Metal Injection Molding: A Key Process for Achieving High Precision in Small Parts

In the field of precision manufacturing, the precision requirements for small parts such as micro gears, medical implant components, and electronic connectors often reach the 0.01 mm level. Traditional processing techniques often fall into the dilemma of "difficult to form and difficult to control precision." Metal injection molding (MIM), with its dual control over the structure and precision of small parts, has become a key process to overcome this bottleneck, providing core support for high-end manufacturing.

MIM's adaptability to small parts begins with the precise matching of materials and molding processes. Small parts typically have complex structures, such as micro-holes, thin walls, and toothed features. MIM uses a feedstock made by mixing 5-20 micrometer ultrafine metal powder with a binder. Its flowability is comparable to plastic, allowing it to fill tiny mold cavities under high pressure. Compared to the clamping deformation that CNC cutting can easily cause to small parts, MIM's "one-step molding" mode can completely replicate complex structures, achieving an initial blank precision of ±0.5%, laying the foundation for subsequent precision improvements.

The core of precision control lies in the meticulous control of details throughout the entire process. In the materials stage, powder particle size deviation is controlled within 2 micrometers, and binder ratio error does not exceed 0.5%, avoiding molding defects caused by uneven composition. During injection molding, mold cavity precision reaches 0.005 millimeters, coupled with precise temperature control of 150-200℃ and gradient pressure adjustment of 10-100MPa to prevent shrinkage cavities and flash in small parts. During debinding and sintering, a step-by-step debinding technique is used to control the heating rate, with sintering furnace temperature fluctuations not exceeding ±5℃. Simultaneously, a preset shrinkage rate parameter of 15%-25% precisely matches the final dimensional requirements.

In practical applications, the precision advantages of MIM are fully demonstrated. A consumer electronics company's miniature transmission gear, with a diameter of only 3 mm and containing 12 precision tooth grooves, achieved a tooth profile tolerance within 0.008 mm and a pass rate of 99.2% after adopting MIM (Metal Injection Molding) technology, far exceeding the 90% pass rate of traditional stamping processes. In the medical field, orthopedic miniature bone screws require thread precision of ISO 4H grade. MIM, through powder selection and sintering curve optimization, achieves dual compliance with thread profile integrity and surface roughness standards, meeting the stringent standards for implantation in the human body.

Precision stability in mass production is another outstanding advantage of MIM. The demand for small parts is often in the millions. MIM, through standardized molds and automated production lines, can achieve a daily production of over 5,000 pieces per mold, with batch-to-batch dimensional deviations not exceeding 0.003 mm. This characteristic allows it to ensure precision while reducing costs in the mass production of precision parts such as 5G base station RF components and automotive sensors.

Precise control across the entire chain, from materials to processes, makes MIM the "optimal solution" for high-precision manufacturing of small parts. With the upgrading of powder metallurgy and temperature control technologies, this process is driving breakthroughs in miniature precision parts towards becoming "smaller, more precise, and cheaper".