Application of Metal Injection Molding (MIM) in the Medical Field

Metal Injection Molding (MIM) was developed in 1972 by a small company in Petaluk, California, USA. It was first used in the medical industry in the early 1980s to produce some orthodontic appliances. The MIM method is low-cost and flexible in design. It can produce small and complex parts, which is better than machining or precision casting. MIM dental orthopedic parts also have good biocompatibility and corrosion resistance. Before 1990, there were at least four MIM production companies in the United States.

In the early 1990s, the demand for various new surgical devices with minimal human damage increased significantly. The MIM industry targeted new markets and successfully converted many parts into MIM processing or design into MIM parts. It also produced a large number of live dissection forceps installed on laparoscopes to extract live specimens, cut or suture. The MIM parts of the endoscopic surgical stapler produced by Advanced Molding Technology won the Excellent Molding Award in 1997. The gears of the shear center of laparoscopic surgery produced by Flomet won all awards in 1998. The demand for small and more complex medical devices continues to grow. Nearly 4 In recent years, the Metal Injection Molding Association has identified the medical industry as one of the three major growth points of the MIM market. Most of this growth comes from laparoscopic devices, pacemakers, valves, and many parts used in cardiac surgery. Extracorporeal circulation heart surgery also requires MIM parts. Parts for ophthalmic surgery devices and other special devices are also being developed. In addition, many new devices are designed with MIM parts. Therefore, the application of MIM will be popularized in the United States and promoted to all parts of the world.

New materials may play an important role in the growth of MIM in the medical industry in the future. One of the main medical markets for small and complex parts is implants. Since MIM cannot produce medical-grade titanium materials at present, it is difficult for the market to accept MIM titanium as implants. There are many titanium MIM parts, but the grain size and oxygen content have not been reduced to the level required for implant applications. There are only cobalt-chromium alloys on the market. Now there are also F-75 alloy implants. It is reported that Thermal Technology has made significant progress in the production of titanium products. The performance data of the materials they produce does not meet the STM standard, but it is quite close. After user tests, the physical properties of the material are acceptable. It can be imagined that in order to successfully use MIM titanium as implants, new standards need to be established and accepted by the medical community. The MIM titanium market will also be limited to smaller implants, but its future market is huge. Another better material is nickel-free stainless steel, which can be used in the medical industry and other applications. This alloy has the unique advantage of MIM, which can mix element powders, form alloys during the sintering process after molding.

The application of IM in the medical market should be attributed to the birth of new forming technology. It combines the characteristics of plastic injection molding and sintering processes to produce small, complex, large-volume and near-full-density metal parts. The MIM industry will continue to develop a variety of alloys to meet more future needs.

Specific applications of MIM in medicine

1. Orthopedic implants

MIM technology can produce orthopedic implants with complex shapes, such as artificial joints. Compared with traditional processing methods, MIM technology has higher precision and lower waste, which can greatly reduce production costs. At the same time, MIM products have better biocompatibility and mechanical properties, and are more in line with the characteristics of human bones.

2. Surgical instruments

MIM technology can also be used to manufacture high-precision, complex-shaped surgical instruments, such as surgical forceps, suture needles, etc. Compared with traditional metal materials, MIM products have better wear resistance and corrosion resistance, which can greatly improve the service life of medical devices.

3. Stapler

Stapler is widely used in various surgical operations, generally divided into one-time or multiple use, and currently mainly imported and domestically produced. The traditional process is machining, which is very expensive. Dahong New Materials uses MIM technology to successfully develop stapler products, which can greatly reduce costs.

4. Surgical knife handle

After installing the surgical blade, it is used to cut or peel human tissue.

5. Knee implant parts

MIM technology has progressed slowly in the field of human implants, mainly because the certification and acceptance of products requires a long period of time. At present, MIM technology can be used to produce parts that partially replace bones and joints, and the metal materials used are mainly Ti alloys. Gelatin sustained-release microspheres coated porous titanium are non-cytotoxic and can be used as a good material for medical implants.

6. Surgical tools

Surgical tools require high strength, low blood contamination, and the ability to achieve aggressive disinfection procedures. The design flexibility of MIM technology can meet the application of most surgical tools. It also has process advantages and can manufacture various metal products at low cost. It is gradually replacing traditional production technology and becoming the main manufacturing method.

7. Orthodontic brackets

MIM technology was first used in medicine to make some dental orthopedic appliances. These precision products are very small in size, and have good biocompatibility and corrosion resistance. The main material used is 316L stainless steel. At present, orthodontic brackets are still the main products of the MIM industry. A two-way hook-type orthodontic bracket produced by MIM technology can increase the mechanical retention force by 30%. The friction of the bracket on the archwire can be greatly reduced by polishing after one-time forming by MIM. This product has been confirmed by Bjorn Ludwig to play a positive role in orthodontic surgery.

The demand for medical products is very large, and the structure of many products themselves is also very sophisticated and complex, requiring a new manufacturing technology to replace traditional production. Metal Injection Molding (MIM) is a new near-net-shape forming technology that can mass-produce products with complex shapes in a short period of time. It can meet the manufacturing requirements of medical products and has become an ideal manufacturing method.