Problems with Z axis steppers

[yagodajm]

I have been trying to figure out why my Z axis will never stay level. I thought at first is was binding on the linear rails. But I took the whole X axis off and looked at the Z axis motors running. The attached video is what is happening when I send a plus 50mm to the Z axis. Both motors start, then the right stops and the left goes, then the right starts back up. Any ideas what is going on, this is the first time I am seeing this problem. Each motor is attached to the Duet Maestro board on the two Z axis plugs.

Here is the my current config.g

; Configuration file for Duet Maestro (firmware version 3)
; executed by the firmware on start-up
;
; generated by RepRapFirmware Configuration Tool v3.1.1 on Thu Jun 04 2020 15:43:41 GMT-0500 (Central Daylight Time)
 
; General preferences
G90                                                ; send absolute coordinates...
M83                                                ; ...but relative extruder moves
M550 P"My Printer"                                 ; set printer name
 
; Network
M552 P0.0.0.0 S1                                   ; enable network and acquire dynamic address via DHCP
M586 P0 S1                                         ; enable HTTP
M586 P1 S0                                         ; disable FTP
M586 P2 S0                                         ; disable Telnet
 
; Drives
M569 P0 S0                                         ; physical drive 0 goes backwards
M569 P0 V30					   ; Stealthchop2 till about 150 mm/sec
M569 P1 S1                                         ; physical drive 1 goes forwards
M569 P2 V30					   ; Stealthchop2 till about 150 mm/sec
M569 P2 S1                                         ; physical drive 2 goes forwards
M569 P2 V30					   ; Stealthchop2 till about 150 mm/sec
M569 P3 S1                                         ; physical drive 3 goes forwards
M569 P3 V30					   ; Stealthchop2 till about 150 mm/sec
M584 X0 Y1 Z2 E3                                   ; set drive mapping
M350 X16 Y16 Z16 E16 I1                            ; configure microstepping with interpolation
M92 X80.00 Y80.00 Z400.00 E90.00                   ; set steps per mm
M566 X900.00 Y900.00 Z12.00 E120.00                ; set maximum instantaneous speed changes (mm/min)
M203 X300000.00 Y300000.00 Z6000.00 E216000.00     ; set maximum speeds (mm/min)
M201 X800.00 Y800.00 Z15.00 E1000.00               ; set accelerations (mm/s^2)
M906 X1000 Y1000 Z1000 E1000 I30                   ; set motor currents (mA) and motor idle factor in per cent
M84 S30                                            ; Set idle timeout
 
; Axis Limits
M208 X0 Y0 Z0 S1                                   ; set axis minima
M208 X200 Y200 Z200 S0                             ; set axis maxima
 
; Endstops
M574 X2 S1 P"!xstop"                               ; configure active-high endstop for high end on X via pin !xstop
M574 Y1 S1 P"!^ystop"                              ; configure active-high endstop for low end on Y via pin !^ystop
M574 Z1 S2                                         ; configure Z-probe endstop for low end on Z
 
; Z-Probe
M950 S0 C"^zprobe.mod"                             ; create servo pin 0 for BLTouch
M558 P9 C"zprobe.in" H5 F120 T6000                 ; set Z probe type to bltouch and the dive height + speeds
G31 P500 X33 Y5 Z1.9                               ; set Z probe trigger value, offset and trigger height
M557 X15:200 Y15:195 S20                           ; define mesh grid
 
 
; Heaters
M308 S0 P"bedtemp" Y"thermistor" T100000 B3950 R2200    ; configure sensor 0 as thermistor on pin bedtemp
M950 H0 C"bedheat" T0                              ; create bed heater output on bedheat and map it to sensor 0
;M307 H0 B1 S1.00                                   ; enable bang-bang mode for the bed heater and set PWM limit
M140 H0                                            ; map heated bed to heater 0
M143 H0 S120                                       ; set temperature limit for heater 0 to 120C
M308 S1 P"e0temp" Y"thermistor" T100000 B3950 R2200     ; configure sensor 1 as thermistor on pin e0temp
M950 H1 C"e0heat" T1                               ; create nozzle heater output on e0heat and map it to sensor 1
;M307 H1 B0 S1.00                                   ; disable bang-bang mode for heater  and set PWM limit
M307 H0 M307 H1 A306.3 C136.3 D4.5 B0    ;  This is to prevent heater fault
 
; Fans
M950 F0 C"fan0" Q500                               ; create fan 0 on pin fan0 and set its frequency
M106 P0 S0 H-1                                     ; set fan 0 value. Thermostatic control is turned off
M950 F1 C"fan1" Q500                               ; create fan 1 on pin fan1 and set its frequency
M106 P1 S1 H1 T45                                  ; set fan 1 value. Thermostatic control is turned on
 
; Tools
M563 P0 D0 H1 F0                                   ; define tool 0
G10 P0 X0 Y0 Z0                                    ; set tool 0 axis offsets
G10 P0 R0 S0                                       ; set initial tool 0 active and standby temperatures to 0C
 
; Custom settings are not defined
 
; Miscellaneous
M911 S10 R11 P"M913 X0 Y0 G91 M83 G1 Z3 E-5 F1000" ; set voltage thresholds and actions to run on power loss
T0                                                 ; select first tool
 

Stepper video

thanks,
Justin

[zapta]

@yagodajm, what VIN are you using? (12V? 24V?). Also, what happens if you run the same experiment but with slower Z movement (e.g. 5 times slower)?

