Overview

The RollerDrive RA series is a high-precision, zero-backlash servo reducer designed for factory automation equipment. It features a unique preload mechanism that eliminates backlash, ensuring precise and faithful output motion. The design emphasizes high torque, rigidity, stability, and compactness, making it ideal for precise motion control applications.

Key Technology: Zero-Backlash Mechanism

The core technology uses wedge-shaped ribs on the input shaft to preload roller followers, completely removing backlash. This preload is adjustable and the rolling contact transmission ensures high efficiency, wear resistance, and long-term accuracy retention.

Performance and Benefits

• High-precision motion: Fast settling times, precise positioning, and minimal speed fluctuation.
• Durability: Rolling contact bearings reduce wear and maintenance, lowering lifecycle costs.
• Compact design: Orthogonal input/output shafts and large hollow output shaft facilitate integration.
• Versatility: Suitable for high-accuracy positioning, alignment tables, rotary and pivot arm drives.

Mechanical Components

• Input Shaft: Alloy steel with advanced machining and balancing to suppress vibration at high speeds.
• Roller Followers: Rolling bearing structures transmit torque with permanent accuracy.
• Output Section: High-rigidity cross roller bearing minimizes deflection.
• Motor Coupling: Rigid connection with patented motor base absorbing mounting errors.

Specifications

Models include RA40, RA63, RA80, RA100, and RA125 with gear ratios from 15 to 30 (some made-to-order). Key parameters:

• Start/stop torque limits vary by model and lubrication.
• Maximum input speeds up to 3,000 rpm.
• Angular transmission accuracy typically ±60 to ±90 arc seconds.
• Angular repeatability ±5 to ±10 arc seconds.
• Specified permissible axial, radial, and moment loads.
• Weight ranges from ~2.5 kg (RA40) to >36 kg (RA125).
• Operating temperature: Max 60°C to prevent lubricant degradation.

Lubrication Options

• Grease lubrication: Standard, general use.
• Oil lubrication: Recommended for high-speed operation.

Lubrication choice depends on operating conditions. Expected service life is 12,000 hours within rated torque and speed curves.

Dynamic Rated Output Torque and Efficiency

Graphs show maximum allowable torque for 12,000-hour life, varying by gear ratio, lubrication, and speed. Oil lubrication supports higher speeds and torque. Efficiency charts indicate high transmission efficiency dependent on load, speed, and temperature.

Torsional Rigidity

Measured as shaft twist under load, torsional rigidity ranges from 2.8×10⁴ N·m/rad (RA40) to 74.4×10⁴ N·m/rad (RA125), indicating minimal deformation and high natural frequency.

Model Coding and Installation

Product codes specify model, size, gear ratio, lubrication, mounting position, motor mounting surface, attachments, and special instructions. Mounting positions are coded to indicate orientation. Servo motor installation is customer responsibility, with manuals provided. The motor shaft couples rigidly to the reducer input shaft, with the motor base absorbing mounting errors.

Compatible Servomotors

Supports servomotors from Yaskawa, Mitsubishi Electric, Panasonic, FANUC, KEYENCE, SANYO DENKI, and OMRON. Rated output power ranges from 0.2 kW to 5 kW depending on model. Servomotors must be prepared without keyways.

Critical Usage Notes

• Do not operate above 60°C to avoid lubricant degradation.
• Select lubrication based on speed and torque to ensure service life.
• Follow installation manuals for proper motor coupling and performance.
• Some gear ratios and lubrication types are made-to-order and require consultation.

Mechanical Specifications and Dimensions

Detailed dimensional data for RA series models include bore diameters, flange dimensions, mounting hole patterns, dowel hole positioning, and output table surface features. Oil-lubricated models have specified oil plug, level, and drain port locations with thread sizes and coordinates for maintenance.

Installation Guidelines

• Ambient temperature: +5°C to +40°C.
• Humidity below 85% without condensation.
• Avoid vacuum, high pressure, water, oil, chemicals, dust, explosive/hazardous gases, direct sunlight, shock, electromagnetic noise, and strong magnetic fields.
• Install on flat, rigid surfaces with correct orientation.
• Use lock-tightening agents (e.g., LOCTITE 242) and torque wrenches to tighten bolts to specified values.

