When a stepper motor gets hot, it loses steps and fails to rotate. Under no-load conditions, the following may be the reasons:

• Excessive load or stuck: If the motor load is too large or the motor bearings are stuck, it will cause the motor controller to continuously output current, causing the motor to overheat, and it will easily lead to loss of steps and the motor not rotating.
• Drive circuit problems: Unreasonable drive circuit design or unstable drive voltage will cause the motor to heat up and affect its normal operation.
• Poor heat dissipation of the motor shell: When working in a high temperature environment for a long time, poor heat dissipation of the motor will cause the motor temperature to be too high and easily damage the motor.
• The stepper motor generates serious heat: The stepper motor itself generates a certain amount of heat due to its working principle. However, if the motor heats up severely, there may be a problem with the motor's internal windings or iron core, which requires inspection and repair.

To solve this problem, the following measures can be taken:

• Check the load: Make sure the motor load is within the normal range to avoid overload or underload. At the same time, check whether the motor bearings are normal. If any abnormalities are found, they need to be replaced in time.
• Check the drive circuit: Make sure the drive circuit design is reasonable and the drive voltage is stable. If there is a problem with the drive circuit, it needs to be repaired or replaced in time.
• Optimize heat dissipation: Ensure that the motor casing has good heat dissipation conditions. You can install heat sinks or fans and other heat dissipation equipment on the motor casing to help the motor dissipate heat quickly.
• Check the motor: If the motor heats up severely or other abnormalities occur, the motor needs to be inspected, repaired or replaced in time.