In precision manufacturing, process selection is a critical step. This is because a suitable and excellent metal forming process can directly determine the performance, quality, and cost-effectiveness of the parts. Metal injection molding and die casting, as the two most widely used processes, each have their pros and cons and are suitable for different application scenarios. Now, if you are unsure which process is more suitable for your project, feel free to read this article. I believe that after reading this article, you will find the answer.
What is Metal Injection Molding(MIM)?
Metal injection molding (MIM) is a precision manufacturing process that combines powder metallurgy with plastic injection molding. Ultra-fine metal powder is mixed with an organic binder to form a feedstock, which is then pressed into a mold using an injection molding machine. After undergoing the two post-processing steps of degreasing and high-temperature sintering, the feedstock is finally made into a dense metal part.
The most prominent advantage of MIM is that this process can form small, precise parts with extremely complex geometries in one go. Additionally, this process supports the machining of high-performance materials such as stainless steel, titanium alloys, and tool steel.
What is Die Casting?
Die casting is a metal forming process. In this process, molten metal is injected into precision metal molds under high pressure. After cooling and solidifying, the part is removed from the mold, resulting in a metal component with precise dimensions. Die casting is fast and highly repeatable, making it ideal for high-volume production.
What Is the Difference Between Metal Injection Molding and Die Casting?
Alright, next comes the specific comparison section. I will explain the differences between these two processes to you from various aspects.
Size & Weight
This is one of the most notable differences between the two processes. Die casting is more suitable for manufacturing medium and large-sized parts, while metal injection molding is more suitable for producing small precision parts.
MIM: Part weights are typically limited to between 0.1 g and 100 g, with the optimal range being 1 g to 50 g. The wall thickness of these parts generally ranges from 0.5mm to 10mm.The wall thickness of these parts generally ranges from 0.5mm to 10mm. Therefore, this process is well-suited for manufacturing small, complex parts such as surgical instrument components and orthodontic brackets.
Die Casting: Part weights typically range from approximately 30 g to 50 kg. The wall thickness of die-cast parts ranges from 1.5 mm to 10 mm.This process can be used to manufacture medium to large structural components, such as camshaft covers, brake caliper brackets, and other automotive parts.
It is important to note that during the MIM sintering process, parts undergo linear shrinkage of approximately 15%–20%. Therefore, engineers must account for this shrinkage when designing parts.
Precision and Tolerances
Both processes have their own advantages in terms of precision. The key factor is the geometric complexity of the part. MIM is more suitable for manufacturing parts with complex three-dimensional features. While die casting is more suitable for manufacturing parts with simple geometry and tight tolerances.
MIM: The standard dimensional tolerance for this process is ±0.3% to ±0.5% of the nominal dimension. For example, for a part with a dimension of 20mm, the tolerance is approximately ±0.06mm to ±0.10mm. Furthermore, metal injection molding can produce parts with features such as internal threads, blind holes, and complex internal cavities in a single molding process.
Die casting: According to NADCA standards, the standard tolerance range for die-cast parts is ±0.1 mm to ±0.3 mm; however, the precision-level tolerance for die-cast parts can reach ±0.05 mm. Features such as hole positions and external dimensions require a high degree of precision.
Material Selection
Materials can be said to be the most fundamental difference between these two processes. Die casting is limited to non-ferrous metals with low melting points, whereas MIM can process virtually all metallic materials, including high-temperature alloys and difficult-to-machine materials.
MIM: Metal injection molding uses metal powder. Therefore, almost all metals that can be made into powder can be processed using this technique, including stainless steel, tool steel, titanium alloys, tungsten alloys, and more.
Die Casting: Materials that can be used for die casting include aluminum alloys, zinc alloys, magnesium alloys, and copper alloys. The aluminum enclosures you commonly see are generally manufactured through the die casting process. The range of material options for this process is relatively small.
Surface Finishing Options
The surfaces of parts produced by these two processes differ, which also determines the cost of subsequent surface treatment.
