Metal injection molding (MIM) is a new manufacturing technology combining powder metallurgy and plastic forming process. Firstly, the selected powder is mixed with the binder, then the mixture is granulated, and then injected into the required shape. Polymerization imparts the characteristics of its viscous flow to the mixture, which contributes to the uniformity of forming, cavity filling and powder filling. After forming, the binder is removed, and then the degreased billet is sintered.
The sintered products not only have the same complex shape and high precision as the products produced by plastic injection molding but also have the same physical, chemical, and mechanical properties as the forgings. In traditional machining technology, for complex parts, is usually to decompose and make a single part, and then assemble; After using PIM technology, it can be considered to integrate it into a complete single part, which greatly reduces the production steps, simplifies the processing procedures, saves costs and improves efficiency.
MIM technology not only has the advantage featured by less process as conventional powder metallurgy, such as low density, uneven material, low mechanical properties, difficult to form thin wall and complex structure. The MIM technology is especially suitable for mass production of small, complex, and special metal parts.
1. High design freedom
Compared with other metal forming methods, MIM can manufacture more complex parts. Basically, all structures that can be realized by injection mold can be applied to MIM.
2. More material options
MIM can use almost most metal materials. Considering the cost, the main application materials include iron-based, nickel-based, copper-based, titanium-based metals or alloys.
3. Excellent physical and chemical properties
Since the sintering density of MIM is very close to the theoretical density, its physical and chemical properties are also very excellent, such as mechanical strength, which greatly surpasses the traditional powder metallurgy.
4. Exquisite appearance
The surface roughness (RA) of the MIM sintered billet can reach 1 μm. The dazzling appearance effect can be obtained through various surface treatment methods.
5. Higher-dimensional accuracy
MIM can generally achieve tolerance accuracy of ±0.5%. With other processing methods, higher dimensional accuracy can be obtained.
6. Strong and flexible mass production capacity
MIM can flexibly adjust and rapidly increase the output and can respond quickly from hundreds of pieces per day to hundreds of thousands per day.
7. Processing concept of environmental protection
The utilization rate of raw materials is close to 100%. It is a near-net forming technology, which can effectively avoid material waste.
Metal injection molding can be traced back to the powder injection molding preparation of ceramic spark plugs in the 1920s. In the following decades, powder injection molding mainly focused on ceramic injection molding.
It was not until 1979 that the metal injection molding products of pharma tech company established by wiech and others won two awards, and wiech and rivers successively won patents at that time that powder injection molding began to turn to metal injection molding.
In the past, due to the lack of suitable powder and raw materials, too high price, imperfect knowledge platform, immature technology, short time for people to understand and accept the market, too long production cycle (including mold manufacturing), insufficient investment and other reasons, its development and application were relatively slow.
In order to solve the difficulties of MIM technology and promote the practicability of MIM technology, the United States formulated an advanced powder industry plan in the mid-1980s, which includes 18 topics related to injection molding. Subsequently, Japan and Germany also actively carried out MIM development and research.
With the deepening of MIM research, the development of new binders, the continuous progress of pulverizing technology and the degreasing process, it has been industrialized in the early 1990s. After more than 20 years of effort, MIM has become a rapidly developing and most promising new near net shape forming technology in the field of international powder metallurgy and is known as one of the most popular metal parts forming technologies in the world.