Introduction: Metal injection molding, also known as MIM, is an advanced metal manufacturing process . It’s a cheap way to make metal parts that are really dense, have a lot of shapes, and work really well. MIM is a new way to make metal stuff that combines the flexibility of injection molding with the strength of powder metal sintering.

People like MIM because it makes metal parts that are strong, cheap, and have a lot of shapes. MIM is used in a lot of industries, like electronics, medical, industrial, and cars. This article will tell you how MIM works, what it’s good for, and what it’s not good for.

What is the Metal Injection Molding Process?

Metal injection molding (MIM) production process is a process for manufacturing high-precision, complex metal parts. It combines metal powder, injection molding, and sintering to produce MIM parts with tight tolerances and great surface finishes.

By using different sizes and shapes of metal powders, adding different additives, you can get MIM parts with different chemical and physical properties. The composition of the binder in each powder particle determines the final hardness of the part.

What is the Principle of Metal Injection Molding Process?

The injection molding process is divided into two stages: injection molding and sintering.

Injection molding

In the injection molding stage, the metal material is heated to a liquid state and then injected into the mold through a syringe. The temperature of the mold is low, so that the metal material cools and solidifies rapidly in the mold to form a metal billet with a certain shape and size.

sintering process

In the sintering stage, the metal billet is sent to a sintering furnace for high-temperature treatment. At high temperatures, the particles in the metal billet bond together better, making the metal billet denser and stronger. The sintered metal parts have good mechanical properties and heat resistance.

What are the Metal Injection Molding Advantages?

Compared to traditional metal production technology, metal injection molding (MIM) has a lot of advantages. After 30 years of continuous development of MIM technology, BRM can use this technology to produce MIM parts with large volume, multiple alloys, different sizes, and complex structures. Our summary of the advantages of MIM is as follows:

Structural Parts with Highly Complex Structures Can be Formed

The injection molding process technology uses an injection molding machine to inject product blanks to ensure that the material fully fills the mold cavity, which also ensures the realization of highly complex structures of parts. In the past, in traditional processing technology, individual components were first made and then combined into components.

When using MM technology, it can be integrated into a complete single part, which greatly reduces the steps and simplifies the processing procedures.

Compared with other metal processing methods, MIM has high dimensional accuracy of products, and no secondary processing is required or only a small amount of finishing is required. The injection molding process can directly form thin walls and complex structural parts. The shape of the product is close to the requirements of the final product.

The dimensional tolerance of the part is usually kept at around ±0.1 to ±0.3, which is particularly important for cutting down on the machining cost of cemented carbide, which is hard to machine, and reducing the processing loss of precious metals.

There is no restriction on shape design, which is suitable for almost all products. The tolerance that cannot be achieved by MIM molding can be achieved with the help of surface treatment.

The Microstructure of the Product is Uniform, the Density is High, and the Performance is Good

When you press, the mold wall and the powder and the powder and the powder rub against each other, and the pressure is uneven. This makes the microstructure of the pressed hair uneven. When you sinter, the pressed powder metallurgy parts shrink unevenly.

So you have to lower the sintering temperature to reduce this effect. But then you get big holes, low density, and poor material density, which makes the product weak.

Actually, injection molding is a fluid molding process. The presence of binders ensures that the powder is uniformly arranged, eliminating the uneven microstructure of the hair, and then the density of the sintered product can reach the theoretical density of its material.

Under normal circumstances, the density of the pressed product can only reach 85% of the theoretical density. The high density of the product can increase the strength, strengthen the toughness, improve the ductility, electrical conductivity and thermal conductivity, and improve the magnetic properties.

High Efficiency, Easy to Achieve Large-Scale and Large-Scale Production

The metal mold used in MIM technology has a lifespan similar to that of engineering plastic injection molding molds. Because metal molds are used, MIM is suitable for mass production of parts.

Since the blanks of products are formed by injection molding machines, the production efficiency is greatly improved, the production cost is reduced, and the consistency and consistent quality and repeatability of injection molded products are good, which provides a guarantee for large-scale and large-scale industrial production.

MIM is a process with greater flexibility, and you can make thousands to millions of parts a year very economically. Like castings and injection molded parts, MIM requires customers to invest in molds and tooling costs, so for small batches of parts, it usually affects the cost estimate.

Wide Range of Applicable Materials and Broad Application Fields

There are a lot of materials that can be used for injection molding. Basically, any powder material that can be cast at high temperature can be made into parts by MIM process, including difficult-to-process materials and high-melting-point materials in traditional manufacturing processes.

Also, MIM can do material formula research according to user requirements, make any combination of alloy materials, and make composite materials into parts. MIM can process many materials, including low alloy steel, stainless steel, tool steel, nickel-based alloy, tungsten alloy, cemented carbide, titanium alloy, magnetic material, KoVr alloy, fine ceramics, etc.

