Cycloidal Pinwheel RV Reducers

Cycloidal Pinwheel RV Reducers integrate a helical gear input and a cycloidal-pinwheel output stage. The input shaft drives eccentric crankshafts, which oscillate two cycloidal discs. Disc lobes mesh with stationary pinwheels (hardened steel pins inside a ring housing).

These Cycloidal Pinwheel RV Reducers are a type of speed reduction gear that utilize a unique cycloidal motion to achieve high reduction ratios in a compact design.

Cycloidal Pinwheel RV Reducers from TechMan Automation have four series as follows: 

RV-E Series: Main Bearing Built-in Type Cycloidal Gearboxes

RV-C Series: Hollow Type Cycloidal Pinwheel RV Reducers

RC-SC Series: Input Flange Hollow Type Cycloidal Gearboxes

RC-SE Series: Input Flange Type Cycloidal Gearboxes 

RV-N Series: Output Shaft Cycloidal Pinwheel RV Reducer

Cycloidal Pinwheel RV Reducers — Industrial Application Cases

Industrial Robotics:   6-axis welding robot — wrist joint drive

An RV reducer drives the J4 wrist joint of a 6-axis arc welding robot. Rated output torque is 380 N·m at a 161:1 reduction ratio. Input speed runs at 2,000 RPM from a 750 W servo motor. Output backlash measures below 1 arc-minute. Torsional stiffness reaches 490 N·m/arc-min. The cycloidal stage distributes tooth load across 66% of the pins simultaneously. This reduces peak Hertzian contact stress at each pin and extends the gear stage fatigue life beyond 12,000 hours. The RV hollow shaft routes the welding torch cable axially through the joint. Wrist repeatability holds ±0.02 mm at the TCP. No external cable management arm is needed. This reduces joint inertia by 0.18 kg·m² and lowers dynamic path error at corner velocities above 800 mm/s.

Ratio: 161:1      Output torque: 380 N·m        Backlash: <1 arc-min           Stiffness: 490 N·m/arc-min        TCP repeat: ±0.02 mm
WHY RV REDUCER
A planetary gearbox at this ratio requires two stages, doubling axial length and halving torsional stiffness. The RV single-body cycloidal stage delivers 161:1 in one housing. The hollow shaft eliminates the cable management arm — a component that adds 0.18 kg·m² of distal inertia and generates cable-drag torque that the servo must compensate on every path reversal.

Machine Tool: 5-axis machining centre — rotary B-axis tilt drive

An RV reducer drives the B-axis tilt table of a 5-axis vertical machining centre carrying workpieces up to 320 kg. Reduction ratio is 118:1. Peak output torque reaches 1,850 N·m during interrupted milling. Torsional stiffness is 1,240 N·m/arc-min. Output backlash is below 0.5 arc-minutes — equivalent to 0.0083° of angular error. At 500 mm workpiece radius, this produces 0.007 mm of positional uncertainty at the tool contact point. The RV crossed-roller output bearing carries the full 320 kg workpiece axial and radial load without a separate support bearing. Angular positioning error stays within ±3 arc-seconds under full cutting load. This meets ISO 10791-1 rotary axis accuracy Grade 1 for the B-axis.

Ratio: 118:1       Peak torque: 1,850 N·m      Backlash: <0.5 arc-min       Stiffness: 1,240 N·m/arc-min         ISO 10791-1 Grade 1
WHY RV REDUCER
Interrupted milling generates torque reversals at up to 80 Hz. A harmonic drive deflects elastically under this load, shifting the tool path by 0.015–0.025 mm. The RV cycloidal stage is 3–4× stiffer than an equivalent harmonic drive at this torque class. The integrated crossed-roller bearing eliminates the separate tilt-axis bearing housing, saving 95 mm of axial build height on the table column.

Semiconductor Equipment:   Wafer handler — θ-axis substrate rotation drive

An RV reducer drives the θ-axis of a 300 mm wafer handler inside an EFEM module. Reduction ratio is 81:1. Input comes from a 100 W brushless servo at 3,000 RPM. Output backlash measures below 0.8 arc-minutes. The RV hollow shaft — 40 mm bore — routes vacuum tubing and encoder cable axially to the end-effector without external routing. Total drive inertia at the output shaft is 0.0031 kg·m². The servo settles to ±0.005° within 180 ms after a 180° wafer rotation move. Wafer edge repeatability at 150 mm reach holds ±0.013 mm. The RV unit operates in a sealed grease configuration. Outgassing rate measures below 1 × 10⁻⁸ Pa·m³/s, meeting SEMI E21 atmospheric contamination limits inside the EFEM enclosure.

Ratio: 81:1      Hollow bore: 40 mm             Settle time: 180 ms                Repeat: ±0.013 mm                     Outgas: <1×10⁻⁸ Pa·m³/s
WHY RV REDUCER
SEMI E21 outgassing limits rule out standard gear oil lubrication. The RV sealed grease variant meets the contamination limit while delivering the 0.8 arc-minute backlash spec. A servo direct-drive at this joint reaches the repeatability target but requires a 22 Nm motor — seven times larger than the 100 W servo the RV enables — adding 340 g of rotating mass to the end-effector arm.

Collaborative Robotics:   Cobot elbow joint — J3 axis compact RV drive

A miniature RV reducer drives the J3 elbow joint of a 10 kg payload collaborative robot arm. Reduction ratio is 101:1. Rated output torque is 148 N·m. The RV unit outer diameter is 74 mm. Overall joint axial length is 52 mm. Input backlash measures below 1 arc-minute. Torsional stiffness is 216 N·m/arc-min. The RV cycloidal stage absorbs external impact loads up to 3× rated torque without tooth damage — a critical requirement for ISO/TS 15066 collaborative operation where unintended contact with operators must not cause joint failure. The hollow 28 mm bore routes joint power and signal cables axially. Cable fatigue life exceeds 10 million flexion cycles at ±180° joint range without cable management hardware outside the joint envelope.

Ratio: 101:1      Output torque: 148 N·m         OD: 74 mm                         Backlash: <1 arc-min                 ISO/TS 15066 compliant
WHY RV REDUCER
ISO/TS 15066 requires the joint to survive repeated impact overloads without positional drift. A harmonic drive flexspline cracks under cyclic impact above 2× rated torque. The RV cycloidal pins distribute impact load across multiple contact points simultaneously. This raises the single-event overload limit to 3× rated torque with no permanent deformation and no measurable change in backlash after 500 impact events.