Metal Injection Molding FAQ

Manufacturing complex, small metal components can present a challenge to engineers who are limited in scope in terms of their part’s material density, design flexibility, and wall thickness. If you are looking for high quality, complex, precision metal components less than 160 grams, then OptiMIM’s metal injection molding process may be the best course of action.

Metal injection molding, or MIM, is a process that merges two established technologies: plastic injection molding and powdered metallurgy. OptiMIM engineers can create geometrically complex, dense parts that cannot be produced using the conventional powder metal processes without secondary machining. With MIM, it’s possible to integrate and consolidate several components into a single molded piece, freeing designers from the traditional constraints associated with assembling several separately casted parts to achieve a net-shape component.

Our designers know that MIM is not for everyone. With so many metalworking solutions available, it can be difficult to determine when a project can benefit from the MIM process. We have compiled five frequently asked questions to help you decide if MIM is the right process for you.

What materials are used in MIM

MIM materials have had their chemistries modified in order to withstand the complex metal injection molding process. There are a wide variety of materials available for MIM, but we specialize in stainless steel, copper, and low alloy steel materials. We can also process other specialty or custom materials tailored to your mechanical property specifications.  Ask an engineer about our custom feedstock capabilities!

What size parts are most suitable for MIM?

It's also crucial to consider the parting line and parting line witness. Every part has a parting line related to the molding process. However, it's important to be mindful of the application and understand how the parting line's location might affect the part's form, fit, or function. Ideally, the parting line should not be on a functional surface.

What is the porosity of MIM components?

Unlike other casting processes, MIM offers a very high density with uniform, fine grain structure. Typical MIM part density reaches 95-98%, however, some material applications with secondary Hot Isostatic Pressing (HIP) can achieve near wrought material density.

What are the minimum and maximum wall thicknesses that MIM can achieve?

Wall thickness is contingent upon the length of the wall, overall part size, and the part design. If the wall is localized, wall thickness as precise as 0.01” or less is possible. On the other end of the spectrum, wall thickness as large as 0.5” is possible. It is important to note as the wall thickness increases, so does the molding process cycle time, material consumption, and debinding and sintering cycles, which inherently increase total part cost.

How do you accommodate for the shrinkage in the design of the mold?

Over the years, we have studied each material that we use in the MIM process quite extensively. Each alloy and geometry shrinks differently. We developed and use predictive models and factor this into our tooling design.