MIM: After sintering, the surface roughness of the parts is Ra 0.8 – 1.6 µm, which is superior to die casting. And because this process supports a variety of materials, there are many surface treatment options that can be chosen.
Die Casting: The surface roughness of die-cast parts ranges from Ra 1.0 to 3.2 µm. Die-cast parts have an excellent appearance but may exhibit parting lines and ejector pin marks. Therefore, these parts require various post-processing methods to improve their surface quality, such as sandblasting, anodizing, and CNC finishing.
Comparison Table of Other Items
| Criteria | Metal Injection Molding | Die Casting |
| Part Complexity | Very High | Moderate |
| Production Speed | Slow | Fast |
| Porosity | Very Low | Moderate risk |
| Material Density | 95–99% | 85–98% |
| Min. Production Volume | 1,000–5,000+ | 5,000–10,000+ |
| Lead Time | 8–16 weeks | 6–10 weeks |
Metal Injection Molding vs Die Casting Cost
As for comparing the costs of these two processes, I will conduct a comprehensive evaluation based on four factors: mold investment, unit cost, break-even point, and post-processing costs.
Mold Cost
| Cost Item | Die Casting | Metal Injection Molding |
| Mold Material | H13 Hot-work Tool Steel | P20 / H13 Steel |
| Mold Cost | $10,000 – $100,000+ | $5,000 – $50,000 |
| Mold Lifespan | 100,000 – 1,000,000 shots | 500,000 – 2,000,000 shots |
| Mold Modification Cost | High | Moderate |
- Because die-casting molds must withstand the impact of molten metal at high pressures and temperatures, they require higher-grade steel and are typically more expensive to manufacture.
- MIM molds are similar to plastic injection molding molds, with relatively lower processing difficulty and smaller initial investment.
Unit Cost and Batch Relationship
| Annual Volume | Die Casting Unit Cost | MIM Unit Cost |
| Under 1,000 pcs | Very High | High |
| 1,000 – 5,000 pcs | High | Moderate |
| 5,000 – 50,000 pcs | Moderate | Moderate |
| 50,000 – 100,000 pcs | Low | Low |
| Over 100,000 pcs | Very Low | Low |
Hidden Cost Analysis
MIM:
- Energy consumption costs of degreasing and sintering
- High cost of high-performance metal powder raw materials
Die casting:
- Die-cast parts require subsequent CNC machining
- Manual costs for deburring and trimming parting lines
- Low scrap recovery rate for aluminum/zinc materials
Metal Injection Molding vs Die Casting: Comparing Their Molds
The molds used in these two processes also differ. I will explain them to you one by one below.
MIM Mold
It is highly similar to molds used for plastic injection molding, consisting of two parts: the cavity plate and the core plate. MIM molds predominantly use cold runner systems. The location of the gate has a significant impact on feedstock, which also affects the dimensional consistency and density distribution of the sintered parts.
Because the injection pressure is much lower than that of die casting (typically 70–200 MPa), the impact and thermal stresses on molds used for metal injection molding are much smaller than those on die casting molds. In addition, injection molds are generally smaller in size and lighter in weight than die casting molds.
In addition, MIM molds are typically made from materials such as P20, H13, and S136, with a hardness requirement generally ranging from 28 to 35 HRC. Moreover, the mold has a low maintenance frequency and is relatively easy to repair.
Die Casting Mold
Die casting molds, also known as die tools. It mainly consists of two parts: the cover die and the ejector die. The interior of the mold contains a runner system, overflow wells, and venting channels. The ejection system inside the mold is responsible for removing the parts from the mold.
In addition, since die casting molds need to withstand high-pressure impacts, the mold structure must be very robust.
As for materials, die-casting molds are made of H13, H11 hot work tool steel, with a hardness requirement range of 44–48 HRC. These molds generally use vacuum quenching and tempering heat treatment. In addition, die-casting molds require very frequent maintenance. Furthermore, the maintenance frequency of die casting molds is very high.
Metal Injection Molding vs Die Casting: Application Comparison
There is also a significant difference between the two in terms of their applications. Die casting is more suited to large, high-volume structural components, while MIM is more suited to small, complex precision parts.
