Metal injection molding (MIM) is a molding method in which a plasticized mixture of metal powder and its binder is injected into a mold. It is firstly mixing the selected powder with a binder, then granulating the mixture and then injection molding the desired shape. The polymer imparts its viscous flow characteristics to the mix, which aids uniformity in forming, cavity filling and powder filling. After forming, the binder is removed, and the degreased blank is sintered. Some sintered products may also be subjected to further densification, heat treatment or machining. Sintered products not only have the same complex shape and high precision as those obtained by plastic injection molding, but also have physical, chemical and mechanical properties close to forgings. This process technology is suitable for mass production of small, precise, complex three-dimensional shapes and metal parts with special performance requirements.
MIM technology combines the advantages of powder metallurgy and plastic injection molding, breaking through the limitations of traditional metal powder molding technology on product shape, and using plastic injection molding technology to form parts with complex shapes in large quantities and efficiently It has become a near-net-shape technology for modern manufacturing of high-quality precision parts, and has incomparable advantages over conventional powder metallurgy, machining and precision casting. It produces small metal parts with complex shapes like plastic products, usually weighing 0.1-200g; A variety of complex shapes can be formed like plastic products, such as external grooves, external threads, tapered external surfaces, cross-through holes, blind holes, concave tables, key pins, rib plates, surface knurling, etc.; It has good surface finish and high dimensional accuracy, and the usual tolerance is ±0.3%~0.5%; The material is suitable for a wide range, the product has a high density (up to 95% to 99%), and has a uniform structure and excellent performance; With stable product quality and high production efficiency, it can realize automatic, large-scale and large-scale production.
MIM technology is a very important molding technology in the medical device industry. Small medical devices, precision parts, high-precision parts, and high-performance parts are basically produced using MIM technology. It is also very cost-effective for the production of complex precision parts. Common MIM medical instruments include ear parts, hemostatic forceps, laparoscopes, scalpel handles, dental parts, forceps, scissors, orthopedic joint parts, etc. The current trend in the medical industry is minimally invasive surgery and minimally invasive plastic surgery. Many medical device parts that need to be used are produced by MIM technology. Minimally invasive MIM surgical parts have various geometric shapes and complex structures, which require very high dimensions and accuracy. At present, stainless steel, titanium and nickel-titanium alloys are widely used, and MIM technology is used for dental implants.
The automotive industry has become a major application area for MIM parts, such as numerous MIM auto parts with complex shapes used in engines, gearboxes, turbochargers, locking mechanisms, steering systems and electronic systems. Such as 1) The rocker arm of the BMW engine. One is a rocker arm that rotates with the rollers. This is a rocker arm made of low alloy steel that controls the variable valve timing travel of the engine. It is characterized by its hollow structure and light weight, which is difficult to make by other methods; (2) Shift lever. This is a very high volume MIM custom parts for manual transmissions in passenger cars. The production process of this part is: injection molding, sintering, hardening and assembling the shaft. The material used is Fe2Ni, and the parts should be carburized and quenched after sintering; (3) Turbocharger blades. The production of such MIM variable area nozzle vanes used in automotive diesel turbochargers is high. This part can meet strict dimensional tolerance requirements, and the blade profile can reach an accuracy of ±0.015mm by machining. The blades are produced with special moulds, which have excellent sliding function when opened and reduce deformation when they come out. MIM production can reduce production costs by 20%.
The MIM process has also been widely used in many fields such as smartphones, automobiles, electronic products, mechanical equipment, and consumer goods. Driven by factors such as the rapid growth of electronic products and the substitution of MIM-manufactured parts for traditional process-manufactured parts, the MIM market will still maintain a positive development. A number of key technologies for smart devices represented by smart operating systems, smart human-computer interaction, mobile phone screen display, application processor technology, and battery, charging and other technologies have achieved rapid development, and consumer electronic products such as smart phones and wearable devices are also emerging. into the market. As a typical product with the highest penetration rate, the most diverse forms and the largest demand among the mobile smart terminals, the smartphone plays a rising role as a carrier. The widespread coverage of smart phones continues to influence people's work and lifestyle, and the use of various mobile phone applications and services through the Internet has led to continued deepening of people's reliance on mobile phones. The development trend of thin and light consumer electronic products such as smartphones and wearable devices is accelerating, and the core components of such products are also becoming more sophisticated and complex. In this context, the application prospects of the MIM process are becoming increasingly clear. At present, the process has been widely used in the manufacture of MIM communication parts such as card trays, camera rings, buttons, connector joints, built-in structural parts, watch cases, and buckles.