As customers are more and more inclined to product miniaturization, the demand for small durable parts in the industry is increasing. As a result, more manufacturers require large quantities of complex small metal parts. Metal injection molding (MIM) process can meet this demand and save a lot of costs for automotive, industrial, medical and electronic industries. Here, we are going to explain everything you need to know about metal injection molding, the working process, advantages, applications and more.
What Is Metal Injection Molding
Metal injection molding (MIM) is a new kind of powder metallurgy near net forming technology, which is derived from the plastic injection molding industry. As we all know, MIM can produce various complex shaped products with a low price, but the strength of plastic products is not high, Metal or ceramic powder can be added into plastics to obtain products with high strength and good wear resistance. In recent years, the idea has evolved to maximize the content of solid particles and completely remove the binder and density the preform during the subsequent sintering process. This new powder metallurgy forming method is called metal injection molding.
How Does Metal Injection Mold Work
The basic process is as follows: firstly, the solid powder is mixed with the organic binder evenly, then granulated and injected into the mold cavity for curing in the state of heating and plasticizing (～ 150 ℃). Then, the binder in the blank is removed by chemical or thermal decomposition, and finally the final product is obtained by sintering and densification. MIM process consists of four main steps, which use key processes to produce metal injection molded parts with excellent quality and dimensional repeatability:
Mixing of raw materials
It is important to ensure the uniformity of the raw material because it is made up of very fine metal powders (less than 22 microns). These powders are carefully and thermally mixed with the polymer binder to form a uniform mixture, which is then cooled and granulated to form the raw material. The material is then fed into the molding machine.
Molding
Many advantages of MIM function are realized in the forming process, in which complex contour, hole, small radius, logo and text can be molded into parts. In this step, the raw material is heated and injected into the molding equipment and the part is created. This molding process generates almost no waste and uses a wide range of automation technologies to eliminate unnecessary part handling and provide a consistent and cost-effective manufacturing solution.
Catalytic degumming
Phillips medisize’s advanced knot removal technology is the most effective form of knot removal. Using polymer chemistry, introducing catalysts, 90 percent of the binder is removed from green parts, which produce parts with excellent shape and dimensional integrity. When the binder is removed, the result is called the “Brown” section. The brown part is composed of porous matrix of metal powder and enough adhesive to keep its shape.
Sintering
In the final step, brown parts are sintered using the temperature and atmosphere curves selected for the alloy being processed. At the lower temperature of the sintering cycle, the residual polymer binder is removed. With the increase of sintering temperature, the particles are allowed to fuse and bond with each other, so that the structure is combined and the porosity is reduced.
Why Choose Metal Injection Molding
MIM is a process of mixing granular metal powder with binder material to form a shape and solidified raw material. This method creates complex precision shaped parts at a price of 50% lower than the cost of machining or investment casting. Parts that are very suitable for MIM are those that require a lot of processing setup or assembly operations, if they are manufactured by any other metal forming process. The main advantage of MIM is the ability to produce complex metal geometries without machining. By designing components for MIM process, the number of parts and assembly time are reduced, and the total cost is saved.
Advantages Of Metal Injection Molding
1.Excellent surface finish
2.Excellent corrosion resistance
3.High strength and high-end products
4.Complex metal geometry
Disadvantages Of Metal Injection Molding
1. Machining is necessary to remove the excess copper after infiltration, which raises machining costs afterwards
2. The process costs are high
3. The process is complicated,
4. The output decreased, and the application of complex shaped components is unfavorable.
Application Of Metal Injection Molding
1.Computer and its auxiliary facilities: such as printer parts, magnetic core, striker pin, drive parts;
2. Tools: such as drill, cutter head, nozzle, gun drill, spiral milling cutter, punch, socket, wrench, electrical tools, hand tools, etc;
3. Household appliances: such as watch case, watch chain, electric toothbrush, scissors, fan, golf head, jewelry chain link, ball pen clamp, cutting tool head, etc;
4. Medical machinery parts: such as orthodontic frame, scissors, forceps;
5. Military parts: missile tail, gun parts, warhead, liner, credit parts;
6. Electrical parts: electronic packaging, micro motor, electronic parts, sensor parts;
7. Mechanical parts: such as loosing machine, textile machine, crimping machine, office machinery, etc;
8. Automobile and marine parts: such as clutch inner ring, fork sleeve, distributor sleeve, valve guide, synchronous hub, airbag parts, etc.
History And Current Situation Of Metal Injection Molding
Parmatech company, California, USA, invented this technology in 1973. In the early 1980s, many European countries and Japan also invested great efforts in the research of this technology, and it has been rapidly promoted. Especially in the mid-1980s, this technology has achieved rapid development since its industrialization, increasing at an alarming rate every year. So far, more than 100 companies in more than 10 countries and regions such as the United States, Western Europe and Japan are engaged in the product development, research and sales of this technology. Japan is very active in competition and performs well. Many large companies are involved in the promotion of MIM industry, including Pacific metal, Mitsubishi steel, Kawasaki iron, Kobe Steel, Sumitomo mine, Seiko Epson, Datong special steel, etc. At present, there are more than 40 companies specialized in MIM industry in Japan, and the total sales value of MIM industrial products has already surpassed that of Europe and directly caught up with that of the United States. So far, more than 100 companies around the world have been engaged in the product development, research and sales of this technology. As a result, MIM technology has become the most active frontier technology field in the new manufacturing industry, which is regarded as the pioneering technology in the world metallurgical industry and represents the main direction of powder metallurgy technology development.