micro-MIM - micro metal powder injection molding

Modern advanced production techniques are fast moving into the realms of the fantastic. We've regularly marveled at some of the modern advanced production techniques such a 3D printing and now there's a new one - micro metal powder injection molding (micro-MIM). Until now, the production of tiny metal parts using techniques such as etching or milling has been a very complex and time-consuming process, and not suitable for many types of metal. It has been possible for a long time to produce very small parts from stainless steel, but with micro-MIM, it is now possible to combine and shape different types of material such as this (pictured) biocompatible titanium stirrup, a replacement for the small bone in the human ear.

“We make exact copies of this delicate ossicle. Injection molding with very fine metal powder enables us to replicate these tiny structures,” explains Philipp Imgrund of the Fraunhofer Institute for Manufacturing Technology and Applied Materials Research IFAM in Bremen. Now the researchers are in a position to make such small, delicate components out of biocompatible materials such as titanium and titanium alloys.

In a pilot series, the researchers manufactured 300 miniature parts with a weight of 5.4 milligrams each and a wall thickness of only 0.3 millimeters. “We are now ready to start series production with the micro-MIM process,” Imgrund stresses. “Using the stirrup as an example, we are demonstrating the limits and possibilities of the process and of the new materials.” The injection mold for the demonstrator was designed and built by Krämer Engineering in Rendsburg.

Before injection-molding miniature parts, the researchers mix the fine metal powder with an organic binding agent. The mixture can then be processed on an injection molding machine in the same way as a plastic. Following this, the binding agent is expelled from the component, which is then sintered to a high density. “We vary the powder and binding agent and are developing suitable injection-molding and sintering processes. Our objective is to achieve reproducibly high quality for very complex micro-components and to equip these components with additional functions as required,” explains Imgrund. Components could be reinforced with higher-strength material in areas subject to particularly high stress, for example, or a part could be given special magnetic properties.