About Metal Injection Molding

MIM is a process that merges two established technologies: plastic injection molding and powdered metallurgy. It offers a manufacturing capability of producing precise, complex parts in large quantities.

MIM Materials

There are a wide variety of metal alloys available for the MIM process including different types of steel, titanium, and copper—to name a few. OptiMIM specializes in:

Stainless steel – ideal for applications requiring strength, ductility, and corrosion resistance

Low alloy steel – generally used for structural applications especially when high strength and hardness are necessary

Copper– most commonly used for thermal management applications that require miniaturization, improved heat transfer, and electrical conductivity

Metal Injection Molding Process

Once the proper material is selected, the key steps for the MIM process are as follows:

Step 1: Feedstock – Very fine metal powders are combined with thermoplastic and wax binders in a precise recipe. A proprietary compounding process creates a homogenous pelletized feedstock that can be injection molded just like plastic. This achieves ultra-high density and close tolerances over high-production runs. 

Step 2:  Molding – The feedstock is heated and injected into a mold cavity under high pressure, allowing for extremely complex shapes. Once the component is removed it is known as a "green part."

Step 3: Debinding – the “green part” is then put through a controlled process called debinding that removes the binder and prepares the part for the final step. Once the debinding is complete, the component is referred to as “brown.”

Step 4: Sintering – the “brown” part is held together by a small amount of binder and is still fragile. During sintering temperatures reach near the melting point of the material. Sintering eliminates the remaining binder and gives the part its final density and strength. 

MIM Tooling

When choosing a MIM manufacturer you want to make sure that whatever tooling process you choose delivers consistent parts efficiently and repeatedly. Our conventional tooling process is designed to offer you efficiency in production and lower costs.

Wondering if your part is a good size for MIM? Read more here. 

Heat Treating for MIM Components

MIM materials may be heat treated to increase strength, hardness, and wear resistance. The degree of hardening is determined by the percentage of carbon, alloying elements, and residual porosity of the component. Heat treating allows you to achieve ultimate properties for the alloy. To ensure optimum strength and durability, tempering or stress relief is required after quenching.

Other Secondary Operations after Sintering

After your components are completely rid of all binding material, OptiMIM offers many secondary operations to improve dimensional control, including:

• Coining
• Sizing
• Straightening
• Machining (miling, turning, grinding, etc.)

During the sintering process, parts can be distorted, and start to sag or drag. The processes above correct these issues and return the part to its original design. 

Benefits of MIM

MIM offers greater design freedom than many other production processes by freeing designers from the traditional constraints associated with trying to shape stainless steel, copper, titanium, and other metals. Other benefits of MIM, include:

• MIM makes it possible to integrate and consolidate several components into a single molded piece—reducing the need to work with several manufacturers and decreasing processing and assembly costs.
• Texture, knurling, threads, lettering, and company logos can all be incorporated into the mold.

Design for MIM

Design for MIM manufacturability is one of the most important steps that can be overlooked. When you design for MIM there are a number of factors that you can plan for that reduce or eliminate the need for secondary operations after sintering—which can increase overall component cost. Ask your design engineer about sintering supports, draft, fillets and radii, as well as sink and knitlines and what they plan to do to prevent part distortion.

Global MIM Manufacturer

Our team of engineers offer design solutions for a variety of industries including consumer electronics, automotive, healthcare, and more. When our engineers are involved early in the project, they can help design a tool and part specifically for mass production. We can also aid in combining multiple components to create one, cost-effective, and functional part. All of our customers receive insight and expertise throughout all stages of the project. Contact our engineering team to request a quote today.