Plastic injection molding offers incredible design flexibility.
Fabricating with metal results in parts and components that are extremely durable.
When you combine the two, you end up with a process unlike any other – the metal injection molding (MIM) process.
Leveraging the advantages of plastic injection molding and metallurgy, MIM is an ideal manufacturing solution for a wide variety of applications.
In This Article…We’ll explore the metal injection molding process from start to finish, looking at:
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MIM is a variation of plastic injection molding, that is ideal for high-volume, small metal components with thin walls and fine details. Metal injection molding has very few restrictions on design, with the capability to produce extremely complex parts.
While MIM can create highly repeatable parts, the process itself is fairly simple.
While there are many design factors to take into consideration, the MIM process can be broken down into four steps:
In the metal injection molding process, materials and alloys are broken down into metal powder and then mixed with a binder to create the feedstock.
Typically, the binder is a thermoplastic polymer allowing the feedstock to take shape, and the powder varies depending on the desired properties of the final molded product. Once you have the blended mixture, the feedstock is ready to be injected.
The feedstock is injected into the mold cavity under high pressure to form the final component. The cavity should be designed with 20% extra capacity to account for part shrinkage during sintering (more on this later).
Once the feedstock is injected, it’s left to cool and solidify and then removed from the mold. This newly created piece is known as the “green” part.
In the first step, the binder was mixed with metal powder to create the feedstock. Now after the feedstock has been injected into the mold cavity, the binder needs to be removed from the metal. The debinding can happen in two ways:
Thermal debinding is typically inexpensive, but has a lengthy processing time – solvent debinding, is more consistent and quick, with the only downside being it’s not as eco-friendly as other methods. Whether through solvent or thermal debinding, the part is now prepared for the final step – sintering. At this point, the part is now referred to as a “brown” component.
The part can shrink by upwards of 20% or more, densifying the remaining part, and achieving a part density of 95-98%, and the final strength and structure are formed.
While MIM has many advantages to the process, there are several capabilities that are commonly overlooked:
While thin walls are common in plastic injection molded parts, it's not a common feature in metal parts. However with MIM, parts can be produced with thin walls and complex shapes.
In addition to high durability, MIM also produces quality, precise parts. The MIM process is highly repeatable, so each part comes out exactly the same. This is crucial when producing in high volumes so each part meets the desired requirements.
Why choose MIM over competing methods that can produce precise parts?
Efficiency.
Without sacrificing quality, MIM remains relatively inexpensive and efficient looking at the long-term benefits. Up front, MIM may require an investment due to the cost of the molding machine, mold tool, and other parts needed. However, MIM produces in high volume, so your return on investment happens in a very short time.
With all the advantages metal injection molding has to offer, it’s commonly used in many applications from the medical industry to the agricultural field, to even in your daily consumer items.
MIM is frequently used in the medical industry to produce precise medical devices such as:
As mentioned above, metal injection molding takes on the design flexibility of plastic, but the durability of metal, which is highly sought after in the medical industry – as well as the agricultural field. MIM is used in many agricultural applications from tractor parts to pruning shears.
Aside from uses in agriculture, objects produced by metal injection molding are probably used in your daily routine. Since MIM specializes in producing high-volume, small complex parts, cell phones, and electronic devices typically contain these components.
Metal injection molding can be used across a wide range of materials to create your perfect component.
Even though investing in MIM can be a complex, in-depth process – getting started with the investment will be worth the return in the end.
When considering metal injection molding for your production, it’s best to consult with an expert to ensure it’s the best fit. Book time with one of ours today: