Robot Joint
Housings

A robot joint housing is the structural enclosure of a robot axis joint — it holds the bearings, provides the interface for the reducer (harmonic drive, cycloidal, or planetary), and forms the structural connection between adjacent robot links. Its bearing bore, reducer seat, and output flange must all be concentric within a few micrometres for zero-backlash, smooth rotation.

Robot joint bearing bores: IT5 tolerance class — for angular contact bearings and cross-roller bearings used in robot joints, the bore must be K5 or M5 (slight interference with the bearing outer race) for a fixed outer race, or H5 for a rotating outer race. All bore tolerances are verified on the CMM and reported.

All critical concentric features — input bearing bore, output flange face, and reducer seat bore — are machined in a single 5-axis setup without rechucking. This eliminates the setup error that would occur in multi-operation machining, achieving concentricity ≤ 0.005 mm TIR between all features.

HXC has machined interfaces for all major robot reducer types: Harmonic Drive (HDSI, Ovalo, SPINEA); Cycloidal (Nabtesco, Sumitomo); Planetary (Neugart, Stober, Apex). Provide the reducer model number and we'll machine to the manufacturer's published interface drawing — no re-design needed.

Combining Al 7075 with internal pocket milling: 40–50% weight reduction vs a solid Al housing of the same envelope. Ti Grade 5 hollow housing: 30% lighter than Al solid with 60% higher specific stiffness — used in aerospace and high-performance collaborative robots.

The first-article CMM program (measuring all critical dimensions — bearing bores, flange faces, reducer seat, and inter-feature concentricity) is saved and re-run on 100% of parts in small batches and on a statistical sample basis for large production runs. Out-of-spec parts are quarantined before shipment.

Hard anodizing (Type III, 15–25 µm) on Al 7075 is standard — provides wear resistance on housing faces and corrosion protection, while only adding 15–25 µm to outside surfaces (not affecting bore tolerances, which are machined to compensate). Passivation is standard for SUS316L housings.

Prototype (1–3 pcs): 7–10 days. Small production batch (50–200 pcs): 12–18 days. Large production run: 18–28 days depending on complexity and CMM inspection load.