Strange behaviour - sudden axis reverse

[kucharzb]

Hi,

I am not sure whether it is software or hardware problem - here a description:

rarely, happens in around 3-5% of machine turn on procedure (and it also happened few times in normal operation with manual movement using controller). My CNC is equipped with UC300ETH-5LPT and ihss60-36-30-21-38 jmc CL Steppers. Maschine starts in "reset" mode, after I unreset it I usually do "homing" procedure. Sometimes instead of doing standard Z Axis slow movement up (250mm/min), maschine makes rapid movement in other Z direction (down), and after short distance, the stepper is going into Error (probably, due to excess speed/accelleration). It makes sound as if it was trying to make G0, Z-axis down. This usually happens in homing, but also sometimes it does this error on diferent axis while manual jogging. Can anybody help me narrow down the issue? I might try to record the video, but since it happens not often it is hard to film it.

thanks,
Kris

[cncdrive]

I would check the Act feedrate DRO first when the issue happens to see if the UCCNC really sending that high feedrate.
Also I would measure the step frequency when the issue happens.

I think the UCCNC is not likely doing this kind of error or at least I don't remember anybody reported such problem.

Maybe the issue is that the closed loop stepper drive is loosing the encoder signal, it could cause a runaway of the motor with high feedrate.