Has my Duet Wifi failed? Fixed



  • My Duet Wifi powered AM8 has been working perfectly for over a year. In the last week it has been doing 15 hour days printing a bunch of model tanks. The attached photo shows the second to last print alongside the last print.

    In between the two prints I had given the detachable glass bed a good clean and then re leveled and ran a Mesh Grid Compensation that came up all green. I then started printing the 2nd item. The first layer was the best I have seen in a long time but then about half way through the print the nozzle started to drag across parts of the print. It was almost as though the Z axis had stepped down a level rather than up to the new level.

    I stopped the print cleaned everything up, restarted the printer and stared a new print. A few seconds in the Z steppers (2 off) started graunching badly.

    If I now try to home the machine, the Z steppers graunch loudly and don't move, The X axis homes fine and the Y axis now also graunches briefly, homes and then starts graunching again.

    I have physically disconnected both z steppers from the z axis and neither stepper responds to commands.

    Has my board failed?? If so, is there a remedy.

    ![0_1574644813347_AM8 Issues.jpg](Uploading 100%)


  • administrators

    Your file upload hasn't succeeded. Please try it again.

    It's unlikely that both Z and Y drivers have failed at the same time, unless it was because of over-voltage.

    I suggest you try commanding the Z and Y motors to move, then run M122 to get a diagnostic report. The stepper drive statuses and the voltage report may shed light on the problem. Also check whether any of the motor driver chips is getting hot.

    Also I suggest you use a multimeter to check for continuity of each phase of each Y and Z motor, measured from the Duet, to check that the connections are OK. A failed crimp connection that results in only one phase being energised will cause that graunching sound.



  • Thanks DC42 you were quite right that it was a cable issue. However, finding the problem was challenging as a continuity check with a multimeter didn't show up any problems. In addition with two Z steppers it was hard to know if either one or both had failed.

    By chance I came across the M564 S0 H0 command which allow moving an axis using the machine control without homing all axes first. With this I was first able to test each of the stepper motors with a known good cable. This confirmed two things. 1 That the Duet Board was working fine and 2. that all of the stepper motors were working fine.

    This also allowed me to confirm that the Z0 Cable and the Y cable had failed. Can I say that these connectors would have to be one of the poorest designs I have come across.

    Of note both Z steppers had to be connected for this check to work.


  • administrators

    I'm glad you tracked the problem down. Which connectors are you referring to?

    The usual way to test individual motor and driver pairs is to send G91 to select relative motion, then send G1 H2 moves. For example, G1 H2 X10 will move the X motor forward 10mm regardless of the current position or whether axes have been homed.



  • @Pierre52 said in Has my Duet Wifi failed? Fixed:

    Of note both Z steppers had to be connected for this check to work.

    If you only want to run one stepper on Z, you need to put the jumpers back on the ZB connector.

    Ian


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