X and Y stepper stalling, Cartesian machine

  • Hi all,

    Looking for some help with a strange error that has recently popped up. For certain gcode files that I've recently ran, the starting skirt is a large circular shape. At the top of the circle (say around X800 Y80 plus or minus a few, with bed center being X0Y0, bed size 200x200) the X axis stepper and possibly the Y axis stall/stutter and lose steps. This doesn't happen at any other point of the larger circle, and smaller circles seem unaffected.

    At first I thought this was a firmware/software issue but now I suspect it may be mechanical in nature. Does anyone have any thoughts or suggestions I that might work, like bumping up the amperage supplied to the steppers from 855 to 900 or something like that? (using a 24v PSU, Duet Web Control reading VIN at 24.4V)

  • Moderator

    Your motor currents should be 70-85% of their rated max ideally.

    If you disconnect the belts can you slide the mechanism smoothly by hand?

  • Yes, there are no hangups on the smooth rods whatsoever.

  • Moderator

    And your motor currents?

  • @phaedrux From the documentation on the stepper motors I have, their max rated current is 1.2A, and I have them running at 955mA, should I try to bump that up to between 960mA - 1.02A?

  • Moderator

    You can try bumping the current temporarily to see if it makes a difference. No harm there. The motors will get a bit warmer.

    But if the extra current does help that would indicate maybe some mechanical binding somewhere that the extra current is helping to overcome. Ideally the source of friction would be eliminated.

    Is there anything else particular to that point of motion? Does a wiring harness get flexed there possibly causing an intermittent break in a wire? Does something contact the bed? Is something askew or misaligned?

  • Nothing should be contacting the bed, using 16 point mesh bed compensation and the height map is very flat. The only wires that could possibly be binding would be the wire harness coming from the extruder and the bed heating/thermistor wires (unlikely but possible), not sure if that would have an effect on the X or Y axis steppers. I'll take another look at the mechanics and the wiring to see if anything is hanging up after I try and bump up the motor currents a bit.

    Thanks for the suggestions, I appreciate the help!

  • Moderator

    Can you post the gcode that has the problem? It's possible that the skirt has some odd extrusion patterns. What are you slicing with? Can you also post your config.g? Also can you post the results of an m122 from after the problem has occurred?

  • Sliced with Cura 3.6; gcode is over the allotted file size limit, would you like me to edit it to only include the first half of the file? Will post config.g and M122 once I am able to start the print up again. Would it help to have one sent during before and after the problem occurs?

  • Moderator

    @red-sand-robot sure as long as the portion with the skirt is included that's enough to see. M122 before and after. Only post the before if you see a difference.

    If you zoom in on the Cura preview of the offending section does it look strange in anyway?

    If possible could you export a .3MF file from Cura and post it on Dropbox or something? That would include everything of relevance.

  • Well, turned out the issue was mechanical after all. My part cooling fan was running into a zip-tie around the strain relief I have for my bed heater cables. I feel kinda dumb for missing that.

    Sorry for wasting your time, and thanks again for attempting to help!

  • Moderator

    @red-sand-robot hey no problem. Glad you got it sorted out.

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