Extruder motor skipping steps and loud clicking


This is my first time to use Repetier Firmware.

When testing the extruder motor without hot end and cold end, it starts smooth with the first couple of tests and then starts skipping steps in a pattern. The motor current rating is 1.68A, started with 70% of max Vref and readjusted it to max Vref 0.67V. it was attached to hot & cold end but the problem exists in all conditions. I feel like it is a firmware setting that I need to adjust but I am lost. The board is RUMBA and driver is A4988

Please lead me to the probable reason and how to solve it.

I couldn’t uploade a video here, so it is on youtube


  • Do you already have stepper driver coolers and fan blowing on it? To me it looks like motor is loosing current from time to time. So if that was just one move it could be overheating of the drivers and then they disable power for a period and continue. Other thing is if were several moves you have maybe set timeout to disable all motors to a second an dtherefore it goes back to unpowered position before starting again.
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