Stepper motor dead?



  • I am setting up duet for the first time.
    my machine uses 6 stepper motors.
    one y-axis motor 2.3A rated current (ok42sth60-2304a)
    I set the current to 1.8A.
    it was working fine when I was testing movements,
    then I increased the speed from pronterface and tried running it.
    it just vibrated and didn't turn. other motors worked fine.
    reconnected everything. same problem.

    checked the continuity of coils. red and blue wires are not continuous. (fried?)
    could increasing the speed cause this?

    config.g

    ; Configuration file for testing Duet Ethernet and Wifi

    ; Communication and general

    M111 S0 ; Debug off

    M550 Sculptbot ; Machine name and Netbios name (can be anything you like)

    M551 3dparadise ; Machine password (used for FTP)

    M552 S1 ; Turn network on

    ;
    M555 P2 ; Set output to look like Marlin

    M575 P1 B57600 S1  ; Set auxiliary serial port baud rate and require checksum (for PanelDue)

    G21 ; Work in millimetres

    G90 ; Send absolute coordinates…

    M83 ; ...but relative extruder moves

    ; Disable Fan 1 thermostatic mode

    M106 P1 H-1

    ; Axis and motor configuration

    M569 P0 S1 ; Drive 0 goes forwards

    M569 P1 S1 ; Drive 1 goes forwards

    M569 P2 S1 ; Drive 2 goes forwards

    M569 P3 S1 ; Drive 3 goes forwards

    M569 P4 S1 ; Drive 4 goes forwards

    M574 X1 Y1 Z0 S1 ; set endstop configuration (all endstops at low end, active high)

    ;*** The homed height is deliberately set too high in the following - you will adjust it during calibration

    M906 X1700 Y1950 Z1700 E1130:1130 I60 ; Set motor currents (mA) and increase idle current to 60%

    M201 X800 Y800 Z15 E1000            ; Accelerations (mm/s^2)
    M203 X10000 Y10000 Z800 E3600       ; Maximum speeds (mm/min)
    M566 X200 Y200 Z20 E20              ; Max Jerk speeds mm/minute

    M208 X200 Y200 Z200  ; set axis maxima and high homing switch positions (adjust to suit your machine)
    M208 X-2 Y-2 Z-0.2 S1   ; set axis minima and low homing switch positions (adjust to make X=0 and Y=0 the edges of the bed)
    M92 X80 Y80 Z1600  ; set axis steps/mm
    M92 E418.5:418.5  ; set extruder 0 and 1 steps/mm
    M350 X128 Y128 Z128 E128:128   ; set microstepping128

    ;z probe
    M558 P4 X0 Y0 Z1 H8 F200 T5000 R0 ; smart IR Z probe, used for homing Z axis only, dive height 3mm, probe speed 200mm/min, travel speed 5000mm/min, no recovery time
    G31 P300 X11.0 Y0.5 Z1.65  ; set threshold and offsets

    Thermistors

    M305 P0 ; Put your own H and/or L values here to set the bed thermistor ADC correction

    M305 P1 X100 ; Put your own H and/or L values here to set first nozzle thermistor ADC correction

    M305 P2 ; Put your own H and/or L values here to set 2nd nozzle thermistor ADC correction

    M570 S180 ; Hot end may be a little slow to heat up so allow it 180 seconds

    ; Adjustments for J-heads used as dummy heaters on test rig

    M563 P0 D0 H1 ; Define tool 0

    G10 P0 S0 R0 X-50 Y0 ; Set tool 0 operating and standby temperatures

    M563 P1 D1 H2 ; Define tool 1

    G10 P1 S0 R0 X50 Y0 ; Set tool 1 operating and standby temperatures

    ;M307 H0 A250 C140 D5.5 B1

    ;M307 H1 A250 C140 D5.5 B0

    ;M307 H2 A250 C140 D5.5 B0

    ; Fans

    ;M106 P1 S-1 ; disable thermostatic mode for fan 1

    ; Tool definitions

    ;M143 H0 S135 ; Maximum temperature - Heated bed , default is 125C
    ;M143 H1 S290 ; Maximum temperature - Right extruder, default is 262C
    ;M143 H2 S290 ; Maximum temperature - Left extruder, default is 262C

    ;*** If you are using axis compensation, put the figures in the following command

    M556 S78 X0 Y0 Z0 ; Axis compensation here

    ;M208 S1 Z-0.2 ; set minimum

    T0 ; select first hot end



  • It's not common for a stepper to die, but if there are not two connected pairs of coils then it's a dead motor. More importantly, check the duet board stepper driver chip for that motor channel and make sure it doesn't have any visual evidence of a hole or pit on the top casing, or that it doesn't get very hot when powered up. Swap a known good motor onto that channel and test it. It might be a driver chip failure that killed the motor, which is a more expensive problem to rectify. A new motor is not a particularly big problem.