Automotive Industry
MIM: Metal injection molding process has a relatively low usage rate in the automotive industry. Typical parts include sensor housings, fuel injector components, etc.
Die Casting: The largest single market. Common die-cast car parts include engine blocks, cylinder head covers, transmission housings, and more.
Medical Industry
MIM: The medical industry is the fastest-growing and highest-premium market for MIM. Common medical components manufactured using this process include: endoscope components, bone screws and anchors, surgical instrument jaws, and more.
Die Casting: Die casting processes have limited applications in the medical industry, mainly used for manufacturing non-implantable device housings, such as Medical imaging equipment housings.
Aerospace Industry
MIM: Aerospace has extremely high requirements for material performance, and MIM technology possesses excellent high-temperature alloy processing capabilities. Common parts include turbine blade components, guidance system precision parts, and more.
Die Casting: In the aerospace industry, die casting is primarily used for non-critical structural components and interior trim parts.
Consumer Electronic
MIM: In the consumer electronics industry, metal injection molding is used to manufacture precision internal components.
Die Casting: Consumer electronics is the second-largest market for die casting. Components you encounter every day, such as laptop and tablet chassis and connector housings, are all manufactured using die casting.
Industrial Equipment
MIM: Typical parts include precision gear components, nozzle tips, and more.
Die Casting: Common parts include pump housings and impellers, valve seats, gearbox housings, and more.
Conclusion
The above is all the comparison content. I believe that after reading, you will have a clear understanding of the advantages and disadvantages of the two processes. Of course, there is no absolute distinction between good and bad processes. You still need to choose the most suitable process based on your actual application requirements. If you have any parts manufacturing needs, our DSR company can also provide you with die casting and metal injection molding services. Our engineers will communicate with you to ensure the processing feasibility of your projects.
FAQ
Q1: What is the future of metal injection molding?
A: Due to the growing demand for miniaturized, high-precision, high-performance metal parts in the medical device, aerospace, and new energy vehicle industries, the market for metal injection molding is steadily expanding at a compound annual growth rate of 8–12%.
Q2: Can MIM replace die casting for aluminum parts?
A: No. In the MIM process, aluminum powder is highly prone to oxidation during high-temperature sintering. And the core advantages of aluminum die casting process lie in large size, low cost, and high volume production.
Q3: Is MIM more expensive than die casting?
A: Overall, the unit original cost of MIM is higher, but the overall manufacturing cost may not be more expensive, especially when you need to manufacture structurally complex parts.
Q4: How accurate is injection molding?
A: The standard dimensional tolerances for parts typically range from ±0.3% to ±0.5%. For small precision parts, the tolerance can be controlled within ±0.05mm.
Q5: What are the disadvantages of metal injection molding?
A: 1. Limitations on part dimensions
2. High raw material costs
3. For small batch parts production, this process has low cost-effectiveness
Q6: What materials are used in metal injection molding?
A: Metal injection molding materials include the following:
| Material Category | Typical Grade |
| Stainless Steel | 316L, 17-4PH, 420 |
| Tool Steel | M2, H13 |
| Titanium Alloy | Ti-6Al-4V |
| Nickel Superalloy | Inconel 625 |
| Cobalt-Chrome Alloy | CoCrMo |
| Tungsten Alloy | W-Ni-Fe |
| Soft Magnetic Material | Fe-Si, Fe-Ni |
Q7: Can titanium be metal injection molded?
A: Yes. The titanium metal injection molding process is the most technically challenging.
Q8: How much does an injection molding machine cost?
A: The price range of metal injection molding machines is quite large. You can see the price comparison more intuitively from the following table.
| Equipment Type | Specification | Price Range (USD) |
| Entry-Level MIM Injection Machine | 50–100 tons | $30,000 – $80,000 |
| Mid-Range MIM Injection Machine | 100–300 tons | $80,000 – $300,000 |
| High-End Automated MIM Injection Machine | 300+ tons | $300,000 – $500,000+ |
