Metal powder injection moulding - revolution in metal component production

Metal injection moulding (METAL INJECTION MOLDING - MIM) is a pioneering technology for the cost-effective production of high-quality metal components. We report on the history of MIM, the manufacturing process, advantages and typical applications. Let's dive in!

Contents

History of metal powder injection moulding
What is metal powder injection moulding?
Advantages of metal powder injection moulding
MIM applications
Machines used in metal injection moulding
Conclusion

History of metal injection moulding (MIM)

The beginnings of powder injection moulding date back to the 1970s. At the time, researchers were looking for innovative methods to produce complex metal components cost-effectively. The idea of combining powder metallurgy with injection moulding processes emerged in response to the challenge of producing high-precision parts with complex shapes that were not possible using conventional methods.

Over time, the techniques and understanding of metal powder injection moulding have been continuously improved. New materials, binders and sintering techniques were developed to optimise the mechanical properties and quality of the end products. This has also been applied to technical ceramics. Today, metal powder injection moulding is known as Metal Injection Moulding (MIM) and has become a key manufacturing method for high-quality metal components.

What is Metal Injection Moulding (MIM)?

MIM is an innovative manufacturing process that combines the advantages of powder metallurgy and plastic injection moulding. It enables the cost-effective production of high-precision and complex metal components in large quantities. The MIM process consists of six steps:

• Powder preparation phase:  In this phase, fine metal powders are carefully selected and mixed with binders and additives. The resulting powder mixture forms the basis for the subsequent steps.
• Injection moulding of the compound: The prepared powder is fed into an injection moulding machine, where it is processed into a mouldable compound using the binder. This mass can be injected into complex moulds. It is called a green compact or green part. 
• Density determination: The density of the green part is usually measured after injection moulding, i.e. immediately after the part has been moulded. The measurement is typically carried out using non-destructive testing methods such as the Archimedes method. 
• Debinding: After injection moulding, the workpiece is heated in an oven to remove the binder. This makes the workpiece porous, but it retains its shape.
• Sintering: The workpiece is sintered in a controlled furnace at high temperatures, causing the metal particles to fuse together. The workpiece becomes dense and acquires its final mechanical properties.
• Post-processing: Some parts may require post-processing after sintering in order to optimise tolerances and surface quality.

Advantages of powder injection moulding 

MIM offers a number of advantages that make it an attractive choice for metal component production:

• Complex geometries: Metal powder injection moulding can be used to produce highly complex geometries that would be difficult to realise with conventional production methods. This enables the construction of precise and functional parts with a high degree of design freedom.
• Material efficiency: MIM utilises the material more efficiently than traditional machining techniques, as only as much material is used as is actually required for the end product. This significantly reduces material waste and saves costs.
• Cost savings: As MIM produces complex parts in a single process step, fewer assembly steps are required, resulting in significant cost savings. The mass production of MIM components is more cost-effective than the production of individual parts.

Applications of metal injection moulding

MIM is widely used in various industries, including:

• Medical technology: Metal powder injection moulding is used for the production of surgical instruments, implants and other medical devices that require high precision and biocompatible properties.
• Automotive industry: In the automotive industry, MIM components are used in gearboxes, brakes and electric drive trains to improve vehicle performance and efficiency.
• Electronics: It enables the cost-effective production of electronic components such as connectors, switches and sensors.
• Defence and aerospace: In these industries, this process is used for the production of parts that require high strength and heat resistance.

Machines for metal injection moulding (MIM)

Metal injection moulding is a high-precision manufacturing process that places special demands on the machines used. These machines must offer high performance and precision in order to mix the fine metal powders and special binders homogeneously and inject the mass precisely into the moulds. Controlled temperature conditions in the ovens are crucial for debinding and sintering in order to achieve the desired mechanical properties. The selection of modern and efficient powder injection moulding machines is crucial to the success of the manufacturing process.

The most important machines are:

Powder mixer: A powder mixer is used to mix the fine metal powders with special binding agents and additives to form a homogeneous mass. The even distribution of the components is crucial for the quality of the end products.

Injection moulding machine: The injection moulding machine is central to the process. It injects the prepared compound into the moulds that define the desired geometry of the parts. State-of-the-art machines and precise process control are crucial to ensure the quality and consistency of the MIM parts.

Debinding oven: After metal injection moulding, the moulded parts are heated in a debinding oven to remove the binder. This debinding process is crucial in order to create uniform porosity in the workpieces..

Sintering furnace: The sintering furnace is a high-temperature furnace that sinter the debinded parts, causing the metal particles to fuse together. This step gives the parts their final strength and density.

Post-processing machines: Depending on the requirements and the desired end product, further post-processing steps may be necessary. These include, for example, grinding, polishing or surface treatment.

The selection and use of specific machines depends on the requirements of the respective MIM process and the desired properties of the manufactured parts.  

Conclusion

Metal powder injection moulding is undoubtedly a revolutionary technology for the production of high-quality metal components. The advantages of this process in terms of complex geometries, material efficiency and cost savings make it a popular choice in various industries.