What exactly is Metal Injection Molding (MIM) process technology?

Metal Injection Molding (MIM) is an advanced manufacturing process that combines plastic injection molding and powder metallurgy technology. It can efficiently produce metal parts with complex shapes, high precision and high performance.

1. Basic process of MIM process
MIM process is mainly divided into the following four core steps:
Feedstock preparation
Raw material mixing: metal powder (particle size is usually 5-10μm) and organic binder (such as wax, plastic) are mixed in proportion to form a uniform “feedstock”.
Binder function: The binder gives the mixture fluidity so that it can flow in the injection molding machine.
Injection molding
Mold filling: The feedstock is heated to the molten state of the binder (about 150-200℃), and injected into the precision mold under high pressure for molding.
Cooling demoulding: After cooling, the “green part” is obtained, which has the same shape as the final part, but contains a large amount of binder.
Degreasing
Removing binder: The binder in the green part is gradually removed by solvent degreasing, thermal degreasing or catalytic degreasing to form a “brown part”.
Key control point: Slow degreasing is required to avoid cracking or deformation of the parts.
Vacuum sintering
High temperature densification: Place the brown blank in a protective atmosphere (such as hydrogen, argon) or a vacuum furnace, and heat it to 70-90% of the metal melting point (such as about 1300℃ for stainless steel), so that the powder particles diffuse and combine, and the final density reaches 95-99% of the theoretical density.
Shrinkage control: After sintering, the parts will shrink evenly (about 15-20%), which needs to be compensated in advance when designing the mold.

2. Core advantages of MIM technology
Complex geometry capability: It can form complex structures such as thin walls, inner cavities, micro-tooth shapes, etc. that cannot be achieved by traditional machining (such as porous filters, precision gears).
High material utilization rate: The material utilization rate exceeds 95%, which is much higher than machining (usually only 30-50%).
Batch and efficient production: It is suitable for large quantities (annual output of more than 20,000 pieces) of small parts with low unit cost.
Material diversity: It supports high-performance metals such as stainless steel (316L, 17-4PH), tool steel, titanium alloy, cemented carbide, magnetic materials, etc.
High precision and surface quality: The dimensional tolerance can reach ±0.3%~±0.5%, the surface roughness Ra 1.2μm, and some parts do not require subsequent processing.

3. Limitations of MIM
Part size limitation: Suitable for small parts weighing 0.1-200 grams and less than 100 mm in size. Oversized parts are prone to deformation.
High mold cost: mold development costs are high and only suitable for mass production to dilute costs.
Long process cycle: degreasing and sintering are time-consuming (total cycle is about 3-7 days).
Material porosity: There are trace pores after sintering, which is not suitable for high-pressure sealing or ultra-high strength scenarios.

4. Key technical parameters of MIM

5. Typical application areas of MIM
Consumer electronics: mobile phone card trays, folding screen hinges, smart watch cases.
Medical devices: surgical instruments, dental brackets, orthopedic implants.
Automotive industry: turbocharger blades, fuel nozzles, seat belt buckles.
Industrial tools: micro gears, drill bits, tool chucks.
Aerospace: drone structural parts, high-temperature resistant alloy parts.

6. Comparison of MIM with other processes

7. Future Trends of MIM
Material Expansion: MIM applications of high-temperature alloys and titanium alloys are accelerating (such as in the aerospace field).
Micron-level precision: MIM technology breakthroughs for micro parts (such as MEMS sensors).
Green Process: Environmentally friendly adhesives and degreasing technology are optimized to reduce energy consumption and pollution.

Summary
Metal Injection Molding (MIM) is the optimal solution for mass production of complex small metal parts, especially for high-precision requirements in consumer electronics, medical devices and other fields. If your parts meet the characteristics of “small size, complex, large quantity, and high material performance”, MIM can significantly reduce the overall cost and improve performance.