Maintaining Joint Precision Using the NXB-GEN-833-013 Washer and Spacer Set

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Tools Required

• Calibrated torque wrench
• Metric hex key set
• Digital calipers or micrometer
• Feeler gauges
• Lint-free cloths
• Appropriate PPE (Safety glasses, gloves)
• Lockout/Tagout (LOTO) kit

Article

This document outlines the standard maintenance procedure for inspecting and replacing shims, washers, and spacers in critical NexBot robotic arm joints using the NexBot Robotics 833-013 Washer And Spacer Set (Stainless Steel). Proper joint spacing is essential for positional accuracy, repeatability, and the long-term mechanical health of the robot. This procedure should be performed by qualified technicians when addressing issues of joint backlash, positioning errors, or as part of a major service interval.

Maintenance Schedule

This maintenance is not typically part of a routine daily or weekly check. It should be performed under the following conditions:

• During scheduled major service intervals (e.g., annual or multi-thousand-hour service), as specified in the robot's primary service manual.
• When troubleshooting and diagnosing excessive mechanical backlash or 'slop' in the J2, J3, or J6 axes.
• After a joint motor or gearbox replacement where component stack-up may have been affected.
• If positioning repeatability tests show a degradation in performance isolated to a specific joint.

Parts Needed

• NXB-GEN-833-013: NexBot Robotics 833-013 Washer And Spacer Set (Stainless Steel). This set contains a calibrated assortment of high-precision washers and spacers required for the procedure.
• Appropriate thread-locking compound (refer to robot service manual for specification).
• Approved cleaning solvent (e.g., Isopropyl Alcohol).

Safety Precautions

WARNING: Failure to de-energize the robot can result in serious injury or death. Always follow established safety protocols for your facility.

1. Power Down: Completely power down the robot and its controller.
2. Lockout/Tagout (LOTO): Apply LOTO devices to the main electrical disconnect for the robot cell in accordance with safety regulations.
3. De-energize: Verify that all electrical, pneumatic, and hydraulic energy sources are at a zero-energy state.
4. Secure Manipulator: If necessary, use certified overhead lifting equipment or mechanical braces to support the robot arm to prevent unexpected movement or collapse when joint components are removed.
5. Personal Protective Equipment (PPE): Wear appropriate PPE, including safety glasses and protective gloves.

Procedure

This procedure provides a general workflow applicable to compatible joints (J2, J3, J6) across various NexBot series like the R-20, R-50, C-10, and S-5. Always consult the specific service manual for your robot model for detailed diagrams and torque specifications.

Step 1: Access the Joint

• Move the robot to a designated maintenance position that provides safe and clear access to the target joint.
• Carefully remove any plastic covers, cable management brackets, or external components obstructing access to the joint's mechanical housing and fasteners.

Step 2: Initial Inspection

• With the joint covers removed, visually inspect the area for signs of excessive wear, metal shavings, or lubricant leakage, which may indicate a more severe issue.
• Manually attempt to move the robot link connected to the joint. Note any perceptible 'clunk' or backlash. This will serve as a baseline for post-service verification.

Step 3: Component Disassembly

• Identify the primary fasteners for the component that requires shimming (e.g., the gearbox output flange or bearing housing).
• Carefully loosen and remove the fasteners in a star or crisscross pattern to ensure even pressure release.
• Gently separate the components. Be prepared for existing shims or washers to be present. It is critical to collect and measure these original parts.
• Note the exact order and orientation of all removed components, including the original spacers.

Step 4: Cleaning and Measurement

• Thoroughly clean the mating surfaces of the disassembled components, as well as the original washers, using a lint-free cloth and an approved solvent.
• Using a calibrated digital caliper or micrometer, measure the thickness of the original washer/spacer stack.
• Refer to the robot's service manual for the required clearance or preload specification for that specific joint. This value is critical.
• Compare the required specification with your measurements to determine how much shim thickness needs to be added or removed.

Step 5: Select and Install New Hardware

• From the NXB-GEN-833-013 set, select the combination of washers and spacers that achieves the precise thickness required to meet the specification. The high-grade 304 Stainless Steel construction ensures dimensional stability and corrosion resistance.
• Place the new washer/spacer stack onto the designated surface, ensuring they are flat and correctly seated.

Step 6: Reassembly and Torquing

• Carefully reassemble the joint components, ensuring proper alignment.
• Apply the specified thread-locking compound to the fastener threads if required by the service manual.
• Install the fasteners finger-tight, then use a calibrated torque wrench to tighten them to the manufacturer's specified torque value in the recommended sequence (typically a star pattern).

Verification

1. Mechanical Check: Manually articulate the joint to ensure it moves smoothly without binding or excessive resistance.
2. Power Up: Remove LOTO devices and power the robot system back on, following standard startup procedures.
3. Jogging: In a slow manual mode (T1), jog the affected joint through its full range of motion. Listen for any abnormal noises and watch for any motor strain or controller errors.
4. Repeatability Test: If available, run the robot's position repeatability or calibration routine to confirm that the joint's accuracy is now within acceptable limits.
5. Final Inspection: Reinstall all covers and components removed during the procedure. Run a test program to validate the repair under normal operating conditions.

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