What is MIM (Metal Injection Molding)?
Metal Injection Molding (MIM) is a novel near-net-shape technology that integrates modern plastic injection molding with powder metallurgy.
Plastic injection molding, known for its low cost, is widely used in various industries, primarily for manufacturing complex-shaped products. However, traditional plastic
products often lack strength. To enhance strength and wear resistance, researchers began incorporating metal or ceramic powders into plastics. By maximizing the solid
particle content and removing binders entirely during the sintering process, this new powder metallurgy forming technique became known as Metal Injection Molding (MIM).
Key Processes in MIM
a).Specialized Feedstock
Approximately 90% metal powder is mixed with 10% binder to form homogeneous feedstock. Compared to traditional powder metallurgy, the fine particle size and low impurity content of MIM
metal powders ensure sintered density reaches 98% of theoretical density. Specialized binders not only offer excellent flow during injection but also ensure efficient debinding.
b).Precision Injection Molding
The feedstock is heated and injected into a mold cavity using an injection molding machine. After cooling, a MIM green part is formed. Designing molds suited for MIM and optimizing the
process are critical at this stage.
c).Debinding
Using a specialized debinding furnace, the primary binder is gradually and efficiently removed, leaving a residual skeleton binder to maintain the product's shape. This ensures stability during the
subsequent sintering process.
d).Sintering
In a vacuum or atmosphere furnace, the skeleton binder is removed, and metal powders densify near their melting point to form a complete metallic structure. The cooled part closely resembles
the final product in shape and dimensions.
e).Post-Processing
Surface treatments or machining processes, such as sandblasting, polishing, cleaning, PVD coating, threading, and CNC machining, are applied as required to enhance appearance or functionality.
Advantages of MIM
a).Higher Economic Efficiency
For complex components, traditional metal forming often involves producing and assembling individual parts, while MIM achieves this through integrated processing, simplifying procedures and
lowering costs.
In traditional methods, production costs increase with part complexity, whereas MIM maintains stable costs by leveraging mold complexity, making it particularly economical for intricate designs.
b).Capability to Produce Complex Parts
MIM can manufacture highly intricate components, utilizing structures achievable through injection molding.
It surpasses traditional investment casting in producing features like small holes, thin walls, and fine surfaces.
c).Wide Range of Material Choices
MIM is compatible with most metallic materials, making it suitable for applications demanding high material performance.
d).High Density and Excellent Properties
MIM products achieve sintered densities close to theoretical values, resulting in superior physical and mechanical properties, such as exceptional strength, compared to
traditional powder
metallurgy.
5.High Dimensional Accuracy
MIM typically achieves dimensional tolerances within 0.8%. Further precision can be achieved with additional machining processes.
6.High Production Scalability
MIM allows flexible production scaling, from hundreds of parts per day to tens of thousands, enabling rapid response to market demands.
Applications of MIM
MIM products are widely used across various industries, with immense market potential. Key application areas include:
Computers and Accessories: Printer components, magnetic cores, striker pins, drive parts.
a).Tools: Gun drills, drill chucks, power tool and hand tool parts, wrench components, milling heads, nozzles.
b).Household Appliances: Watch cases, watch bands, electric toothbrushes, scissors, fans, golf club heads, imitation jewelry, knife blades.
c). Medical Devices: Orthodontic brackets, surgical scissors, tweezers.
d). Military Equipment: Missile fins, gun components, bullets, shaped charge liners, fuse components.
e). Electrical Components: Micro motor parts, electronic components, sensors, mobile phone parts, pager parts.
f). Machinery Components: Small, complex parts for cotton pickers, textile machines, sewing machines, office machinery.
g). Automotive and Marine Components: Clutch rings, rocker arm inserts, shift fork sleeves, distributor sleeves, airbag parts, automotive locks.
h). Oil and Drilling: Special-shaped hard alloy nozzles and other components.
With its exceptional economic efficiency, capability to handle complex designs, and superior material performance, MIM technology is becoming a key solution for
manufacturing complex parts.