Although non-ferrous alloys of aluminum and copper are technically feasible, they are usually processed by other more economical methods, such as die casting or machining.

MIM Process Uses Micron-Grade Fine Powder

MIM uses fine powder with a particle diameter of 2-15μ, while traditional powder metallurgy uses powder with a particle size of 50-100μ. Small particle size can speed up sintering shrinkage, improve mechanical properties, extend fatigue life, and improve resistance to stress corrosion and magnetic properties.

Fine particle size not only increases the cost (about 1-10 times the price of traditional PM powder), but also easily agglomerates, increases the difficulty of uniform mixing, and the degreasing rate is relatively slow, thereby reducing the production efficiency of the MIM process.

Compared with traditional powder metallurgy, MIM adds about 30-55% (volume fraction) of organic binder to ensure that the powder binder system can be smoothly filled in the mold during injection.

So, to get a dense final product, you need to use fine powder that has a lot of sintering force. Another good thing about using fine powder is that the surface of the sintered part looks good. To make sure that MIM parts sinter well and have good properties, you want to use powder that’s as pure as possible and has as little oxygen as possible.

With complicated parts, you usually make them by breaking them down into individual parts and then putting them together. MIM is cheaper because you make the whole part at once and you don’t have to do as many steps.

Also, with traditional metal forming, the more complicated the part, the more it costs. With MIM, the cost is the same no matter how complicated the part is because you just make the mold more complicated. The more complicated the part, the cheaper MIM is and the more you save.

What are the Disadvantages Metal Injection Molding?

High Production Cost

Compared to powder metallurgy, the material cost of metal powder injection molding technology (MIM) is higher and the requirements for raw materials are more strict. This means that the diameter of the metal powder should be as small as possible. In order to achieve better performance, the metal powder injection molding (MIM) process requires the addition of a binder rather than powder metallurgy.

Therefore, the cost of using metal powder injection molding technology is more expensive.Compared with traditional plastic injection molding, it requires more post-processing steps, such as removing the binder and sintering, which can increase production time and cost.

Difficulty in Powder Quality Control

Metal powder injection molding technology must ensure multiple parameters, such as powder size, distribution, and shape, to guarantee the accuracy and strength of the finished product. However, since the production and processing of powders are easily affected by multiple factors, such as the environment and equipment, the quality control of powders is difficult .

Unsatisfactory Surface Quality

Metal powder injection molding technology has quality issues related to organization and surface. Metal powders often have problems like uneven density, pores, and defects during the injection molding process. These problems not only affect the working performance of the finished product, but also lead to unsatisfactory surface quality, easy rust and damage.

High Requirements for Equipment And Materials

Metal powder injection molding (MIM) technology needs special injection machines and sintering equipment, which are expensive and hard to maintain. Meanwhile, the production, storage, and processing of metal powders also need strict environments and conditions, which is not good for enterprise production and management.

MIM Parts are Usually Small in Scale

Because the metal powder injection molding technology furnace has a small operating space, the MIM parts produced are usually small.

This technology is suitable for the manufacturing range of metal powder injection molding technology limited to 10-15mm, such as precision odd-shaped parts, complex parts, powder metallurgy micro gears, and small modulus gears. This is also one of the reasons why the development of MIM technology is greatly restricted.

Production Factors

Powder metallurgy manufacturer Xintaixing believes that because molds are expensive, metal powder injection molding technology is better for large-scale production. So, for some small metal parts with complex shapes but not high requirements, CNC machining may be cheaper and more affordable.

What are the Fields of Application of Metal Injection Molding Technology?

Automotive industry: Metal injection molding technology is used a lot in the car industry to make engine parts, gears, camshafts, and stuff.

Electronic industry:In the electronics industry, we use metal injection molding technology to make metal casings and parts for products like mobile phones, computers, and TVs.

Medical devices:Metal injection molding technology is also widely used in the medical metal injection molding, such as manufacturing surgical instruments , dental implants, etc.

Other industries:Metal injection molding (MIM) technology is also used in aerospace, energy, chemical, and other industries.

Conclusion

In short, metal powder injection molding (MIM) is a fancy way to make metal parts. It’s used in a lot of different industries because it can effectively produce high-density, complex geometries metal parts . It’s like regular plastic injection molding, but for metal.

You can make parts that are really strong and have a lot of detail. But MIM is not perfect. It’s expensive, it’s hard to control the quality of the powder, and you need special machines to do it. These things make it hard to use MIM for big production runs or for parts that need to be cheap.

So, MIM is good for some things, but not for everything. If you want to make parts, you need to think about what you want to make and how much it costs.