A4988 suddenly lost it's holding torque

Hi, there!

I deceloped 1-axis linear guide with a4988,
I had run it for 5-6 hours, than it start not to work in a weong way.

it does not stop where it stopped. It moves a little more. It seems like nothing hold the motor. When I turn the motor by fingers, it moves around 90-180 degrees. The motor was a little hot, but not so high. 40-50 celscious maybe.

Do you have any idea for this?


Are you saying the stepper seems to move correctly when driven but that when the motion stops, there is no holding torque? Can you post pictures here that show how you have everything connected?

Did you set the current limit on the stepper driver and, if so, how did you set it and what did you set it to? What kind of power source are you using for the motor and what is its voltage? What are the voltage and current ratings for your stepper motor?

Did something change before it stopped working? Did the failure occur on a power cycle (turning the power off and then on again)? Does your circuit have an electrolytic capacitor between VMOT and GND near the board?