Single Y Axis stepper hitching/clunking?

Hello all!

I’ve been fighting with a really strange issue with my 1000mm X-Carve.

For the last 2 months, its refused to cut perfect circles, instead giving me a ‘flat tire’ at two points during the cut. I have spent about 8 hours troubleshooting it, running through many of the suggestions here and scouring Youtube for a resolution. A quick summary: I’ve adjusted belt tension, v wheels, triple checked wiring, adjusted pots, steps/mm, used various software toolchains, nothing seems to fix it.


I performed a very slow aircut of a circle yesterday which I think has revealed the source of the problem, but I don’t know what to do about it. At normal speeds, there don’t appear to be any physical manifestations (Other than the horrible cut) of the problem, but at low speeds, there is a visible stop in the left Y stepper and an audible “clunk”. It only happens when the stepper changes directions.

I’ve uploaded a Youtube video demonstrating it. I first show the right side working correctly, then the left, failing.

Link to video on Youtube.

My assumption is that my stepper may be dying, does that seem reasonable? Since then I have noticed that on large jobs, my Y axis seems to be consistently off by approximately 5% regardless of what the dimensions are. I can seemingly dial in the steps/mm just right, but it seems to drift again after the first cut.


Check the set screws in the pulley for the motor that is “clunking” when you change direction.

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Larry, does that look like a hitch in the x axis and not y? Also, your belts are running up against the edge of your pullies and idlers. Could lead to premature belt wear.

I did not, I will investigate and post back as soon as I’ve given those suggestions a shot! I will need to wait until later tonight, it is Father’s day of course :smile:

Thanks everyone for their advice, I really appreciate it!

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