASTM materials on the market today.
Since the commercial beginnings of the Metal Injection Molding process in the mid-1970s, the technology has matured and gained acceptance in numerous industries, including:
- Medical and dental instruments
- Lock components
- Computer and electrical applications
- Aerospace and military applications
The Benefits of MIM
While there are a variety of benefits in the MIM process, engineers usually realize the positives after they have tried every other process and failed. The benefits of the Metal Injection Molding process are best realized by considering the MIM manufacturing process during the initial design stage of the parts or assembly. Other primary benefits of MIM include:
- Improved properties - MIM parts are typically 95% to 98% dense, approaching wrought material properties. MIM parts achieve greater strength, better corrosion resistance, and improved magnetic properties when compared to conventional powder metallurgy processes.
- Design freedom - MIM offers design flexibility similar to plastic injection molding. Geometrically complex parts that cannot be produced using the conventional powder metal processes without secondary machining are possible using the MIM process.
- Enhanced details - MIM provides intricate features such as dovetails, slots, undercuts, internal and external threads, and complex curved surfaces. MIM can produce cylindrical parts with greater length-to-diameter ratios.
- Reduced assemblies – The MIM process can be used to combine two or more simpler shapes into a single, more complex component to minimize assembly costs.
MIM Offers Design & Cost Solutions
The MIM process offers lower cost solutions for numerous applications compared to machining or investment casting, and it has improved mechanical properties compared to plastic injection molding and even zinc die casting. MIM materials are typically stronger than die casting alloys, corrosion resistant, and magnetic. MIM replaces die casting when draft angles are not allowed or higher wear requirements are needed. So, if you have a small, complex part that requires higher strength requirements and you want to produce large quantities, your project may very well benefit from the design freedom and cost solutions that MIM provides. If you are interested in learning more, we suggest you contact one of our design engineers who can walk you through the MIM process and its benefits.