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What Is Metal Injection Molding?

Metal injection molding (MIM) is a metalworking process in which finely-powdered metal is mixed with binder material to create a feedstock. The feedstock is then solidified and shaped to produce the final product.

Metal injection molding is ideal for simplifying the production of high-volume products or products that have complex shapes.

Why Is Metal Injection Molding So Popular?

The MIM process is one of the more popular metal fabrication processes today. Consider this fact: from 1986 to 2004, the MIM market grew from USD 9 million to roughly USD 380 million – quite a substantial jump. One of the reasons the process is so popular is its efficiency and its cost-effectiveness.

When the products are molded, only quantities of 100 grams or less per “shot” are put into the mold, but each shot can be put into multiple cavities. This means that lots of small items can be made simultaneously, which cuts down on each item’s production cost.

The feedstock used in the process can consist of any number of metals, but the most common types are stainless steel. When the products are molded, the binder material is then removed, and the metal particles go through a refinement process to maximize the strength and durability of the material. This process often shrinks the size of the item by roughly 15%.

Is The Metal Injection Molding Process Complicated?

The MIM process has evolved considerably since 1956 when it was first popularized. The process saw its most significant advances during the 1990s, resulting in products being far more durable and more functional than similar methods up to that point. Today, the process typically follows these steps:

  • Metal powders are combined with polymers such as wax and polypropylene binders to produce a “feedstock” mix.
  • The feedstock is injected as a liquid into injection molding machines to mold them into the proper shape.
  • The molded part, also called the “green part”, is cooled first then removed from the mold.
  • Next, binder removal takes place using any one of a variety of materials, including a catalytic process, thermal furnaces, and so on. Only part of the binder is removed.
  • The debinding and sintering processes are up next. The latter is a method whereby material is compacted and formed using either pressure or heat, but it always stops before the material turns completely into a liquid.
  • Liquid phase sintering is sometimes used, in which partial melting occurs when the MIM parts are being sintered.
  • Because diffusion rates are high, shrinkage is always a part of the process.

This general MIM procedure or one very similar to it is used every day by thousands of metal fabricators around the world.

The Many Advantages of Metal Injection Molding

There are several advantages to the metal injection molding process, especially when comparing it to other methods such as CNC machining. This process makes it much easier to produce complex metal parts that are sometimes impossible to create using other metal fabrication processes. The MIM properties are roughly equivalent to wrought alloys, and you can manufacture net shapes with minimal waste.

When it comes to fabricating high-volume parts and small, complex parts, MIM is more cost-efficient and a lot less time-consuming than most other metal fabrication methods. Both production time and finishing time are relatively short, which are just some of the reasons why the process is such a popular one today.

Some popular products that are made using metal injection molding include:

  • Computer hinges for laptops
  • Watch cases
  • Plugs for cell phones
  • Products for industries such as medical/dental, aerospace, firearms, automotive, commercial, industrial, and more

Indeed, if you can think of a specific industry, it is almost a certainty that they are operating using items that are made using injection molding machines and the MIM process.

Applications for MIM Processes

There are several applications where injection molding comes in handy. For example, one common consideration with metal fabrication is the wall thickness of the item you need to be produced.

If the wall is very thin – for example, 100 micrometers – your item is a good candidate for metal injection molding.

Metal injection molding is also a process to consider if you’re interested in a more eco-friendly way of mass-producing products. Although some of the older injection molding machinery generates toxic emissions such as formaldehyde, the newer machines are much cleaner and produce far less waste than CNC machining, and other processes do. In fact, with a little work and a few revisions, MIM processes might be even cleaner in the future.

Starting A Metal Injection Molding Project

Metal injection molding is great for producing very intricate parts quickly and efficiently. The metal injection molding process is efficient, easily repeatable, and cost-effective. In a single step, intricate parts can be mass-produced in high volume and shaped to perfection. Best of all, after your first production run, setting up future runs is fast and easy.

If you’re looking for an experienced metal injection molding partner, we’d be happy to give you a quote on your project. The Federal Group USA has been a leading contract manufacturer for more than forty years. Give us a call or send us an email today to get a quote for your metal injection molding project.