Scheduled Maintenance for R-50/R-100 J2/J3 Axis Using the 762-001 Joint Overhaul Kit

Related Products

Tools Required

• Torque wrench (calibrated)
• Metric socket and wrench set
• Metric hex key set
• Bearing puller kit
• Bearing/seal press or driver set
• Grease gun with harmonic drive grease
• Certified robot arm support/lifting equipment
• Lockout/Tagout (LOTO) kit

Article

This document outlines the standard procedure for performing preventative maintenance on the J2 (waist) and J3 (shoulder) axes of NexBot R-50 and R-100 series articulated robots. The use of the NXB-KIT-762-001 Joint Overhaul Kit is required to complete this task. This maintenance addresses wear-related issues such as increased backlash, audible noise from the joint, or minor positioning inaccuracies, restoring the robot to its original performance specifications.

Schedule

This is a major preventative maintenance task recommended at an interval of 8,000 operational hours or if diagnostic systems indicate excessive backlash or positioning errors in the J2 or J3 axis. Performing this overhaul on schedule is critical for preventing unplanned downtime and ensuring consistent production quality.

Parts Needed

All necessary replacement components are included in the NexBot Robotics 762-001 Joint Overhaul Kit. Verify the kit is sealed and contains all of the following before beginning the procedure:

• Kit SKU: NXB-KIT-762-001
• Kit Contents:
• 1x Wave Generator Assembly
• 1x Flexspline Component
• 1x Main Bearing Set (for J2/J3 axis)
• 1x Cross-Roller Output Bearing
• 1x Primary and Secondary Seal Kit
• 1x High-Torque Fastener Set (Grade 12.9)

Procedure

WARNING: This procedure must be performed by a certified technician. Failure to follow safety protocols can result in severe injury or death, and damage to the equipment. Always consult the official NexBot service manual for your specific robot model before proceeding.

Step 1: Safety and Preparation

1. Move the robot to a maintenance position where the J2 and J3 axes are accessible and not under heavy load. If necessary, use an overhead crane or certified lifting equipment to support the robot arm.
2. Perform a full Lockout/Tagout (LOTO) procedure on the main electrical disconnect for the robot controller.
3. Verify that all stored energy (electrical, pneumatic, hydraulic) has been dissipated.
4. Disconnect the main power and control cables from the base of the robot.

Step 2: Disassembly

1. Remove the outer cosmetic and protective covers for the target axis (J2 or J3). This typically involves removing several M6 hex bolts.
2. Carefully disconnect the axis motor power and encoder cables. Label the cables to ensure correct reassembly.
3. Unbolt the axis motor from the robot casting. Store the motor in a clean, safe location.
4. Before removing the harmonic drive assembly, mark the orientation of the existing components relative to the robot casting.
5. Following a star pattern, incrementally loosen and remove the main fasteners securing the harmonic drive assembly and output flange. The included fastener set in the kit is for replacement.
6. Carefully remove the old harmonic drive (Wave Generator and Flexspline), followed by the Cross-Roller Output Bearing. A bearing puller may be required.
7. Remove the old primary and secondary seals from the casting. Take care not to scratch or damage the seal seating surfaces.

Step 3: Cleaning and Inspection

1. Thoroughly clean all mounting surfaces inside the robot joint casting. Remove all old grease, debris, and sealant.
2. Inspect the machined surfaces for any signs of damage, scoring, or corrosion. Report any significant damage to NexBot Robotics support.
3. Ensure the new components from the NXB-KIT-762-001 are clean and free from any packaging debris.

Step 4: Installation

1. Using a seal driver or appropriate press tool, carefully install the new Primary and Secondary Seals from the kit into the casting. Ensure they are seated evenly and at the correct depth.
2. Install the new Cross-Roller Output Bearing. This is a precision component; ensure it is pressed in evenly and without canting. The bearing should be a light press fit.
3. Install the new Main Bearing Set according to the orientation specified in the service manual.
4. Apply the recommended harmonic drive grease to the new Flexspline component.
5. Install the new Flexspline and Wave Generator Assembly, aligning them with the marks made during disassembly.
6. Loosely install the new Grade 12.9 fasteners from the kit. Following the torque sequence in the service manual, tighten the fasteners in a star pattern to the specified torque value (e.g., an M8 Grade 12.9 fastener may require 34 Nm, but always refer to the manual for your specific robot).
7. Re-install the axis motor, ensuring proper engagement with the Wave Generator spline. Torque the motor mounting bolts to specification.
8. Reconnect the motor power and encoder cables.
9. Re-install all axis covers.

Verification

1. Remove all tools from the work area and complete the end-of-work LOTO procedure to re-energize the robot controller.
2. Power on the robot. Check the teach pendant for any alarms or errors related to the serviced axis.
3. In manual mode and at a very low speed (10% or less), jog the J2 and J3 axes through their full range of motion. Listen for any unusual noises and watch for any binding or jerky movement.
4. Perform the robot's mastering or calibration procedure for the serviced axis. This is critical to re-establish the robot's zero position and ensure accuracy.
5. Run a test program that moves the arm through various positions to confirm that positioning is accurate and repeatable. Monitor the axis load and positioning error values on the teach pendant to ensure they are within specification.
6. After a brief operational test, check the joint for any signs of grease leakage, indicating a potential seal issue.

Keywords