Scheduled Maintenance for R-50/R-100 Series J2/J3 Axes using the 762-001 Joint Overhaul Kit

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Tools Required

• Torque wrench (Nm scale)
• Metric hex key and socket set
• Bearing puller set
• Seal installation tool
• Soft mallet
• Grease gun
• Lint-free cloths
• Non-residue solvent cleaner
• Mechanical support stands or overhead crane

Article

This document outlines the standard procedure for overhauling the J2 (waist) and J3 (shoulder) axes on NexBot Robotics R-50 and R-100 series articulated robots. This maintenance is recommended every 8,000 operational hours to address component wear, reduce backlash, and restore original positioning accuracy. The procedure utilizes the comprehensive NexBot Robotics 762-001 Joint Overhaul Kit (NXB-KIT-762-001), which contains all necessary OEM replacement components.

Performing this maintenance correctly is critical for robot longevity and performance. It should only be attempted by certified technicians familiar with NexBot robot mechanics and safety protocols.

Safety Precautions

WARNING: Failure to follow safety procedures can result in serious injury or death, and damage to the equipment. Always consult the robot's primary safety manual before beginning any maintenance.

• Lockout/Tagout (LOTO): De-energize and lock out all power sources (electrical, pneumatic, hydraulic) to the robot and controller according to your facility's safety standards.
• Mechanical Hazards: Ensure the robot arm is mechanically secured or resting in a stable, fully supported position to prevent unexpected movement or collapse.
• Personal Protective Equipment (PPE): Wear appropriate PPE, including safety glasses, steel-toed boots, and gloves.

Schedule

• Interval: Every 8,000 hours of robot operation.
• Condition-Based: This maintenance should also be considered if the robot exhibits symptoms of excessive backlash, positioning inaccuracy alarms, or audible noise from the J2 or J3 joints.

Parts and Tools Needed

Parts

• NXB-KIT-762-001 Joint Overhaul Kit, which includes:
• Wave Generator Assembly
• Flexspline Component
• Main Bearing Set (J2/J3)
• Cross-Roller Output Bearing
• Primary and Secondary Seal Kit
• High-Torque Fastener Set (Grade 12.9)

Tools

• Torque wrench with appropriate range for Grade 12.9 fasteners
• Metric hex key and socket set
• Bearing puller set
• Seal installation tool or appropriately sized drifts
• Soft mallet
• Grease gun with NexBot-specified bearing and gear grease
• Lint-free cloths
• Non-residue solvent cleaner
• Mechanical support stands or crane for robot arm sections

Procedure

This procedure covers the J2 axis. The process for the J3 axis is mechanically analogous, though access and fixturing will differ. Refer to the specific robot service manual for details on supporting the J3 link arm.

Step 1: Preparation

1. Jog the robot to its zero or a designated maintenance position that provides safe access to the J2 and J3 axes.
2. Perform the full LOTO procedure on the robot controller.
3. Secure the robot arm (J3 and onwards) using an overhead crane or certified mechanical support stands to prevent it from falling once the J2 joint is disassembled.
4. Carefully disconnect the motor power and encoder cables for the J2 and J3 motors. Label them clearly to ensure correct re-connection.

Step 2: J2 Axis Disassembly

1. Remove the outer covers to access the J2 axis motor and reducer assembly.
2. Unbolt and remove the J2 axis motor. Set it aside in a clean, safe location.
3. Following the service manual instructions, carefully remove the bolts securing the harmonic gear reducer's output flange.
4. Extract the old Wave Generator assembly from the motor shaft spline.
5. Remove the old Flexspline component. This may be a tight fit and require care to avoid damaging surrounding surfaces.
6. Using a bearing puller, remove the Cross-Roller Output Bearing from the robot base or link.
7. Carefully pry out the old primary and secondary seals. Avoid scratching the seal bores.
8. Thoroughly clean all mating surfaces, bearing seats, and seal bores with a non-residue solvent and lint-free cloths. Inspect for any damage, burrs, or wear.

Step 3: J2 Axis Assembly

1. Using a seal installation tool, carefully press the new seals from the kit into their respective bores until they are fully and squarely seated.
2. Lightly lubricate the new Cross-Roller Output Bearing with the specified grease. Install the bearing, ensuring it is correctly oriented.
3. Install the new Grade 12.9 fasteners. Tighten them in a star or crisscross pattern in three stages (e.g., 30%, 60%, 100%) to the final torque value specified in the robot's service manual. Using a calibrated torque wrench is mandatory.
4. Install the new Flexspline component, ensuring it is properly aligned.
5. Install the new Wave Generator assembly onto the motor shaft.
6. Re-install the J2 motor, using the new fasteners provided in the kit. Torque these fasteners to the value specified in the service manual.

Step 4: Repeat for J3 Axis

1. With the arm still safely supported, repeat the Disassembly and Assembly steps for the J3 axis components.
2. The procedure is similar, but requires careful management of the J3 arm link during the process.

Verification

1. Reconnect all motor and encoder cables for J2 and J3.
2. Re-install all robot covers.
3. Remove all tools, supports, and personnel from the robot work envelope.
4. Carefully remove the LOTO and power on the robot controller.
5. Perform a robot mastering/calibration procedure for the J2 and J3 axes. This step is critical to re-establish the robot's positional accuracy.
6. In teach pendant mode, jog the J2 and J3 axes slowly through their full range of motion. Listen for any unusual noises and watch for any binding or jerky movement.
7. Run a test program at low speed (25% or less) to confirm smooth operation.
8. Reset the 8,000-hour maintenance timer for the J2/J3 axes in the controller software.
9. Document the maintenance in the robot's service log.

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