[yagodajm]

I am running 12 V.

[zapta]

@yagodajm, IIRC the dual Z plugs connect the steppers in series such that each has in average only 6 volts and once can affect the other. There is some discussion here https://duet3d.dozuki.com/Wiki/Choosing_and_connecting_stepper_motors

Do you have the spec of the steppers you are using (inductance, resistance, etc)?

Try to run the experiment at lower speed, if the steppers will behave more reasonably it may be a voltage issue.

Another experiment is to connect just one motor at a time (install the two jumpers on the board for the other stepper), and see if it works as expected. Again, this will indicate a voltage issue.

[yagodajm]

@zapta said in Problems with Z axis steppers:

you
OK, so if I install a 24 v power supply, that means I have to use a 24v hot end and bed,correct? I am thinking this is the way I need to go.

[yagodajm]

This is the info on my steppers

Model: 42SHD0001-24 Step Angle: 1.8° Number Of Phase :2 Insulation Resistance : 100MΩmin.(500V DC) Insulation Class : Class B Rotor Inertia : 38g.cm^2 Mass : 0.2kg Rated Voltage : 12V Rated Current : 0.4A Resistance Per Phase : 30Ω±10% Inductance Per Phase: 37mH±20% Holding Torque : 260mN.m Detent Torque : 12mN.m

Can I put 24v tonthese ?

[zapta]

@yagodajm said in Problems with Z axis steppers:

12V Rated Current : 0.4A Resistance Per Phase : 30Ω±10%

This stepper doesn't look as a good fit for 12V system with two steppers in series. You want a lower resistance and higher current stepper (ignore that voltage specification of the stepper, it doesn't matter).

Let's see if anybody here will come with a recommendation for a stepper.

[aidar]

Until you get better steppers, you can try to connect second Z motor to E1 (and of corse config it properly), that way they are not connected in series at least.

[yagodajm]

Do you have any recommended steppers to use with the duet maestro?

[yagodajm]

Do either of these work? I am thinking the first one because of the current rating on the duet maestro.

Nema 17 stepper motor with step angle 1.8deg
Holding Torque: 45Ncm(63.74oz.in), 12-24 VDC
Rated Current/phase: 1.50A & Phase Resistance: 2.3ohms

---

Motor Type: Bipolar Stepper

• Step Angle: 1.8 deg.
• Holding Torque: 59Ncm(83.6oz.in)
• Rated Current/phase: 2.0A
• Phase Resistance: 1.4ohms
• Inductance: 3.0mH+/-20%(1KHz)

If I use these, do I still need to switch power supplies to 24 v ?

Thanks,
Justin

[zapta]

@yagodajm, the spec of this 1.4OHM stepper looks much better. Let's see what they expert here say regarding 12V vs 24V.

There are stepper motor calculators. E.g. this one.

https://www.allaboutcircuits.com/tools/stepper-motor-calculator/

[yagodajm]

@zapta
I am just worried with the current on the second one. The maestro Max's out at 1.6, I believe it is to much?

[Phaedrux]

Those motors would be a better fit. The rated current is ok for the maestro as you'd be using 70-85% of rated current.

24v is always better choice than 12v if possible, but keep in mind that requires 24v heater and fans (though fans you can use a buck converter to provide 12v).

[yagodajm]

Everyone, thanks for all of your help, I went a head and ordered the

Motor Type: Bipolar Stepper

Step Angle: 1.8 deg.
Holding Torque: 59Ncm(83.6oz.in)
Rated Current/phase: 2.0A
Phase Resistance: 1.4ohms
Inductance: 3.0mH+/-20%(1KHz)

At what ma should I run them at, around 1400ma?

thanks,
Justin

[Phaedrux]

1000 to 1400, but be sure to actively cool the board with a fan.

[yagodajm]

Got it, thanks for all of you help.

[Karma]

@yagodajm Partly Correct. It will be explained further down in this message.

The hotend part is a very easy part to replace. To save you some money, you can still use your 12V power supply to only power your 12V heatbed. That's until tou can get another heatbed that is 24V. Then again, some heatbeds are both 12V and 24V. It all depends on how you connect the heatbed. It will say that on the heatbed itself.

There is a way to use your 12V hotend with the 24V system. There is a command that will allow you to limit the amount of voltage to lets say, the hotend, the fans, the heatbed as well.

If you are interested with what I said above, just simple reply to my message.

Karma

[Phaedrux]

@Karma said in Problems with Z axis steppers:

There is a way to use your 12V hotend with the 24V system. There is a command that will allow you to limit the amount of voltage to lets say, the hotend, the fans, the heatbed as well.

Using PWM to "limit" the 24v power delivered to a 12v heater is not recommended. PWM means that it's just switching the power on and off very rapidly. So it's still getting 24v sent to a 12v heater, it's just off half the time. In a normal situation this can lead to premature heater failure. In a failure situation where full power is applied this is very dangerous. Not worth saving a few dollars.

[Karma]

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[Karma]

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