Metal Injection Molding vs Die Casting
Metal Injection Molding Definition
Metal Injection Molding (MIM) was invented in the 1970s by Raymond Welch. It’s a process used to create metal parts and works similarly to plastic injection molding. However, in MIM, metal powder coated with a thermoplastic binder is used instead of plastic. This binder is later removed, unlike in plastic molding, where materials like glass or ceramic fibers are permanently added to improve the part’s strength.
Here's How MIM works
Preparation: A mixture of metal powder and binder is prepared and fed into an injection molding machine.
Injection: The machine has a heated barrel with a screw that pushes the mix through, heating and melting the binder. The screw compresses the mixture, heating it further, and then injects it into a mold.
Molding: The mixture fills the mold, forming a “green part” once it cools and solidifies. This green part still contains the binder.
Debinding: The green part is treated with solvents or heat to remove most of the binder, creating a “brown part.”
Sintering: The brown part is then heated in a furnace. This step removes any remaining binder and causes the metal particles to fuse together, shrinking the part by 15-30%, depending on the material used. This process gives the part its final density and mechanical properties.
Metal injection molding is great for making small, detailed parts with tight tolerances and thin walls. It is commonly used in:
Firearms: Parts like fire control group components, sights, bolts, and ejectors.
Medical: Items such as joint replacement parts, surgical instruments, and drug delivery systems.
Automotive: Components like electrical connectors, system controllers, and shift levers.
Industrial: Parts for drones, micro gears, and machinery components.
Aerospace: Engine components, flap screws, and valve holders.
Electronics: Mobile phone parts, smart wear, and cable accessories.
Die casting Definition
Die casting is a way to make metal parts by injecting molten metal into a mold. This method was invented in 1838 and patented in 1849. Originally, lead and tin were used, but by 1914, aluminum and zinc were also used. Today, metals like magnesium, copper, and silicon are common in die casting. This process is mainly for non-ferrous metals, though ferrous metals can be used but are rare.
The molten metal can be injected into the mold under high pressure or allowed to flow in by gravity. After the part cools, it is removed from the mold. This cooling process can take up to a minute, depending on the size and thickness of the part. Any extra material, such as gates, runners, and flash, needs to be removed, either manually or with a press die.
Here's How Die Casting Process works
In die casting, a clean die is clamped shut and lubricated to manage internal temperatures. Molten metal is then injected into the die under high pressure. After the part cools, it is ejected from the die.
There are three main die casting methods: 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: Workers ladle the molten metal into a machine that injects it under high pressure.
Hot Die Casting: A furnace directly feeds the molten metal into the injection machine using a gooseneck.
Die Casting Applications
Die casting is very versatile and is used in many industries, including:
Firearms: Parts like triggers, trigger guards, and safeties.
Medical: Items such as surgical devices, peristaltic pumps, and blood analysis machines.
Automotive: Components like gear housings, powertrain systems, and engine parts.
Industrial: Parts like outboard gear cases, hydrostatic axles, and steel liner inserts.
Electronics: Items such as electrical housings, antenna mounts, and RF filters.
Metal Injection Molding vs. Die Casting
When choosing between metal injection molding and die casting, consider these five key differences:
Precision & Tolerances: The level of accuracy and detail each process can achieve.
Materials Used: The types of metals suitable for each method.
Surface Finish: The smoothness and quality of the final surface.
Tooling/Manufacturing Costs: The expenses involved in creating and using the molds.
Mold Differences: The design and construction of the molds used in each process.
Precision & Tolerances
Metal Injection Molding: MIM creates very precise parts with tight tolerances.
Die Casting: Die casting can result in varying dimensions, often requiring trimming to meet specifications. It also offers less control over wall thickness.
Materials Used
Metal Injection Molding: MIM can be used with both non-ferrous and ferrous materials.
Die Casting: Die casting typically uses non-ferrous metals, which do not contain iron, unlike ferrous metals.
Surface Finish
Die Casting: Die casting often requires trimming excess metal and provides a medium-quality surface finish.
Metal Injection Molding: MIM offers a high-quality surface finish that usually doesn’t need additional finishing.
Tooling/Manufacturing Costs
Costs depend on the part’s complexity.
Metal Injection Molding: MIM has lower tooling costs but higher process costs than die casting.
Die Casting: Die casting can be cheaper than MIM, depending on the application.
Mold Differences
Metal Injection Molding: MIM molds offer more flexibility but might not last as long.
Die Casting: Die casting molds have good flexibility, though not as much as MIM molds, and typically have a longer lifespan.
Meta Build Industries specializes in manufacturing high-precision metal injection molding (MIM) parts. Our advanced MIM technology allows us to produce complex, intricate components for various industries, including automotive, aerospace, medical, and electronics. Committed to quality and innovation, Meta Build Industries delivers reliable, cost-effective solutions tailored to meet the specific needs of our clients.