Introduction
Electric vehicle (EV) battery packs and power-electronics modules require protective enclosures that are strong, lightweight, thermally stable, and cost-efficient. Aluminum is the preferred material — but the manufacturing method you choose will determine performance and cost.
Two mainstream options are:
- CNC-machined aluminum enclosures
- Die-cast aluminum enclosures (with CNC post-machining)
Each method has strengths and limitations, and choosing the wrong one can lead to sealing issues, deformation, machining complications, or unnecessary cost.
This guide breaks down the differences and helps EV engineers and buyers select the right option.
1. CNC-Machined EV Enclosures: Precision and Flexibility
CNC machining removes material from a solid aluminum block (e.g., 6061 or 6063), creating a strong and highly accurate enclosure.
Key Advantages
➤ Highest dimensional accuracy (ideal for sealing surfaces)
➤ Fast prototyping and design adjustments
➤ Excellent material properties (no porosity)
➤ Ideal for small batches or early-stage EV development
➤ Better flatness and tight tolerances
Best Applications
➤ Battery pack prototypes
➤ Low-volume EV programs
➤ Critical sealing areas (O-ring grooves, gasket interfaces)
➤ Custom thermal-management housings
➤ Power-control units requiring precision fitment
Limitations
➤ Higher cost per unit
➤ Longer machining cycle time
➤ Material waste (machining from billet)
2. Die-Cast EV Enclosures: Cost-Effective for High Volume
Die casting injects molten aluminum (ADC12 / A380) into a mold, producing complex shapes with lower cost at scale.
Key Advantages
➤ Much lower unit cost for medium to high-volume production
➤ Complex shapes with integrated ribs, bosses, and features
➤ Lighter weight vs machined billet
➤ High repeatability once tooling is stable
Best Applications
➤ Mass-production EV battery housings
➤ Motor controller housings
➤ Inverter casings
➤ High-volume power-electronics enclosures
Limitations
➤ Requires CNC post-machining in critical areas
➤ Possible porosity inside material
➤ Dimensional stability depends on tooling quality
➤ High upfront tooling cost
➤ Longer development timeline
3. Structural Differences That Matter for EV Batteries
The choice between die casting and CNC machining directly affects:
Strength and rigidity
- CNC: superior material properties (no porosity)
- Die-cast: strength depends on casting density and design
Sealing performance
- CNC: excellent sealing due to precision
- Die-cast: sealing must be improved with CNC post-machining
Heat dissipation
- CNC: consistent thermal conductivity
- Die-cast: more variation based on material flow during casting
Weight optimization
- CNC: heavier due to solid billet
- Die-cast: integrates ribs for optimized weight
Design freedom
- CNC: limited by cutting tools
- Die-cast: extremely flexible for complex shapes
4. Cost Comparison: Which One Saves Money?
CNC Machining Cost Profile
➤ Higher per-unit cost
➤ Lower initial cost (no tooling)
➤ Best for 1–500 pcs
Die Casting Cost Profile
➤ High tooling investment
➤ Low unit cost at scale
➤ Best for 1,000+ pcs
For EV startups or prototype programs, CNC machining is usually the most cost-effective choice.
For mature battery platforms, die casting brings long-term savings.
5. Quality Considerations for EV Enclosures
Key areas EV buyers must inspect:
➤ Flatness of sealing surfaces
➤ CMM measurement for critical dimensions
➤ Porosity testing for die-cast parts
➤ Thread accuracy (machined after casting)
➤ Surface finishing stability (anodizing/painting)
➤ Tolerance stack-up across large housings
Typical issues and risks
- Die-cast parts may warp during cooling
- CNC parts may require large material removal
- Anodizing may cause slight deformation
- Poor machining strategies affect sealing
6. Which One Should You Choose? (Simple Decision Guide)
Choose CNC-Machined Enclosures If:
➤ You need prototypes or low-volume production
➤ Sealing performance is critical
➤ You need precise tolerance control
➤ Your design is still evolving
➤ Your internal space is tight and requires accuracy
Choose Die-Cast Enclosures If:
➤ You have stable annual volume (1,000+ pcs)
➤ You need complex ribbing and integrated features
➤ You want the lowest unit cost
➤ Some porosity is acceptable
➤ You can invest in tooling
Conclusion
Both CNC-machined and die-cast aluminum enclosures are essential in the EV industry — but each serves a different purpose.
- CNC is best for precision, prototypes, engineering validation, and small batches.
- Die casting is ideal for high-volume production with optimized cost and design flexibility.
Understanding the differences helps EV companies choose the right manufacturing method, reduce risk, and achieve better overall system performance.
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