Motor phase is disconnected warnings



  • Hello all

    I've just migrated my extruder setup and started using Flex3Drive system.

    I'm using this OMC NEMA17 pancake stepper motor : https://www.omc-stepperonline.com/de/nema-17-bipolar-1-8deg-13ncm-18-4oz-in-1a-3-5v-42x42x20mm-4-drahte.html
    I'm using 13.6V as power source input with SSR for bed heating - so I think PSU handles everything just fine.

    I'm using the Duet Wifi with the latest Duet Firmware (2.03) with Duex5 board (the motor is connected to Duet though).

    Here is my config:

    M350 E8 I0
    M350 X16 Y16 Z16 I1                                                     ; Configure microstepping with interpolation
    M92 X80.00 Y80.00 Z800.00 E1900                                         ; Set steps per mm flex3drive
    M566 X900.00 Y900.00 Z60.00 E6.00                                       ; Set maximum instantaneous speed changes (mm/min)
    M203 X10500.00 Y10500.00 Z600.00 E2400.00                               ; Set maximum speeds (mm/min)
    M201 X1200.00 Y1200.00 Z300.00 E120.00                                  ; Set accelerations (mm/s^2)
    M906 X1000.00 Y1000.00 Z900.00 E400.00 I35                              ; Set motor currents (mA) and motor idle factor in per cent
    

    When I tell the extruder to move with 10 mm/sec or below, no problem there; however when I try to move them with 15mm/sec, motor rotates but I get 'Motor phase A disconnected' and 'Motor Phase B disconnected' warnings; at least twice in a 100mm extrusion.

    Since Flex3Drive uses high gearing, it's very hard to see if motor is skipping steps or something but I was wondering why could I be getting these warnings; how can I make them go away etc.

    How does chip detect this situation?

    Another thing is: when I make 100mm extrusion with 1 mm/sec speed, it generally extrudes about 85 mm - this seems very low to me. Could the motor be skipping indeed?

    I only used this motor with Titan extruder before and it seemed OK to me but I'm no motor expert so I wouldn't know. And before you asked: it doesn't make weird noises or anything when running.


  • administrators

    @ahmetipkin said in Motor phase is disconnected warnings:

    however when I try to move them with 15mm/sec, motor rotates but I get 'Motor phase A disconnected' and 'Motor Phase B disconnected' warnings; at least twice in a 100mm extrusion.

    The chip detects that there has been no chopper activity for a certain length of time even though steps have been commanded. My guess is that the combination of high motor speed (due to the high gearing and hence high steps/mm of the Flex3drive) requires more motor supply voltage than you have available. You can use the motor EMF calculator at https://reprapfirmware.org/ to check.

    Unless you have a Volcano hot end, it's unlikely that you will need to extrude faster than 5mm/sec.

    @ahmetipkin said in Motor phase is disconnected warnings:

    Another thing is: when I make 100mm extrusion with 1 mm/sec speed, it generally extrudes about 85 mm - this seems very low to me. Could the motor be skipping indeed?

    I think that's unlikely.



  • @ahmetipkin said in Motor phase is disconnected warnings:

    Flex3Drive

    I agree that going to 24V will certainly help a lot.

    Things you can try first.
    Increase the current. You are running your motor at 400mA while its a 1A motor.
    Try 800mA. This could help with skipped steps.

    Do you have other stepper motors?
    See if they can reach higher speeds than that pancake motor using this calculator.
    https://www.daycounter.com/Calculators/Stepper-Motor-Calculator.phtml



  • Thanks for the answers

    I've ordered the 24VPSU, Heating cartridge and the fans but they won't be arriving until next month. I'll check it with them as well..

    I was planning to switch due to resume-after-power-loss but it seems I gotta do it sooner 🙂

    I'll try increasing the current and check again 😉

    ReprapCalculator shows this results for 15 mm:

    Approximate peak back EMF due to rotation per motor: 10.3 V at 15.0 mm/s
    Approximate peak back EMF due to inductance per motor: 10.1 V at 15.0 mm/s
    

    So, does it mean I'm OK with 11 V supply, or do I need 10.3+10.1 = 20.4 V supply? If second then 10mm/sec is absolute limit for me (it shows 6.9 + 6.7 = 13.6 - exactly at the limit)


  • administrators

    The calculator will tell you the maximum speed you can achieve without loss of torque, at both high and low slip angle. What answers does it give?


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