Why Does the Shaft of a Stepper Motor Move Back and Forth (Axial Play)?

Generally, a small amount of axial play in a stepper motor shaft is normal. Most stepper motors are designed with axial clearance, and a wave spring washer is often installed behind the rear bearing to absorb cumulative tolerances. However, sometimes the play can be caused by a mechanical fault. Here are some troubleshooting methods:

1. Power-off Manual Check: Disconnect the motor from any load (remove the timing belt/coupling). Rotate the motor shaft by hand while gently pushing and pulling the shaft axially. Pay attention to:

• Does it rotate smoothly? If you feel any roughness or binding, the bearings might be damaged.
• How much axial clearance is there? If the clearance is small (<0.3mm) and feels springy, it's likely the normal wave spring washer. If the clearance is large and feels loose, it indicates a problem with the internal bearings or positioning components.

2. No-load Running Test: Run the motor completely unloaded (not connected to anything). Power it on and run it at different speeds. Observe if the axial play persists.

• If the play disappears under no load: The problem is 100% with the external mechanical installation and connection.
• If the play persists under no load: The problem lies within the motor itself (e.g., bearing issue or structural defect).

3. Check Operating Conditions: In applications involving pressing or similar axial loads, the motor's rear may require support, such as shims. Otherwise, the wave spring washer can be over-compressed, permanently losing its elasticity. This will increase the axial clearance, leading to noise during high-speed operation.

Conclusion: The motor contains a wave spring washer. Applying significant axial force to the shaft will inevitably reduce the spring washer's elasticity, making any inherent play more noticeable. If the axial force permanently damages the elasticity of the wave spring washer, the motor will exhibit increased axial play. Therefore, every stepper motor has a specified axial load capacity that must not be exceeded.

Regarding axial clearance, it is a standard feature in most stepper motors, with the wave washer in the rear bearing serving to accommodate manufacturing tolerances. If the application cannot tolerate any axial play, a solution incorporating a locking mechanism should be selected.

Updated on: 26/09/2025