Case Study — Medical / Senior Wearable
When a US senior-wearable brand came to us, they had a problem most CNC suppliers had waved away: they needed a deep-black aluminum watch housing that could sit on an elderly wrist all day — and pass ISO 10993 skin-contact biocompatibility testing. They had already tried three coatings. None gave a clean answer.
Eight months later, we had delivered 6,000 units and all three ISO 10993 tests had passed. Here's exactly how.
The Part
● Industry: Medical / senior wearable device
● Part: CNC aluminum watch housing (lower case)
● Material: 6061-T6 aluminum alloy
● Volume: Sample → 250 → 6,000 pcs
● Final finish: E-plating + ceramic black
● Compliance: ISO 10993-5, -10, -23 (skin contact)
The Problem — Does This Sound Familiar?
"Which coating actually passes ISO 10993?" The client had already burned time on Parylene C, DLC and PVD without a clean result. We ran a structured comparison and guided every decision — landing on e-plating + ceramic black.
"The coating looks great, but it won't bond to the VHB adhesive inside." We engineered precision masking for the adhesive zone. No re-work.
"After bead blasting, the threaded holes clog and screws won't go in." We added rubber-plug masking before blasting. Zero clogging across the run.
"I need documentation — SDS, CoC, chemical composition." We provided RoHS, REACH and Halogen reports, and coordinated the ISO 10993 testing end to end.
Coating Selection — We Tested So They Didn't Have To
Six iterations across five coating systems, looking for deep black + premium feel + full biocompatibility:
Anodizing + Parylene C
● — Rejected. Good black and biocompatible, but poor adhesion on metal, delamination, blurred masking edges.
DLC (matte/gloss)
● — Partial. ISO-compatible and scratch-resistant, but grayish and bead blasting filled the threads.
PVD
● — Rejected. ISO-compatible and hard, but grayish-black, not premium, higher cost.
Ceramic black (alone)
● — Partial. Visible black and cost-effective, but rough texture with visible tool marks.
E-plating + ceramic black
● — ✅ Selected. Deep pure black, smooth premium feel, fingerprint-resistant, ISO 10993 all-pass.
Timeline — Sample to 6,000 Units (Sep 2025 – Apr 2026)
Sep 2025
● — First inquiry and technical review; flagged coating and adhesion risks upfront.
Sep–Oct 2025
● — Sample production and coating trials; four coating systems compared.
Nov–Dec 2025
● — First batches delivered; three new coatings tested side by side for the premium finish.
Jan–Mar 2026
● — Bulk production and reorders; grew to 6,000 units across four batches, zero critical defects on certified units.
Apr 2026
● — ISO 10993: all three tests passed. Official report by accredited lab (CTI, Centre Testing International).
ISO 10993 Biocompatibility — All Three Passed
ISO 10993-5 — Cytotoxicity:
● MEM elution, L929 cells. PASSED.
ISO 10993-10 — Skin Sensitization:
● Magnusson-Kligman method. PASSED.
ISO 10993-23 — Skin Irritation:
● Intradermal, ISO standard. PASSED.
We ran all three tests in parallel, saving roughly 42 days versus sequential testing. Testing was performed by CTI (Centre Testing International), a leading accredited third-party lab. We coordinated sample prep, submission and the full documentation package — so the client didn't have to manage the lab process alone.
Three-Stage Quality Control
Before bead blasting:
● dimensional check on key features, rubber plugs into every threaded hole, masking verified against the drawing.
Before ceramic coating:
● e-plating base layer inspected, surface cleanliness verified, VHB adhesion zones masked and confirmed.
Pre-shipment:
● 100% visual inspection, screw-in test on threaded holes, photo and video before packing.
No black boxes — the client saw the parts before they shipped. That's how a 6,000-unit run ships with zero critical defects.
Working on a similar part?
If your product touches skin, needs a specific finish, or requires ISO 10993, this is exactly what we do. When you reach out you get:
● Free feasibility (DFM) review of your 3D file and specs
● A coating recommendation for your application
● A sample quote within 24 hours
● Full documentation (RoHS, REACH, CoC)
Send us your drawing — we'll tell you honestly what's possible.
Shenzhen Tingfeng Hardware Products Co., Ltd. | tingfengprecision.com | Alibaba: sztfeng288