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In robotics, surface finish is never just a cosmetic detail. It decides how quietly a gear meshes, how reliably a bearing seats in its housing, and how long the whole joint runs before wear starts to eat into positioning accuracy. So what surface finish can robotics CNC machining actually achieve on gear and housing parts? The short answer: standard CNC milling and turning routinely deliver Ra 3.2 μm, fine machining reaches Ra 0.8 μm, and secondary processes such as precision grinding and polishing push critical surfaces down to Ra 0.4–0.2 μm. Below is a practical breakdown of what is achievable on each feature of a robot gear and housing, and how to specify it without overspending.
Different processes top out at different roughness levels. Knowing the ceiling of each one helps you match the right process to the right feature:
| Process | Achievable Ra | Typical Use on Gears & Housings |
|---|---|---|
| CNC milling / turning (standard) | Ra 3.2 μm | General housing faces, non-critical gear features |
| CNC milling / turning (fine) | Ra 1.6–0.8 μm | Bearing seats, gear bores, mating surfaces |
| Precision surface grinding | Ra 0.4 μm (Ra 0.2 μm with polishing) | Gear tooth flanks, precision mounting faces |
| Wire EDM | Ra 0.8 μm | Hardened gear profiles, keyways, fine slots |
| Honing / lapping / polishing | Ra 0.4–0.2 μm and below | Precision bores, mirror-finish sealing surfaces |
Gears are the most finish-sensitive components in a robot drivetrain, because every roughness peak on a tooth flank becomes a source of friction, noise, and micro-pitting once the joint starts cycling.
Housings carry bearings, seals, and mating flanges, so each feature class has its own finish requirement:
When machining alone cannot reach the target, secondary processes close the gap. Bead blasting evens out tool marks into a uniform matte texture. Electropolishing can bring a stainless steel gear surface down toward Ra 0.4 μm while improving corrosion resistance. Hard coatings such as TiN or DLC add surface hardness and lower friction on heavily loaded flanks. For aluminum housings, anodizing adds wear and corrosion protection, but the coating growth has to be accounted for on tight-tolerance features — a shop with in-house coating and surface treatment capability can hold dimensional change under 5 μm and mask the surfaces that must stay as-machined.
Surface finish is one of the fastest ways to inflate a machining quote if it is specified carelessly. A few rules of thumb keep cost under control:
ANOK Precision Manufacturing is an ISO 9001:2015 certified factory in Shenzhen specializing in custom precision parts for automation and robotics. Our shop holds tolerances down to ±0.002 mm, with surface grinding reaching Ra 0.4 μm (mirror polish to Ra 0.2 μm), wire EDM at Ra 0.8 μm for hardened gear steels, and full in-house anodizing, electroplating, and polishing. We machine everything from aluminum 6061/7075 and stainless steel to titanium alloys and PEEK, so your gears and housings get the finish their function actually demands.
Send us your drawings with the surface finish callouts — or just tell us how each surface is used — and our engineers will return a quote with DFM feedback on the most cost-effective way to hit every specification.