Lubrication Instructions

• Oil lubrication uses high-performance lubricants (e.g., Mobil SHC629 VG150).
• Oil replacement every ~3,000 hours or if oil condition changes.
• Oil level checked via gauges when stopped; bubbles during operation are normal.
• Grease lubrication is generally maintenance-free; replacement coordinated with manufacturer.
• Oil and grease lubrication types are not interchangeable.

Tightening Torque Specifications

• Housing screws (aluminum alloy, DIN 6.8): M8 (18.5 Nm), M10 (36.0 Nm), M12 (63.0 Nm), M16 (158.0 Nm).
• Output flange screws (steel alloy, DIN 10.9): M5 (8.5 Nm), M6 (14.0 Nm), M8 (35.0 Nm), M10 (69.0 Nm), M12 (120.0 Nm).

Servomotor Mounting and Compatibility

Mounting dimension diagrams and tables specify motor base sizes, bolt hole patterns, shaft diameters, clamp collars, motor shaft sleeves, guide blocks, and associated bolts for secure motor attachment.

Shaft Rotation and Dowel Hole References

Input and output shaft rotation directions are consistently defined. Dowel holes on output table surfaces reference flange diameters and tapped holes; dowel holes on VW surfaces reference output shaft center and surface R for precise assembly alignment.

Oil Plug, Oil Level, and Drain Port Positions

For oil-lubricated models, detailed locations and thread sizes of oil plugs, oil levels, and drain ports on various surfaces facilitate maintenance.

Technical Performance Characteristics

• Backlash: Zero backlash achieved by preload mechanism, critical for servo accuracy.
• Lost Motion: Minimal torsion angle at rated torque midpoint, material-dependent.
• Hysteresis Loss: Residual torsion angle under forward/reverse torque, minimized by design.
• Angular Transmission Accuracy: 40 to 90 arc seconds or better, dependent on shaft machining precision.
• Dynamic Characteristics: Superior to traditional reducers and direct drive motors, with stable output speed and minimal disturbance under load.

Output Shaft Rotation Speed and Position

Graphs demonstrate stable, precise motion under various load conditions, confirming dynamic performance.

Unloaded Running Torque

Torque required at input shaft with no output load increases with speed due to lubricant viscosity; data provided for all RA sizes.

Protective Structure and Environmental Compatibility

Main unit protection rating is approximately IP54, offering dust and water ingress resistance but not full protection. Additional covers or treatments recommended for harsh environments.

Durability and Rated Service Life

Rolling contact design ensures minimal wear and stable accuracy over millions of cycles. Rated service life is 12,000 hours at 95% reliability, calculated based on load and torque ratios. Roller followers are manufactured in-house with high-quality materials.

Positioning Accuracy Over Time

Testing confirms stable forward/reverse exactness and repeatability over millions of cycles under specified load and speed conditions.

Usage Limitations and Environmental Conditions

• Not for use in life-critical, medical, nuclear, aerospace, explosive, corrosive, or toxic substance applications without consultation.
• Export control laws apply for weapon-related or overseas manufacturing uses.
• Operating ambient temperature range: 5°C to 40°C.

Technical and Legal Notes

• Specifications and product information subject to change without notice.
• Information current as of July 2012.
• All intellectual property rights belong to Sankyo Seisakusho Co., Ltd.

Contact and Global Network

Contact information for Sankyo Seisakusho and global offices in USA, China, Korea, Taiwan, Italy, Thailand, and regional offices in Japan is provided for sales and technical support.

Product Selection Sheet

A detailed selection sheet assists customers in specifying load conditions, environment, lubrication, servo motor specs, and mounting orientation for accurate product selection and customization.

Summary

The RollerDrive RA Series delivers high-precision, zero-backlash rotary motion with excellent dynamic response and long-term durability. Its advanced preload and rolling contact design minimize wear and maintain accuracy over millions of cycles. Protective features and detailed installation, lubrication, and compatibility guidelines ensure reliable operation in appropriate environments. Comprehensive technical data and global support facilitate effective integration into precision servo-driven applications.