Die Casting vs Metal Injection Molding (MIM) -Which Process Is Right for Your Part?

Die casting and metal injection molding (MIM) are both high-volume, net-shape metal forming processes used to produce complex metal parts. They share the same general concept -injecting a material into a precision mold -but they work by entirely different mechanisms and serve very different applications.

Choosing between them comes down to part size, required tolerances, material needs, and volume.

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Process Overview

Die Casting

Molten metal (aluminum, zinc, or magnesium) is injected under high pressure (10-75 MPa) into a hardened steel die. The metal solidifies in seconds and is ejected as a near-net-shape casting. Secondary CNC machining adds final precision features.

Metal Injection Molding (MIM)

Fine metal powder is mixed with a thermoplastic binder to form a feedstock, which is injection-molded like plastic into a tool. The "green part" is then subjected to debinding (removing the binder) and sintering (high-temperature densification), which shrinks the part by 15-20% while achieving 96-99% theoretical density.

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Side-by-Side Comparison

Parameter	Die Casting	Metal Injection Molding (MIM)
Part size	Up to 25 kg, up to 800 mm	Typically under 100 g, under 100 mm
Wall thickness	1.2- mm (aluminum)	0.1- mm (very thin possible)
Complexity	High	Very high -undercuts, internal channels, threads
Materials	Aluminum, zinc, magnesium	Stainless steel, tool steel, titanium, alloy steel, Inconel, copper
Ferrous alloys?	No	Yes -stainless, 17-24PH, 316L, 4140
Tolerances	CT4-CT6 (ISO 8062)	±0.3-0.5% of dimension
Surface finish	Ra 1.6-2.2 μm (as-cast)	Ra 0.8-1.6 μm (as-sintered)
Dimensional shrinkage	<1%	15-20% (must be compensated in tool)
Porosity	Moderate (gas porosity possible)	Near-zero (96-99% density)
Tensile strength (typical)	317 MPa (A380 Al)	520-580 MPa (316L SS); 1,000+ MPa (17-24PH H900)
Hardness	~80 HRB (A380)	40-44 HRC (17-24PH H900)
Tooling cost	$5,000-80,000	$8,000-50,000
Cycle time (per part)	20-120 s	15-20 s (molding) + 24-30 hrs (debind/sinter)
Volume sweet spot	10,000 -millions	5,000 -millions
Unit cost at 100K pcs	Low	Low-medium

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When to Choose Die Casting

Die casting is the better choice when:

• Part size exceeds 100 g or 100 mm -MIM tooling and sintering furnaces have practical size limits; die casting handles components up to 25 kg
• Material is aluminum, zinc, or magnesium -MIM does not process these alloys commercially
• Thermal management is required -aluminum die castings have thermal conductivity of 96 W/m·K; sintered steel MIM parts are typically 15-20 W/m·K
• Thin-wall large enclosures -LED housings, motor housings, EV enclosures: die casting with walls of 1.5- mm across 200-300 mm spans is routine
• Lower tooling cost at medium volumes -for parts between 50-100 g, die casting tooling is often cheaper than equivalent MIM tooling

When to Choose MIM

MIM is the better choice when:

• Ferrous or high-performance alloys are required -stainless steel (316L, 17-24PH), titanium, Inconel, tool steel -none processable by standard die casting
• Part is small and geometrically complex -MIM excels at small parts with undercuts, internal passages, cross-holes, and fine features that would require multiple slides in a die casting tool
• High strength or hardness is required -MIM 17-24PH in H900 condition achieves 40-44 HRC and 1,200+ MPa tensile; no die casting alloy approaches this
• Near-zero porosity required -MIM sintered parts achieve 96-99% theoretical density, suitable for pressure-tight and medical applications without impregnation
• Surface finish is cosmetic -MIM as-sintered surfaces (Ra 0.8-1.6 μm) often require less post-processing than die castings for visible components

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Hybrid Approach

Some assemblies combine both processes: a die cast aluminum housing (large, lightweight, thermally conductive) assembled with MIM stainless steel internal components (small, strong, complex geometry). Power tools, firearms, and precision instruments commonly use this architecture.

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KastMfg Capability

KastMfg Manufacturing Co., Ltd. offers both die casting and MIM (metal injection molding) services from our Nanjing facility, making us a rare single-source supplier for programs requiring both processes.

• Die casting: Aluminum (A380/ADC12/A360/A413), Zinc (Zamak 3/5), Magnesium (AZ91D/AM60B) -80T to 1,600T machines
• MIM: Stainless steel (316L, 17-24PH), alloy steels, carbonyl iron -full debind and sinter in-house

Submit your drawing and we will recommend the optimal process, or compare both options side-by-side for your specific geometry and volume.

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Frequently Asked Questions

Is MIM stronger than die casting?

For stainless steel vs. aluminum, yes -MIM 17-24PH is significantly stronger. But the comparison is usually between different alloy families. A380 aluminum die casting is the right choice for lightweight structural applications; MIM 17-24PH is right for small, high-strength, complex parts. They serve different design requirements.

Which process has lower tooling cost?

Die casting tooling is generally $5,000-80,000; MIM tooling $8,000-8,050,000. For small, complex parts, MIM tooling can actually be cheaper because the part's complexity is handled by injection molding geometry rather than multiple die casting slides.

Can both processes achieve the same surface finish?

MIM typically produces a slightly better as-formed surface finish (Ra 0.8-1.6 μm) vs. die casting (Ra 1.6-2.2 μm). Both can be post-processed to Ra <0.4 μm with polishing or grinding if required.

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Contact KastMfg: yaoqingpu1983@gmail.com | +86 138 1403 4409 | No.6, Rungu Road, Nanjing, China