Developed in the 1970s, the metal injection moulding process involves mixing finely powdered metal with the binder material. It is done to create a feedstock that can be later shaped and solidified using injection moulding.
Metal moldings help create complex components using thermoplastic additives. After the moulding process is completed, the product goes through a conditioning process, in which the binder and powders are removed. The products are then used in various industries.
The metal moulding industry was worth $1.5 billion in 2015 and is growing rapidly.
That said, let’s look at how the metal moulding process works.
1 – Preparing the Feedstock
As mentioned above, the primary raw materials in the metal molding process are metal powders and binders (usually thermoplastic). Remember, the binder is removed from the product after being given the shape and solidified.
When it comes to powders, they determine the properties and application of the final product.
To prepare the feedstock, you need to mix the blended metal powder with the thermoplastic binder at a high temperature. You will need a shear roll extruder or a kneader to do it. The mixture will then be required to be granulated with granule sizes of several millimetres.
However, the good thing about feedstock is that it can be purchased (if you cannot prepare them). You can easily find many suppliers offering feedstock.
2 – Injection Molding
The next step is injection molding. In this, the green part (molded one) is cooled, and when it comes to room temperature, it is removed from the product. Then, a small portion of the binder material is removed to create parts with an interconnected pore network without affecting the product’s actual shape.
Even after the binder removal, there will be some binder present in the product. This is because they are responsible for holding the metal powder together. However, the pores speed the process of evaporation of the residual binder.
3 – Sintering
This is where most of the pore volume occupied by the binder is eliminated. As a result, the MIM parts experience a subsequent shrinkage. It could be as high as 15% to 20%. However, you can further process the sintered MIM parts using conventional metalworking processes like heat and surface treatments, depending on your requirements. You can then leverage HIP (Hot Isostatic Pressing) to remove any residue properties completely.
When the heating is done in the vacuum, you can reach 96-99% solid density. Once the sintering process is completed, the MIM component will be compatible with the metal conditioning treatments, including precipitation hardening, carburizing, annealing, passivating, and plating.
Applications
Metal molding process is used in various industries. It includes commercial, medical, dental, firearms, aerospace, and automotive industries. It is usually used in areas where it is difficult to manufacture a product through other means of fabrication.
The best part about the metal molding process used in these industries is that it can include product codes, part numbers, or date stamps. These details can make the application use easier while ensuring the industry that it complies with all their requirements.
The reason the metal injection moulding process is successful is that it has the ability to combine several operations into one. As a result, manufacturers save both time and money.
Conclusion
The metal molding process helps give shape to different products that are used in various industries. When it comes to feedstock, you can either create it or purchase it from suppliers. You can then leverage injection moulding, binder removal, and then sinter the product to get the final output.