    My understanding is that high speed does not necessarily place more demand on motors electrically than when moving slowly. In slow movement they are still using all the energy supplied (its constant current remember) to hold position; when moving fast the current remains the same but the switching from one coil to the next occurs faster. If you greatly increased the current before it failed that could explain it.



  • thanks for the information DjDemonD.
    stepper driver is working fine.
    I want to know what can fry a stepper motor other than current. (current was well below the rated current).
    running duet with a 24V supply.
    how does a stepper motor run with a 24v and 12v with same rated current? (I have very basic knowledge of motors)



  • what should be the rated voltage for stepper motor if I'm using a 24V supply?
    documentation says less than 3V. can someone explain this?



  • I am not an expert DC is the motor expert around these parts, but my understanding is that the amount of time the current is applied to a coil is less at higher voltage. So at 12v you need a longer pulse of power to move the motor 1 step (or microstep) than at 24v, but the current applied is the same. I am quite sure the real explanation is way more complex than my interpretation.

    Th voltages on the motor specs are not directly related to the voltage you drive them with. There is a relationship but have a dig around my understanding is you want to be a good way above the voltage rated on the motor to get good operation if you are close to it or lower than it, it doesn't work well.

    In any case what can cause it to fail - badly made motor would be my best guess. It could be there was a slight intermittent connection between the motor and duet, whilst these later duet boards are designed to survive this the motors may not, as this causes high voltage spikes which is why it is never recommended to disconnect a motor when powered up.



  • thanks for the help.
    there is no logical explanation to say that motor fried because of an increase in speed (from pronterface).
    and motor stopped working right after I increased the speed.



  • Not that I am aware of, coincidence. The motor is working hard when its holding position, as the coils are energised, making it go faster is just alternating the current to the coils to make it spin rather than hold.



  • Some sort of PWM is used to regulate the current through stepper's coils with different supply voltages. TMC2660 has 2 type of PWM not sure which one is used in Duet firmware. Rated voltage is the max voltage that can be applied when driving the stepper in pure voltage mode when current through a coil is limitted by its resistivity (multiply Imax by Rcoil and you get it). BTW how do you check that the driver chip is OK, visually? It is a chance that driver's nMOS switches got short to VIN and/or GND and they fried the coil so it is wise to check driver's chip with a multimeter. PWM in standstill is static for coils in stepper while when fast moving there is constant changing in driving pulse width so many transient events that might provoke the fail (bad electric contacts could give that for example).


  • administrators

    Are you certain that the problem isn't in the crimp connections to the stepper motor wires?



  • @dc42:

    Are you certain that the problem isn't in the crimp connections to the stepper motor wires?

    yes I'm certain. it was working fine before.
    i extended the wires using solder and heat shrink.



  • @zov:

    Some sort of PWM is used to regulate the current through stepper's coils with different supply voltages. TMC2660 has 2 type of PWM not sure which one is used in Duet firmware. Rated voltage is the max voltage that can be applied when driving the stepper in pure voltage mode when current through a coil is limitted by its resistivity (multiply Imax by Rcoil and you get it). BTW how do you check that the driver chip is OK, visually? It is a chance that driver's nMOS switches got short to VIN and/or GND and they fried the coil so it is wise to check driver's chip with a multimeter. PWM in standstill is static for coils in stepper while when fast moving there is constant changing in driving pulse width so many transient events that might provoke the fail (bad electric contacts could give that for example).

    i connected another motor to the same driver and it worked. still waiting for my replacement to come.

    how do i make sure its not the driver before i fry another motor.



  • If another motor worked then it is almost surely not a driver fault. As David said it could be intermittent crimp connections so check them twice before using a new motor. After all it could be just a bad quality motor.


Locked
 

Looks like your connection to Duet3D was lost, please wait while we try to reconnect.