Metal injection molding (MIM) is ideal for producing small, intricate, high-strength parts with tight tolerances, whereas high pressure die casting is a faster, more cost-effective solution for mass-producing non-ferrous metal components. The choice between these two processes depends on part complexity, performance needs, applications, and budget.
This article delves into how these manufacturing processes work, their material compatibility, benefits, limitations, and key selection criteria. Read on to determine the best fit for your project.
Metal Injection Molding (MIM)
Process Overview
MIM combines plastic injection molding with powder metallurgy.
Fine metal powder is mixed with a thermoplastic binder to form a feedstock, which is then heated and injected into a mold under high pressure to create a “green body.”
The green body undergoes a debinding process to remove the binder before being sintered at high temperatures (typically 1200-1400°C).
This sintering process densifies the part to 95-99% of its theoretical density, yielding a high-strength component with excellent performance.
Materials Used
MIM is compatible with various high-strength metals and alloys, including:
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Stainless Steels: 316L, 17-4PH, 304, 440C
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Titanium Alloys: Ti-6Al-4V, Ti-5Al-2.5Sn
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Nickel Alloys: Inconel 718, Hastelloy X, Monel K500
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Tool Steels: M2, D2, H13, S7
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Tungsten and Cobalt Alloys: WC-Co, W-Ni-Fe, W-Ni-Cu
Key Benefits
- Complex Geometries: Enables intricate shapes, thin walls, undercuts, and internal passages that are challenging for machining or casting.
- High Mechanical Strength: Near-full density ensures excellent strength, toughness, and wear resistance, comparable to wrought metals.
- Near-Net Shape Manufacturing: Minimizes or eliminates secondary processing, reducing costs.
- Consistency and Repeatability: Delivers tight tolerances (typically ±0.3% of nominal size) and uniform mechanical properties.
Limitations
Size Constraints: Best suited for small to medium-sized parts (under 100 grams); larger parts may experience shrinkage and distortion during sintering.
Higher Cost for Large Volumes: More economical for medium to large production runs of small, complex parts, but generally costlier per unit compared to die casting process for mass production.
Longer Production Cycles: The multi-step process (molding, debinding, sintering) takes longer than die casting aluminum.
Industry Applications
MIM is suitable for parts that require high precision, small, complex geometries, and high strength requirements:
- Medical Devices: Dental brackets, surgical instruments (vascular clips, forceps), endoscope parts.
- Aerospace: Fuel nozzles, control valve cores, cabin locking components, high-strength hinges.
- Electronics: Smartphone hinges, TWS (true wireless Bluetooth headset) metal parts, battery connectors.
- Firearms: Trigger assemblies, safety components, magazine catches, hammers.
- Automotive: Injector components, EPB actuator gears, ABS brake system parts, turbocharger blades.
Die Casting
Process Overview
Die casting is a high-pressure casting process where molten metal is forced into a steel mold under high pressure.
The metal solidifies rapidly, and the part is ejected once cooled. This method enables the mass production of metal parts with consistent quality and precision.
There are two primary die casting methods:
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Hot Chamber Die Casting
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Cold Chamber Die Casting
Materials Used
Aluminum die casting materials primarily employ non-ferrous metals, such as:
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Aluminum Alloys: A380, ADC12, AlSi10Mg, A356
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Zinc Alloys: Zamak 3, Zamak 5, ZA-8, ZA-12
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Magnesium Alloys: AZ91D, AM60B, ZK60A
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Copper-Based Alloys: Brass C85700, Bronze C83600, CuZn39Pb3
Main Advantages
- High Production Efficiency: Fast cycle times, with each part forming in seconds, ideal for large-scale production.
- Cost-Effectiveness: Despite high mold costs, low unit costs make die casting products preferable for mass production.
- Good Surface Quality: Die casting foundry parts usually have a smoother surface and can be used directly or only require a small amount of surface treatment, such as sandblasting or powder coating.
Limitations
Limited Geometric Complexity: Unlike MIM, aluminium die casting has difficulty handling highly detailed, complex designs, especially those that require undercuts or thin walls.
Porosity Issues: High-pressure injection can trap air, creating porosity that weakens parts’ mechanical properties.
Additional Machining: Die casting products have good dimensional accuracy, but are not as good as MIM parts.
For parts with tight tolerance requirements, subsequent CNC finishing is still required to achieve final specifications.
Industry Applications
Aluminum die casting is suitable for medium and large parts that need to be mass-produced, and have relatively simple shapes, uniform wall thickness, and moderate dimensional accuracy requirements:
- Automotive Parts: Engine blocks, gearbox housings, clutch housings, brake cylinder housings.
- Consumer Electronics: Laptop housings, smartphone metal frames, camera bodies, smartwatch cases.
- Industrial Equipment: Motor housings, hydraulic valve bodies, compressor housings, turbine impellers.
- Household Appliances: Gas stove bases, washing machine drive wheels, vacuum cleaner housings, electric fan bases.
In-Depth Comparison of MIM and Die Casting
Materials
MIM supports a broader range of ferrous and high-performance alloys, while aluminium die casting is limited to non-ferrous metals like aluminum and zinc.
Part Shapes
MIM enables highly complex designs, including thin walls and intricate internal channels.
Aluminum die casting is more suitable for medium and large components but struggles with fine details and internal voids.
Dimensional Accuracy
MIM achieves superior tolerances and smoother surface finishes, reducing secondary processing.
Die casting aluminum often requires additional machining and polishing to meet strict dimensional and cosmetic standards.
Productivity
High pressure die casting offers faster cycle times, making it ideal for high-volume production.
MIM takes longer due to its debinding and sintering steps.
Cost-Effectiveness
Both require expensive molds, but die casting foundry molds last longer.
Aluminium die casting is more economical for high volumes, while MIM is cost-effective for small, complex parts.
Strength
MIM parts achieve high density through high-temperature sintering, avoiding porosity defects common in die casting process, and form a metallurgical bond that makes their strength and mechanical properties better than die casting products.
Sustainability
MIM generates minimal waste as excess powder is recyclable. Aluminium die casting produces more scrap due to flash and trimming.
Additionally, die casting foundry processes have higher energy consumption due to metal melting and rapid cooling, whereas MIM has a lower carbon footprint, especially in small-batch production.
Conclusion
MIM and die casting processes each have unique advantages depending on application requirements.
MIM excels in small, high-precision components requiring superior strength and material versatility, while high pressure die casting is ideal for large-scale production of non-ferrous metal parts with cost advantages and faster cycle times.
The best process depends on part complexity, performance needs, applications, and budget.
Contact us today to discuss your project, and let our expertise help you choose the best solution for your needs.