Metal & Powder Injection Mold What type of parts are good candidates for The process of MIM uses Metals Powders, Binders, Mixing, Molding, De-binding, Sintering, Post-sintering operations, and Mechanical properties of MIM components. First we will discuss Metal Powders. For the most part any metal that can be produced in a suitable powder form can be processed by MIM. Aluminum is an exception because the adherent oxide film that is always present on the surface inhibits sintering. A list of the metals that can be used include alloys-plain and low alloy steels, high speed steels, stainless steels, super alloys, intermetallic, magnetic alloys, and hard metals(cemented carbides). Although the most promising materials are the more expensive ones a lot of people still tend to shoot for the more affordable ones that can still get the job done. Particle shape is also important because it is better to incorporate as high a proportion of metal as possible, which means that powders having a high packing density are indicated.
Metal injection molding is a metalworking process where finely-powdered metal is mixed with a measured amount of binder material to comprise a feedstock capable of being handled by plastic processing equipment through a process known as injection mold forming. This allows complex parts to be shaped in a single operation and in high volume. The finished product is used in a range of things from commercial to medical, dental, firearms, aerospace, and even automotive.
The process is pretty complicated. It starts with combining metal powders with wax and plastic binders to produce the feedstock mix which is injected as a liquid into a hollow mold using plastic injection molding machines. The green part is cooled and de-molded in the plastic molding machine. Second a portion of the binder material is removed using solvent, thermal furnaces, catalytic process, or combination of methods. The resulting part in condition called brown stage requires the metal to be condensed in a furnace process called Sintering. These parts are sintered at temperatures nearly high enough to melt the entire metal part, making the metal particle surfaces bind together resulting in a final 99% solid density.