Stepper motor lost torque



  • Bit of an odd one and gonna swap the stepper over to a new one to rule that out to check but my extruder stepper has lost torque, sits clicking away and even with minimal load such as loading fillement down the Bowden tube it's skips a bit, I had to rush out but I just wanted to check if there's anything I can check on the duet side to see if this is a board issue? I guess I could up the current as have it on the low side to keep cool as possible in my heated chamber (27c at the time as printing petg)

    Duet WiFi if that makes any difference? I push the stepper fairly hard with a 1mm volcano nozzle and a heated chamber (never over 45c) but haven't had a stepper suddenly loose power on me before.


  • administrators

    Check the crimp connections in the wiring. Also check that you haven't inadvertently reduced the motor current.

    This type of problem can also be caused by a partially blown stepper driver. So it the problem persists after you have checked the current and checked and/or remade the cimp connections, try using a different motor output.



  • I hadn't thought to look at the wiring but thinking about it I had a print fail a week back that ended up nudging the wiring under the stepper. Blown driver was my biggest fear as all are currently used for extruders, 900ma with active cooling (no heatsinks) should be well within the limits though? I got donated the board by a mate who had given up with his printer so don't know it's history so can't guarantee it hasn't been abused.


  • administrators

    The Duet WiFi/Ethernet doesn't normally need any cooling unless you run the motors at 2A or higher.



  • I Know and chips stayed cool enough to touch during a long print, I just went with better safe than sorry approach as the duet is in the heated build chamber. I plan on moving outside when I get a chance but that'll involve lengthening all the wires so been putting it off.



  • So this is turning out to be interesting....

    -swapped stepper, still got the issue
    -new wiring, still got the issue
    -swapped to e1, still go the issue

    No idea where to go from here! ☹



  • @oliverracing If the motor sits there clicking away but nothing else happens and it isn't the motor, or the wiring, or the motor driver then it must be something wrong with the extruder itself. What extruder is it?



  • @deckingman That was my thought - I checked it out of the extruder too but it can barely turn the extruder drive gear when held in my hand (direct on the output shaft). I've tried upping the current to 1500ma and that changes the clicking to a louder clicking but still struggles to turn the drive gear in my hand



  • if the motor driver is active its hard to turn the motor shaft, if the driver is not active it should spin relatively freely if not mechanically loaded somehow.



  • @bearer yeah I know, when active it feels a little stiff (I know this normally feels a lot harder to turn than this) and almost rough but completely smooth when off for both. Tearing my hair out at the moment as no idea what's going on.



  • So if you disconnect the motor is it the same? If you disconnect and short out the coils is it the same? Sounds like something is shorted, and those two should help point towards bad wiring or bad drivers.



  • @bearer nope, when disconnected the motor spins freely but when powered it's got such low holding torque I can turn the Shaft by hand with much lower amount of force to normal


  • administrators

    @oliverracing said in Stepper motor lost torque:

    @bearer nope, when disconnected the motor spins freely but when powered it's got such low holding torque I can turn the Shaft by hand with much lower amount of force to normal

    What current are you running the motor at? Can you provide a link to the data sheet?

    Send M906 without parameters to check that the current is what you think it is. Also M913 to check that it is at 100%.



  • I'm running the motor at 900ma - and have been for ~2 years, Tried M906 to set the current up to 1500ma just to check if that made any difference (definitely added torque, just not much). I'll try M906 and M913 to check tonight - at work at the moment so hold fire on this.

    As for specs of motor - they are the basic ones that originally came on the Tevo Tarantula that my printer once was based on. I have also tried a similar spec motor fresh from the box and this shows the same issue making me think it's unlikely to be a motor issue. I've made a fresh wire, so making that unlikely and tested the new and old (in that order) on the E1 driver and that had the same issue.

    Can't work out how to link so here are the specs...
    Drive Shaft - - - - - - - - - - - - - - - - - - - - - - - - - - - - 4.5mm
    Step Angle - - - - - - - - - - - - - - - - - - - - - - - - - - - - 1.8°
    Step Angle Accuracy - - - - - - - - - - - - - - - - - - - - 1.8 ° ± 5%
    Holding torque - - - - - - - - - - - - - - - - - - - - - - - - 420mN.m(I=1.5A)
    Rated Current/Phase - - - - - - - - - - - - - - - - - - - 1.5A
    Phase Resistance - - - - - - - - - - - - - - - - - - - - - - 1.6±10%
    Voltage - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 2.4V
    Inductance - - - - - - - - - - - - - - - - - - - - - - - - - - - 3.8mH±20%
    Positioning Torque - - - - - - - - - - - - - - - - - - - - - 18mN.m REF.
    Maximum load starting frequency - - - - - - - - - 1400pps
    Maximum no-load operating frequency - - - - - 8000pps
    Moment of inertia - - - - - - - - - - - - - - - - - - - - - - 57gcm
    Ambient temperature - - - - - - - - - - - - - - - - - - _ -20 ~ 50



  • @oliverracing said in Stepper motor lost torque:

    @bearer nope, when disconnected the motor spins freely but when powered it's got such low holding torque I can turn the Shaft by hand with much lower amount of force to normal

    To recap, this was working fine but the fault suddenly started without you making any changes to the configuration files.

    What you are describing (i.e. you can easily turn the motor by hand, even when the holding current is set to 1500mA) indicates that only one pair of coils is being energised. I can only think of three possible reasons for that. 1) The motor itself is faulty but you say you've tried another. 2) There wiring is faulty but you say you've replaced it all. 3)The driver is faulty but you say you've tried another driver.

    One thing occurs to me but I don't know if it is possible, is that the stepper developed a fault which took out the driver chip. You then tried that motor on another driver but because of the fault, it instantly took out that driver chip too. @dc42 will know if that's possible.

    If not, then it only leaves highly improbably scenarios. 1) The stepper you replaced it with is also faulty. 2) The wiring you replaced is also faulty. 3) The driver you swapped with is also faulty.

    It's easy enough to test a stepper motor to see if both coils are healthy - just do an internet search which will reveal a number of methods depending on what tools you have available. Once you have established that you have healthy stepper motor, connect it to a known healthy driver - such as one of the axis drivers. If it doesn't work, then it has to be the wiring between the stepper and the driver. If it does work, then it has to be a faulty driver (or two).



  • @deckingman Spot on and and thank you for putting it far more elegantly than I ever could! I'll go though in that order to try and work out what's going on.



  • Damn

    That didn't end well (the short to ground warnings). Pop and burning smell with this warning in DWC. Had previously checked M906 - came back with E900:900 and M913 with returned 100%. Unplugged and replugged all connectors to do with extruder to check and tried a 1mm extrude and pop.

    For reference the e0 driver now has a little hole in it



  • Just looking for a replacement chip, is it a TMC2660-PA-T or TMC2660-PA that I need to be a direct swap and is it just a case of removing the old chip and soldering the new one on?



  • before you do any chip replacement you need to go on a hunt for what was causing the problem.

    start by checking the resistance of each phase of the stepper that you had connected.


  • administrators

    @oliverracing said in Stepper motor lost torque:

    Just looking for a replacement chip, is it a TMC2660-PA-T or TMC2660-PA that I need to be a direct swap and is it just a case of removing the old chip and soldering the new one on?

    Yes that's the one. I think the -T suffix just means that it is supplied on a reel. But before you replace it, how old is your Duet? If the driver failure wasn't your fault, replacement is covered by the warranty.


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