Planetary micro-gearbox RP28

coaxialsolid-shaftkeyed shaft

Product overview
RP28 is a 28 mm planetary gear motor / gearbox designed for industrial and precision applications such as high-load electric valves, robotic drives, and medical devices. The gearbox features a 28 mm outer diameter, ball-bearing supported output, and multiple gear ratio ranges. Rated torque reaches 1.0 N·m with momentary peaks up to 3.0 N·m.

Key facts for engineering buyers

• Product category: Planetary gear motors & gearboxes
• Motor family: Planetary gear motor / gearbox
• Brand / manufacturer: KWC Motor, Dongguan KWC Machinery Co., Ltd.
• Typical applications: high-load electric valves, robotic arms, medical equipment

Core applications & solutions

• Industrial automation & electric valves: Suitable for fluid control valves, damper actuators and vending machines. Ball-bearing output supports stable transmission under frequent start/stop cycles and high side loads; rated torque up to 1.0 N·m.
• Robotics & precision motion: Used in inspection robot wheel-hub drives, medical peristaltic pumps and rotating advertising displays. Can withstand momentary shock torque up to 3.0 N·m to protect equipment during overload events.

RP28 gearbox technical specifications
Gear Ratio | Stages | Length L (mm) | Rated Torque | Max Momentary Torque | Efficiency
1/4 ~ 1/5 | 1 | 23.3 ±0.5 | 0.1 N·m | 0.3 N·m | 90%
1/16 ~ 1/25 | 2 | 29.0 ±0.5 | 0.4 N·m | 1.2 N·m | 81%
1/64 ~ 1/125 | 3 | 34.7 ±0.5 | 0.8 N·m | 2.4 N·m | 73.9%
1/256 ~ 1/625 | 4 | 40.4 ±0.5 | 1.0 N·m | 3.0 N·m | 66%

Mechanical parameters

• Gearbox outer diameter: 28 mm
• Shaft diameter: 6 mm (D-shaft flat: 5.5 mm)
• Output shaft supported by ball bearings
• Maximum radial load: 50 N
• Maximum axial load: 30 N

Customization and sourcing notes

• OEM/ODM customization available for voltage, speed, torque, shaft design, cable/connector, gearbox integration and control requirements
• Compatible with 28 mm series motors (e.g., RS-385/395) in brushed or brushless versions
• Output shaft options: 6 mm shaft with keyway, thread or double-flat profiles; shaft length and features customizable
• Supports momentary torque up to 3.0 N·m for high-startup torque applications

Design features

• Ball bearings: increased radial and axial load capacity compared with sleeve bearings
• Powder-metal gears: high-density gear material providing wear resistance and impact strength
• Press-fit validation: shaft center validated for press-in forces up to 60 N
• Compliance: RoHS / REACH

Characteristics / technical summary

• Model / Series: RP28
• Outer diameter: 28 mm
• Shaft diameter: 6 mm (D-flat 5.5 mm)
• Available gear ratio ranges: 1/4~1/5, 1/16~1/25, 1/64~1/125, 1/256~1/625
• Stages: 1, 2, 3, 4
• Lengths L (mm): 23.3 ±0.5, 29.0 ±0.5, 34.7 ±0.5, 40.4 ±0.5
• Rated torque: 0.1 N·m (1-stage) to 1.0 N·m (4-stage)
• Max momentary torque: up to 3.0 N·m
• Efficiency by stage: 90%, 81%, 73.9%, 66%
• Maximum radial load: 50 N
• Maximum axial load: 30 N
• Bearing type: ball bearings (standard)
• Materials / features: powder-metal gears, press-fit validated shaft center