Stepper Motor Connector scroched/overheated

  • Hi,

    While cutting today, my x-axis went haywire, and the associated motor was behaving erratically subsequently, in particular for short steps. Also noted messages 'Warning : Phase B.....maybe disconnected.

    When I reviewed the wiring I noticed the associated pin's on the Duet looked like this,


    Y and Z are fine, X is the only one in this state.

    I am hoping this is a motor failure, any insights ?

    Thanks for your help,

  • given that the latch is bend backwards, did you recrimpt the wire and use the connectors that came with the duet?

  • Hi,

    It was part of a Workbee kit, wiring came pre-configured, has been working fine for six months.

    The connector was stiff to remove, hence latch being pushed back during the process. Looks like some of the plastic connector may have melted, externally 'brown' shadow where connectors are.


  • @rn-obrien said in Stepper Motor Connector scroched/overheated:

    has been working fine for six months.

    apparently not. its a good idea to recrimpt the connectors. especially if you are running high current.

  • @rn-obrien from what you've said, my guess is that one or two of the crimps in the connector have had a poor connection and heated up under load. Could also be that the connector wasn't seated properly if the retainer latch is bent back like that.

    If you're lucky, it will have just melted the plastic housing of the connector and won't have done anything too damaging to the board. Clean up the pins as best you can and redo the connector. You will need new crimps and possibly a new plastic body for the connector if that's damaged (not sure if you get spares with the Workbee kit?). Double and triple check you get the motor phases wired up correctly when you put it back together.
    At the same time I'd also check all of your other connectors in case they've got dodgy connections.

    A few thoughts that might help prevent issues in the future... don't try unplugging connectors by pulling on the wires. You can get hold of them with a pair of long nosed pliers on the connector itself and they'll come out easily with a little wiggle. That way you'll avoid straining the wires and crimps which could lead to damage. Also, the latches are there to help make sure the connector is seated properly and make good electrical connections (and stay that way even if the machine vibrates a lot!). I really would not want to break them off/bend them back like that!

    Edit: just realised you bent the latch after the issue occurred to get the damaged connector off...

  • Guys,

    Thanks for feedback, much appreciated. Will organise a new connector, and see how I get on.


  • administrators

    Also check the soldering of those connector pins on the underside of the Duet. Most likely the overheating was caused by bad crimp connections, but bad solder joints are not impossible.

  • Check the Duet board to look at the traces from the scorched pins. Also pay particular attention to the solder joints on the pins. If they look odd or just 'different' from those of unburned connectors, there is a good chance the joint is damaged. It may measure ok but chances are it will be prone to heating up.
    If that is the case, you need to remove the old connector/pins, remove the excess solder and install a new connector with fresh solder.

  • We use NEMA 24 motors for Y and Z axes with current set to 1.5 A and overheating pins are very common. Connectors are hot and often burn to dark brown colour around pins.
    Yesterday one of the printers started to behave strangely and the problem appeared to be completely burned and detached wire, just before the crimp.
    The crimps has to be high quality and strongly pushed to the pin, but to be honest many of the burnt ones I would never suspect are bad.
    Just a moment ago Y axis missed some steps at the end of 30 some hour print 🙂
    I think I'll just solder the motor directly to the pins instead of using connectors.

    We are all on Duet ethernets, haven't tested Duet 3.
    Anybody close to 4A currents on the motors with Duet 3?

  • Moderator

    @DuetUser This definitely doesn't seem to be widespread. What else is in your environment that may contribute? Vibration? Moisture? Corrosion?

  • administrators

    @DuetUser said in Stepper Motor Connector scroched/overheated:

    We use NEMA 24 motors for Y and Z axes with current set to 1.5 A and overheating pins are very common.

    Overheating pins at currents well below the rated current are usually caused by bad crimp connections, or by using the wrong crimps. Are you using the crimp pins and header shells that we supply? What crimp tool are you using?

    I have on very rare occasions seen bad solder joints between the connector and the PCB cause this.

    Duet 3 uses a different connector, rated at a higher current.

  • @DuetUser I'm using nema17 and nema24 motors on few duet's and even on the PRC clones I don't see these issues not on 1.5A nor on 2A ...

    you are probably using bad cables (I had similar issues on some printers that came with iron and aluminium instead of copper cables, they just had a super thin layer of copper on them)

    you are for sure using either bad connectors or you crimped the connectors poorly. Even PRC connectors when crimped properly do not heat up at 2A, but even a high end connector, if you do not crimp it properly, will create issues, heat up and everything will go to ^#$%^$ ... if you are using those %$#@^ PRC cables the crimps on them can deteriorate over time (dunno if alu moves more due to heat or ..)

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