Aluminum Die Casting vs CNC Machined Aluminum

Engineers face a genuine process choice between die casting and CNC machining for medium-complexity aluminum parts. Both produce precise aluminum components, but their economics diverge sharply as volume changes.

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Process Overview

Die Casting: Molten A380/ADC12 injected into hardened steel die. 30-120 second cycle time. Tooling cost $5,000-80,000; material utilization 70-75%; per-unit cost at volume is very low.

CNC Machining: Billet of 6061-T6 or 7075-T6 clamped in machining center; material removed by cutting tools. No tooling cost (fixtures only); material utilization 20-30%; per-unit cost is high but volume-independent.

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Full Comparison

Parameter	Die Casting	CNC Machining
Tooling cost	$5,000-80,000	$0-5,000 (fixtures)
Unit cost at 100 pieces	High	Competitive
Unit cost at 10,000 pieces	Very low	Much higher
Unit cost at 100,000 pieces	Extremely low	Prohibitive
Material utilization	70-75%	20-30%
Geometric complexity	High (slides for undercuts)	Very high (5-axis, few limits)
Min wall thickness	1.2 mm (Al)	0.3-0.5 mm
Dimensional tolerance	CT4-CT6 as-cast; ±0.02 mm machined	±0.005-1.05 mm
Surface finish	Ra 1.6-2.2 μm as-cast	Ra 0.4-0.6 μm
First article lead time	5- weeks (tooling first)	1- weeks
Alloys available	A380, ADC12, A360, A413	6061, 7075, 2024, any wrought
Mechanical properties	A380: 317 MPa tensile	6061-T6: 310 MPa; 7075-T6: 503 MPa

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The Volume Crossover Point

Example calculation:

• Die casting tooling: $15,000; unit cost: $3.50
• CNC machining tooling: $0; unit cost: $18.00
• Crossover: $15,000 / ($18.00 -$3.50) = 1,034 pieces

Above ~1,000 pieces total, die casting is more economical. At 10,000 pieces, die casting saves $145,000 versus machining. In practice the crossover falls between 500 and 5,000 pieces depending on part complexity.

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When to Choose CNC Machining

• Volume under 1,000 units lifetime: Avoid tooling investment
• Wrought alloy properties required: 7075-T6 (503 MPa) and 2024-T3 cannot be die cast
• Complex internal passages: Multi-axis or EDM produces tortuous passages die casting cannot form
• Short development timeline: Machined first articles in 1- weeks vs 5- weeks for die casting
• Very tight tolerances on nearly all features: If ±0.01 mm applies everywhere, machining may be more economical than extensive post-cast machining

When to Choose Die Casting

• Production volumes above 2,000-3,000 pieces
• Complex geometry with thin walls, fins, integrated bosses: Economical in die casting; expensive in machining
• Integrated thermal management: Fin arrays, cooling channels impossible to machine economically
• Single-source finished component: Casting + machining + finishing on one PO

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Prototype-to-Production Transition

Most products begin as machined prototypes and transition to die casting for production. Managing this well:

1. Design for both: Keep draft angle requirements and parting line placement in mind during prototype design
2. Use cast prototypes before production tooling: 50-100 pieces from P20 soft tooling validates casting behavior before H13 production tooling commitment
3. Expect dimensional differences: Cast and machined prototypes of the same design have different as-formed characteristics -evaluate cast prototypes against the drawing, not against the machined prototype

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Process selection consultation: yaoqingpu1983@gmail.com | +86 138 1403 4409