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Die Casting vs Metal Injection Molding: A Detailed Comparison

Customers seeking parts manufacturing have a wide variety of choices on how the part is made. From small intricate parts to large simple components, the method you choose may come down to a variety of factors such as raw materials, product design, and costs. Die casting and metal injection molding are two methods that can suit many customers in various industries, though it’s important to understand the pros and cons of each process before selecting one for your project.

Metal Injection Molding

The metal injection molding (MIM) manufacturing process uses injection molding equipment to create small and intricate parts in a single step. These manufactured parts possess relatively high strength and durability. In addition, the molded parts also have good wear characteristics. Manufacturers may recommend this process when customer geometry requires thin walls because this is a typical design for metal injection molding request.

Many customers select metal injection molding due to the cost considerations. The process is low in cost to perform and provides batch parts with good repeatable quality. Manufacturers also experience less waste when producing parts using this process, which leads to lower costs that are passed to the customer. Another advantage to this process is that finished parts typically don't need machining or finishing once they’re completed.

Metal Injection Molding Process

Metal injection molding material is typically called a feedstock. Feedstocks are compounded by combining powder metal material and a polymer binder. This binder is used as a carrying agent to transfer the powder metal into the custom designed mold. 

The motion is controlled by heat, which melts the binder and is pushed by a hot screw into the mold. Once this is complete, the molded part cools and is removed from the mold by an ejection process. 

The next step is to remove that binder material that was only utilized to carry the powder metal into the mold. The removal process consists of either a thermal, solvent, or water catalyst depending on the binder system selected. 

The debound part then goes through a sintering process. This is typically done in a batch furnace, but can also be done in a continuous belt furnace. The objective of sintering is to consolidate and mechanically bond the individual particles of powder metal. This is where the part reaches its typical mechanical and chemical properties based on the alloy system utilized.

Common MIM Applications

Metal injection molding excels as a manufacturing process due to allowing manufacturers to create complex, intricate, and small parts with tight tolerances and thin walls. Some MIM applications include:

  • Firearms industry: triggers, sights, bolts, ejector, barrel release
  • Medical industry: joint replacement parts, surgical instruments, drug delivery systems
  • Automotive industry: electrical connectors, system controllers, shift levers
  • Industrial industry: drone parts, micro gears, machinery components
  • Aerospace industry: engine components, flap screws, valve holders
  • Electronics industry: mobile phone componentry, smart wear, cable accessories

Die Casting

Die casting manufacturing processes involve taking non-ferrous molten metals and forming them into parts using dies. There are numerous die parts that may be used that can form various different shapes and internal components. These dies consist of single-cavity dies that make a single part, combination dies that make several different parts at once for a single assembly, unit dies that use one cast cycle to make several different parts, and multiple-cavity dies that provide several parts that are identical.

Customers may select this process because it is simple. Die casting can mass produce highly durable and complex parts, while still retaining original specifications, allowing for the exact duplication of parts.

Die Casting Process

During the die casting process, a clean die is clamped shut and lubricated to control internal temperatures as molten metal is injected into the die using high pressures. The part is allowed to cool as it is then ejected from the die.

There are typically three die casting processes: gravity die casting, cold die casting, and hot die casting. 

  • Gravity die casting uses gravity to move the molten metal into the mold. 
  • Cold die casting requires workers to ladle the molten metal into the machine that injects the molten metal at high pressures. 
  • Hot die casting has a furnace that feeds the molten metal directly into the injection machine using a gooseneck.

Common Die Casting Applications

Die casting is extremely versatile, allowing it to be used for customers in a vast variety of industries. A few of these industries include the following:

  • Firearms industry: triggers, trigger guards, safeties
  • Medical industry: surgical devices, peristaltic pumps, blood analysis machines
  • Automotive industry: gear housings, powertrain systems, engine components
  • Industrial industry: outboard gear case, hydrostatic axles, steel liner inserts
  • Electronics industry: electrical housings, antenna mounts, RF filters

Die Casting vs MIM

When comparing die casting processes to metal injection molding, there are several key differences that may impact which method to use for your project. Let's check out some aspects to consider:

  • Precision & Tolerances: Metal injection molding creates very precise parts with relatively tight tolerancing. On the other hand, die casting can have varying dimensions which usually require the part to be trimmed to meet specifications. Also, die casting does not allow much control over wall thickness.
  • Materials Used: MIM allows for both non-ferrous and ferrous materials. Die casting typically uses non-ferrous metals.
  • Surface Finishing: Die casting may require excess metal to be trimmed off and offers a medium surface finish. MIM allows for a high surface finish that typically doesn't require additional finishing.
  • Tooling/Manufacturing Costs: Costs are dependent on the complexity of the part. While metal injection molding offers low costs, it does have higher process costs than die casting. Die casting may be cheaper than MIM, depending on the specific application.
  • Mold Differences: MIM allows for greater flexibility when it comes to the mold, yet the mold has a lower lifespan. Die casting has good flexibility, yet not as much as MIM methods. Dies used in die casting, however, typically last longer.

Which Method Will You Choose?

Both MIM and die casting have a wide variety of benefits, so at times it may be a tough choice. Ultimately, when choosing a manufacturing method, you have to take your design, desired materials, and the end use of the part you’ll be manufacturing into consideration.

If you’d like to learn more about MIM and other types of metal manufacturing, check out our resource page.