Metal Injection Molding (MIM) processing technology has a history of nearly 40 years, and is currently becoming a hot topic in the metal parts manufacturing industry. Generally, the weight of MIM workpieces is less than 250 grams, and the size of most MIM workpieces is about the same as a folding mobile phone. However, larger MIM workpieces are now increasing.
If the batch size of workpieces to be produced is large (e.g., from 20,000 to several million), and the workpieces have complex geometries (e.g., 20 to 30 measurable dimensions), and require more than three processing steps, then MIM technology processing is a viable option. Some workpieces that can be processed with MIM technology include: computer hard disk drives and other peripheral equipment parts, hand tool parts, firearms parts, liquid syringe and sprayer parts, medical equipment parts, and cutting tools.
MIM technology processing includes the following steps:
(1) Injecting a mixture of powdered metal and thermoplastic (or other binder) into a mold cavity under heating and pressure (similar to plastic injection molding).
(2) Removing the binder by heating or melting, leaving only the metal powder.
(3) Sintering the metal powder. The sintering temperature should be lower than the melting point of the metal, but high enough to combine the metal powder into solid metal (the actual density of the solid metal is greater than 96%).
MIM technology is used for cemented carbide, iron-base alloy and metal alloys (including precious metals). Since the particle size of metal raw materials used in MIM technology is much smaller than the metal particles used in other powder metallurgy processes, it is more appropriate to call it metal “micro powder”, and its fineness is equivalent to that of metallic pigment powder (particle size less than 20μm).