Customising MIM materials for greater design freedom

Manufacturers' expectations have reached an all-time high. Customers serve consumers who want something more—greater strength and density, more durable products and something unique—tailored specifically for them. How can a metal injection moulding (MIM) business keep pace?

How can the limited design freedom manufacturers faced in the past be overcome? It all comes down to the very foundation of the MIM process—feedstock. OptiMIM aims to manufacture using precisely the right blend of materials to create personalised components that perform to the highest standards.  

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What is feedstock?

What exactly is feedstock? Fundamentally, it is a hybrid technology combining powder metallurgy and plastic injection moulding. Fine, spherical metal powder, almost resembling dust, is mixed with plastic and paraffin wax—or what we call the "binder" system. The binder system gives the part its shape according to your geometry, while the metal powder is carried along in the process.

The final feedstock is approximately 40% binder and 60% metal by volume, with powder particle sizes ranging from 10 to 25 microns. A micron equals one millionth of a metre and, to put this into 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 through our proprietary mixing system and pelletised.

The pellets are then fed into injection moulding machines and moulded to form the first stage of the part – the "green part". Many subsequent processes take place to produce the final net-shape part, but feedstock is the foundation.

Feedstock process control

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

With an emphasis on consistent dimensional control, you can invest the time and resources needed to fully optimise your design for performance without the traditional constraints associated with other processes.

Design freedom with metal injection moulding

Product performance is paramount. Customisation of MIM feedstock enables the design of technology and final parts that cannot be achieved by any other means. Rather than simply selecting a material to suit a part, the ideal combination should be created for optimal performance.

With the ability to produce its own feedstock, OptiMIM solves many complex design challenges. The combination of plastic injection moulding and powder metallurgy gives design engineers freedom from the traditional constraints of shaping stainless steel, nickel iron, copper, titanium and other metals. Unlike other suppliers, engineers are not limited to an off-the-shelf metal that compromises project performance requirements.

Using unsuitable materials in any process can affect part performance. That is why selecting specific material characteristics with a greater degree of fine-tuning delivers better part performance. The proprietary combination of metal, wax and plastic polymers, together with other process controls, enables us to deliver tighter tolerances, high densities and smooth finishes compared with other forms of metal injection, while still producing precise, complex parts in large quantities. Because OptiMIM controls all variables in feedstock development as well as production processes, we deliver tighter 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 approach the MIM process without conventional design constraints. MIM builds component geometry by placing material only where it is 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 usually closer to the original design intent than assembling multiple parts. By consolidating components, risk is reduced, with less potential for part failure.

As all features are engineered into the tooling, part complexity will not drive cost. Conventional design methods, such as deburring or chamfering a stamped part, often result in a higher part price when complexity is added.

MIM dominates at the intersection of complexity, precision, quantity and performance, and it all begins with custom-formulated feedstock. The material you choose must deliver high-performing parts, regardless of component complexity.