CNC Machining vs. Die Casting for Aluminum Housings: Which Process is Better?

Aluminum housings for electric vehicles (EVs), electronics, and automotive applications demand precision, lightweight construction, and durability. Two primary manufacturing processes—CNC machining and high-pressure die casting—are used to produce these components. Each offers distinct technical advantages and limitations, with the choice depending on production volume, dimensional requirements, and design complexity.

CNC Machining: Technical Overview

CNC machining uses computer-controlled tools to remove material from solid aluminum blocks, forming housings through milling, turning, or drilling. Key technical aspects include:

• Tolerances: Achieves tolerances as tight as ±0.005 mm, suitable for EV motor controller housings requiring precise mating surfaces.

• Material Properties: Typically uses aluminum alloys like 6061 or 7075, offering high strength (yield strength ~200-500 MPa) and excellent machinability.

• Surface Finish: Delivers Ra values of 0.4-1.6 µm, reducing the need for secondary finishing. Multi-axis CNC systems enable complex external geometries.

• Limitations: Material removal generates 30-50% waste by volume, increasing costs. Cycle times (e.g., 10-30 minutes per part) are slow for high volumes. Internal features, like deep cavities, require specialized tooling, raising complexity.

High-Pressure Die Casting: Technical Overview

Die casting injects molten aluminum (e.g., ADC12 or A380 alloys, with tensile strength ~300-350 MPa) into steel molds under pressures of 10-20 MPa. Key characteristics include:

• Production Efficiency: Cycle times of 30-60 seconds per part support high-volume runs (10,000+ units), ideal for EV battery enclosures.

• Design Capability: Produces thin walls (1-3 mm) and complex shapes, reducing weight (e.g., 20-30% lighter than machined parts). Mold designs incorporate cooling channels to control solidification.

• Tolerances and Finish: Achieves ±0.05-0.1 mm tolerances, often requiring secondary machining for precision fits. Surface roughness (Ra 1.6-3.2 µm) may show flash or porosity, necessitating post-processing like shot blasting.

• Limitations: Porosity from gas entrapment (1-2% by volume) can weaken parts. Mold development takes 4-6 weeks, limiting flexibility for design changes.

Comparative Analysis

• Low-Volume Production: CNC machining is ideal for 1-100 units, offering rapid setup (1-2 days) and adaptability for prototypes.

• High-Volume Production: Die casting is cost-effective for 1,000+ units, with per-part costs dropping to $1-5 versus $10-50 for CNC.

• Precision Needs: CNC machining suits high-precision EV components (e.g., tolerance <0.01 mm). Die-cast parts often require CNC finishing for similar accuracy.

• Complexity: Die casting excels for intricate, thin-walled designs; CNC machining is better for precise external features.

Conclusion

For aluminum housings, CNC machining offers superior precision and flexibility for low-volume or prototype needs, while high-pressure die casting provides efficiency and complex geometries for mass production. Combining die casting with CNC post-machining often optimizes cost, quality, and performance for EV applications.

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