CNC Milling · Prototype
Selective Machining After Black Anodizing on an Aluminum Prototype
A prototype needed bare, uncoated aluminum in specific areas with no masking marks — solved by anodizing first, then precision-locating the part for secondary machining.
At a Glance
- Material
- Aluminum alloy
- Process
- CNC milling, black anodizing, selective secondary machining
- Requirement
- Clean bare-aluminum areas, no anodize, no contamination
01
The Challenge
The drawing called out specific areas that had to remain bare aluminum — no black anodizing, no contamination, and a clean, presentation-ready appearance. Masking those areas before anodizing was the obvious route, but masking typically leaves uneven edges and witness marks that would not meet the appearance requirement, and the affected surfaces still needed tight dimensional control.
02
OUJI's Approach
OUJI anodized the part first as a complete black part, then precision-located it in a second machining setup to remove the coating from only the specified surfaces. Locating datums and fixturing were planned around the finished part geometry so the secondary cut removed exactly the coated layer without disturbing the surrounding anodized surfaces or the underlying dimensions.
03
The Result
The prototype met the customer's dimensional and appearance requirements, with clean, sharp transitions between the anodized and bare-metal areas — without the uneven edges or witness marks that masking would have left.
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