I. Preparation
Safety protection: Cut off the power supply of the equipment and lock it. Wear dust-free gloves and finger cots.
Environmental preparation: Perform in a clean bench or clean room. Thoroughly clean the work area.
2.Tools and consumables:
Original special nut removal tools (such as removal pins, clamp wrenches, etc.).
A complete set of new balls of the same batch and specifications from the original factory.
High-purity, designated brand special grease for ball screws.
Precision instrument cleaning agent (no residue, non-corrosive).
Dust-free wipes, dust-free finger cots.
Precision tweezers.
Magnifying glass or microscope.
Torque wrench (for re-tightening the nut housing).
Vaseline or high-viscosity grease (for temporary fixing of the ball, optional).
Disassemble the screw assembly: Carefully remove the screw nut assembly from the device according to the specifications (absolutely avoid screwing the nut out of the end of the screw!). Clean the outside thoroughly.
-Core steps: disassemble the nut & replace the ball
I. Nut disassembly (Critical!):
Locate the disassembly point: Find the disassembly hole (usually blocked by a screw) or the special clamp structure on the nut housing. You must refer to the official maintenance manual of the nut model.
Use special tools: Insert the disassembly hole with a special disassembly pin, or loosen the clamp with a clamp wrench. Violent knocking or prying is strictly prohibited!
Carefully separate the housing: Usually the nut will be split into two halves along the axial direction or open the end cover. Move slowly and pay attention to the position and direction of the internal components (returner, bead block, seal). It is strongly recommended to record the whole process by video or photo recording.
Expose the ball circulation system: At this time, you can see the arrangement of the balls in the raceway and returner.
II. Remove the old balls and clean them:
Record the number and arrangement of balls: Count the total number of balls carefully and observe how they are arranged in the circulation channel (is it a full ball design or is there isolation? What is the return path?).
Remove the balls carefully: Use dust-free tweezers or a bead suction tool (if available) to remove all old balls and put them in a clean container in order. Avoid the balls from colliding with each other or falling off.
Thorough cleaning: Clean all nut parts (housing, internal raceway, returner, bead block, sealing groove) repeatedly with precision cleaning agent, wipe with a dust-free cloth, and blow dry with filtered and dry compressed air. Make sure there is absolutely no residual grease, metal debris and dust. Check all parts for damage (scratches, deformation, cracks).
III. Install new balls (the most difficult!):
Lubrication preparation: Apply a thin and even layer of special grease on all raceway surfaces and the inner wall of the returner channel. This helps the balls to be in place and temporarily fixed.
V. Use tools to help (critical!):
Guide tube/needle: Some designs can use a small guide tube to insert into the return inlet and carefully feed the balls one by one into the raceway.
Cage/spacer: If the original design has a cage, the cage must be accurately reset to the correct position first.
Temporary sticky medium: A small amount of petroleum jelly or high-viscosity grease can be applied to the tip of the tweezers or the ball to help pick up and place the ball (remove excess residue with a cleaning agent after completion).
VI. Accurately place the balls:
Use precision tweezers to carefully place the new balls one by one at the starting position of the raceway according to the number and original arrangement order recorded during disassembly.
Be extremely gentle to avoid scratching the raceway or impacting the balls.
Make sure each ball falls correctly into the raceway groove.
Complete the circulation channel filling: Carefully pass the balls through the return or end cap channel to gradually fill the entire circulation loop. This process requires great patience and feel to ensure that no balls are stuck in the return path and all balls can roll smoothly. This is the most likely step to fail!
VII. Reassemble the nut:
Make sure that the internal components such as the returner, bead plate, seal, etc. are accurately reset to the original position and direction.
Apply a small amount of grease to the lip of the seal.
Carefully align the two halves of the nut housing or end cover and close them accurately.
Use special tools and torque wrenches to tighten the housing connection screws or clamps in the order and torque value specified by the manufacturer. Uneven or excessive tightening force will cause the housing to deform and jam the balls!
-Subsequent steps (still critical)
Manual test: Carefully screw the repaired nut into the screw (still within the effective stroke!). Rotate the nut very slowly forward and reverse, and feel whether the resistance is uniform, whether there is any stuck point or abnormal friction throughout the process. If there is any difficulty, stop immediately and disassemble and check.
Preliminary lubrication: Add an appropriate amount of special grease through the grease nozzle.
Assembly installation and calibration: Install the screw nut assembly back into the device with extreme care. Strictly ensure:
High-precision coaxiality of the bearing seats at both ends (calibrated using a dial indicator/laser).
No stress distortion in the nut mounting seat.
Precision alignment of the coupling and the motor.
Preload adjustment: For adjustable preload nuts, the preload must be reset to the manufacturer’s exact value using professional tools (torque wrench, preload gauge). It cannot be adjusted by feel!
–Full test:
Run at low speed and no load, listen for noise.
Measure axial clearance (dial indicator).
Test temperature rise at different speeds.
Perform positioning accuracy and repeatability detection. Even if the replacement is successful, the accuracy will usually be one level lower than the original new part