Scratch-free anodized aluminum sleeves: 5,000 pcs in 20 days
By NOW CNC · Production case study · Published · Updated 
Reviewed by Xiujuan Wang, Quality Supervisor
Laser equipment · 6061-T6 aluminum · Ø40 × 120 mm · 5,000 pcs · CNC turning + outsourced anodizing
At a glance
| Material | 6061-T6 aluminum |
|---|---|
| Size | Ø40 mm OD × 120 mm long |
| Quantity | 5,000 pcs |
| Finish | Standard anodizing, 15 µm |
| Cosmetic requirement | No visible scratches at 300 mm under normal lighting |
| Inspection | 100% visual inspection |
| Lead time | 20 days from order, including anodizing trials |
| Delivered |
The challenge
The machining itself was straightforward. The difficulty was the surface: this laser equipment part could not show a single visible scratch after anodizing. Scratches can happen at any step: during machining, in handling between operations, and at the anodizing supplier. Anodizing is outsourced, so part of the risk sat outside our own factory.
Protecting the surface in our workshop
We turned the sleeves on CNC lathes. After final machining, every part went straight into its own custom foam cavity so that no two parts touched. Every part was inspected. With this handling in place, we brought our in-house cosmetic reject rate down to 1%.
Qualifying the anodizing supplier before production
We expected the anodizing step to be the biggest risk, so we tested it before running the full 5,000 pieces. We sent 50-piece trial batches to three anodizing suppliers, each with the same written cosmetic requirement.
| Anodizing supplier | Trial quantity | Cosmetic reject rate |
|---|---|---|
| Supplier A | 50 pcs | 70% |
| Supplier B | 50 pcs | 10% |
| Supplier C | 50 pcs | 50% |
| Supplier B, second trial | 100 pcs | 3% |
Have a cosmetic anodized part? Send a drawing
Our quality team worked closely with Supplier B on the causes of the rejects, then ran a second 100-piece trial. The reject rate fell to 3%. The unit cost rose slightly, but because we had planned extra material from the start, the trials did not delay delivery.
Inspection and packaging
Every finished part was checked by eye at 300 mm under normal lighting, and any part with a visible scratch was rejected. Rejects were labeled and kept apart from accepted parts. Accepted parts shipped in individual foam cavities.
Photographs show the same part at our factory.
Result
5,000 sleeves delivered 20 days after the order, including the anodizing trials.
What this means for your cosmetic parts
For parts with cosmetic requirements, we run trial batches at the finishing supplier before production.
For anodized parts with cosmetic requirements, the risk is usually in finishing and handling, not in the machining. Two things to ask any supplier:
- How will you qualify the anodizer before production?
- How will parts be protected between machining, finishing and packing?
On your drawing, state the viewing distance, lighting and what counts as a visible defect, so that everyone inspects to the same standard.