The reducer shaft is a core transmission component of RV and harmonic reducers, undertaking the critical functions of torque transmission and positioning support. Its shaft journals, splines, oil holes and mating grooves require high precision with strict control over surface roughness and geometric tolerances. The joints of humanoid robots frequently start and stop and bear alternating loads during forward and reverse rotation within a compact operating space. If cutting oil, grinding fluid, micron-sized metal debris or polishing paste residue remains on the shaft surface, it will easily lead to gear surface wear, bearing seizure, transmission torque fluctuation, abnormal noise and heat generation of the reducer. This directly shortens the service life of the reducer and undermines the repeat positioning accuracy and motion smoothness of the robot’s walking and grasping movements. Traditional cleaning methods such as spraying and conventional ultrasonic cleaning cannot reach blind spots at spline roots, micropores and narrow gaps. They suffer from inconsistent cleaning results, may scratch precision working surfaces, and leave watermarks and oxidation after drying, failing to meet the high cleanliness requirements for mass production of humanoid robot reducers.

Focused on the cleaning of precision transmission components, Buck has developed a dedicated vacuum ultrasonic cleaning solution for humanoid robot reducer shafts to tackle cleaning challenges in hidden areas including splines, inner holes and oil grooves. The integrated process consists of vacuum ultrasonic degreasing, high-frequency ultrasonic fine cleaning, multi-stage ultra-pure water rinsing, and vacuum/nitrogen drying. Air trapped in gaps and micropores is removed under vacuum to eliminate the bubble shielding effect, enabling ultrasonic cavitation energy to fully reach all concealed areas. Stubborn oil contaminants and micro-particles are gently stripped away. There is no rigid contact throughout the process, so the high-gloss surfaces of shaft journals and spline tooth flanks remain intact, and the geometric tolerances and surface roughness of workpieces are preserved.

The equipment chamber is made of 316L stainless steel with electropolished pipelines. Equipped with a multi-stage circulating filtration and oil-water separation system, it continuously intercepts metal powder and oil sludge to avoid secondary contamination during cleaning. Ultrasonic frequency, cleaning temperature, soaking cycle and rinsing times can be programmed via PLC. It adapts to harmonic and RV reducer shafts of different materials and specifications and supports flexible mixed production of multiple models. Cleaned parts consistently meet the technical cleanliness standards of VDA19 and ISO16232 with controllable particle residues. No water stains or oxidation spots form after drying, and the workpieces are ready for assembly immediately after cleaning.

Buck cleaning systems support automated integration. They can be fitted with gantry manipulators and loading/unloading fixtures and connected to the production line MES system to realize fully automatic cleaning, drying and unloading. The cycle time matches machining, inspection and assembly processes, greatly reducing secondary contamination caused by human contact and steadily improving the yield rate.

In the industrialization of humanoid robots, the reducer serves as a core joint component, and cleanliness acts as a key indicator determining the reliability of the whole machine. Buck’s vacuum ultrasonic precision cleaning solution delivers stable and reproducible cleanliness assurance for core transmission parts of humanoid robots such as reducer shafts, crankshafts and gear shafts. It reduces the risk of early reducer failure, enables long-term stable operation of robot joints, and supports high-quality large-scale delivery of reducer production lines.