Customizing MIM Materials for Greater Design Freedom

Manufacturers' expectations have hit an all-time high. Customers are serving consumers who want something more—better strength and density, more durable products, something unique—tailored just for them. How does a metal injection molding (MIM) business keep up with the times?

How is the limited design freedom that manufacturers faced in the past solved? It all boils down to the very foundation of the MIM process—feedstock. OptiMIM aims to manufacture with just the right blend of materials to create personalized components that perform to the highest standards.  

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What is feedstock?

Now, what exactly is feedstock? At the basis, it's the hybrid technology between powder metallurgy and plastic injection molding. A fine spherical, metal powder, almost resembling dust, is mixed with plastic and paraffin wax—or what we like to call the "binder" system. The intent of the binder system is to give the part its shape to your geometry, while the metal powder goes along for the ride.

The final feedstock is approximately 40% binder and 60% metal by volume, with the size of the powder particles ranging from 10 to 25 microns. A micron is equal to one millionth of a meter, and to put that in perspective, 40 microns is the smallest particle visible to the human eye. Did you know that the average human hair is 100 microns wide? All three materials are mixed together, extruded from our proprietary mixing system, and pelletized.

The pellets, in turn, are fed into the injection molding machines, and formed into the first stage of the part – the "green part". Many other processes happen downstream to produce the final net-shaped part, but feedstock is the understructure.

Feedstock Process Control

Custom formulating alloys adds a layer of complexity to the process. It's critical for suppliers to have a sound, uniform, and repeatable mixture of feedstock for optimal consistency of mechanical performance and properties. The knowledge and expertise of the metallurgists must be precise, with very tight controls in place, when incorporating multiple materials in the feedstock. Consistent dimensional controls are needed not only from part to part, but from batch to batch. It is what allows OptiMIM to have predictable and repeatable shrinkage of our components during the sintering phase each and every time.

With an emphasis on consistent dimensional control, you are able to spend the time and investment needed to fully optimize your design for performance without the traditional restraints associated with other processes.

Design Freedom with Metal Injection Molding

Product performance is paramount. The customization of MIM feedstock allows for the design of technology and final parts that cannot be delivered by any other means. Instead of simply picking a material to fit a part, the perfect fusion should be created for optimal performance.

With the ability to produce its own feedstock, OptiMIM solves a lot of complex design problems. The combination of plastic injection molding and powdered metallurgy allows design engineers freedom from the traditional constraints of trying to shape stainless steel, nickel iron, copper, titanium, and other metals. And unlike other suppliers, engineers are not stuck with an off-the-shelf metal that compromises project performance requirements.

Using the wrong materials in any process can impact the part performance. That's why selecting particular material characteristics with a tighter degree of fine-tuning, delivers better part performance. The proprietary combination of metal, wax, and plastic polymers, along with other process controls, allows us to deliver tighter tolerances, high densities and smooth finishes compared to other forms of metal injection, and while still producing precise, complex parts in large quantities. Since OptiMIM controls all variables of the feedstock development, as well as production processes, we deliver higher tolerance control from part-to-part and batch-to-batch with higher capability. This vertical integration gives us a unique advantage in the MIM industry.

Designing Metal Parts for Performance

Design engineers can look at the MIM process as a clean slate. MIM builds component geometry by placing material only where it's needed for function and strength. Multiple components can be combined into a single MIM component, and the resulting geometry is stronger, more cost effective, and is usually closer to the original design intent than assembling multiple parts. By consolidating components, risk is mitigated with less potential for part failure.

Since all features will be engineered into the tooling, part complexity will not drive cost. Conventional methods of designing, like deburring or chamfering on a stamped part, often equate to higher part price when adding complexity.

MIM dominates at the intersection of complexity, precision, quantity and performance, and it all begins with custom-formulated feedstock. The material you choose needs to deliver high-performing parts, no matter how complex the component.