inconsistent Z movement
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Hello
I'm having some issues with my printers Z movement and looking for some advice as I've been unable to resolve it after a few days of troubleshooting.
Printer is a cartesian, started life as an Anet A8 which i changed to a metal frame (AM8) some time ago. I then switched to a Duet 2 wifi mainboard this past December and got it all setup and running reliably. The only thing left original from the A8 was the steppers.
A couple weeks ago, i changed a lot of things:
- Converted from 12V to 24V
- Linear rails on all Axis (BLV MGN mod for AM8)
- New Stepper motors (these)
- Changed Bowden setup to a geared direct drive extruder
I made any required changes to the config, everything seems to work like it should except i can't get anything to consistently stick to the bed. I'm using a BL touch and have calibrated the trigger height a zillion times.
After troubleshooting a lot I've come to the conclusion that the Z axis isn't changing height consistently. Resulting in the nozzle being either too close or too far from the bed but it's not consistent.
For example, after calibrating the Z probe trigger height I'll home all axes, move the print head to the centre of the bed and move Z to zero. Often it is just slightly too high, when I use the web interface to jog Z down .05 mm my feeler gauge will no longer fit between the bed and nozzle. Still using the web interface I'll have to jog the z axis up multiple times using the .05mm button to get it to the right height. But then Z height is showing as .10mm.
It's a dual Z stepper setup, using the two Z connectors on the duet which i believe are in series.
At this point I'm at a loss. I've disassembled the gantry ensured everything is square, linear rails are parallel, and nothing is binding. Without the lead screws connected the gantry moves freely. I can move the Z axis up and down in large increments and i don't notice the steppers missing steps at all.
So I'm hoping someone's been here before and can guide me on what I should be looking at next.
Config.g
; Configuration file for Duet WiFi (firmware version 3) ; executed by the firmware on start-up ; ; generated by RepRapFirmware Configuration Tool v3.1.10 on Fri Dec 04 2020 11:06:48 GMT-0500 (Eastern Standard Time) ; General preferences G90 ; send absolute coordinates... M83 ; ...but relative extruder moves M550 P"3DP" ; set printer name ; Network M552 S1 ; enable network M586 P0 S1 ; enable HTTP M586 P1 S0 ; disable FTP M586 P2 S1 ; Enable Telnet ; Drives M569 P0 S1 ; X goes forwards M569 P1 S1 ; Y goes forwards M569 P2 S0 ; Z goes backwards M569 P3 S0 ; E0 goes backwards M584 X0 Y1 Z2 E3 ; set drive mapping M350 X16 Y16 Z16 E16 I1 ; configure microstepping with interpolation M92 X99.02 Y100 Z400 E418.06 ; set steps per mm M566 X600.00 Y600.00 Z18.00 E300.00 ; set maximum instantaneous speed changes (mm/min) M203 X6000.00 Y6000.00 Z180.00 E6000.00 ; set maximum speeds (mm/min) M201 X2000.00 Y2000.00 Z100.00 E10000.00 ; set accelerations (mm/s^2) M906 X1125 Y1125 Z1125 E1125 I30 ; set motor currents (mA) and motor idle factor in per cent M84 S30 ; Set idle timeout ; Axis Limits M208 X-17.5 Y-23.1 Z0 S1 ; set axis minima M208 X236 Y225 Z240 S0 ; set axis maxima ; Endstops M574 X1 S1 P"!xstop" ; configure active-low endstop for low end on X via pin xstop M574 Y1 S1 P"!ystop" ; configure active-low 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"exp.heater3" ; create servo pin 0 for BLTouch M558 P9 C"^zprobe.in" H5 R.25 F100 T6000 ; set Z probe type to bltouch and the dive height + speeds G31 P500 X-29 Y0 Z1.070 ; set Z probe trigger value, offset and trigger height M557 X10:231 Y20:200 S60 ; define mesh grid ; Heaters M308 S0 P"bedtemp" Y"thermistor" T100000 B4725 C7.06e-8 L-127 ; 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 A206.6 C640.6 D2.1 V24.4 B0 S1 ; disable bang-bang mode for the bed heater and set PWM limit M140 H0 ; map heated bed to heater 0 M143 H0 S130 ; set temperature limit for heater 0 to 130C M308 S1 P"e0temp" Y"thermistor" T100000 B4725 C7.06e-8 ; 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 A611.0 C193.4 D4.9 V24.4 B0 S1 ; disable bang-bang mode for heater and set PWM limit M143 H1 S275 ; set temperature limit for heater 1 to 275C ; 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 T0 ; select first tool -
Are you using those new motors on the Z axis as well?
Is this a new problem after those recent changes?
You can try bumping the motor current on the Z axis a bit. Try 1300ma.
How heavy is the gantry?
Have you squared up the gantry so that it's even on both sides? If you have a spare driver you could put each Z motor on it's own driver. (just add the second driver number to the M584 Z mapping, nothing else needs to change)
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@Phaedrux said in inconsistent Z movement:
Are you using those new motors on the Z axis as well?
Is this a new problem after those recent changes?
You can try bumping the motor current on the Z axis a bit. Try 1300ma.
How heavy is the gantry?
Have you squared up the gantry so that it's even on both sides? If you have a spare driver you could put each Z motor on it's own driver. (just add the second driver number to the M584 Z mapping, nothing else needs to change)
Thanks for your reply.
Yes i used those motors on the Z and this is only a problem after my changes. Prior to this everything was working reliably, i didn't have failed prints.
I will play with the motor current and see if that makes any difference.
I never weighed the gantry, previously it was a printed carriage with E3D hot end (bowden) on 2 smooth rods.After the change it's a piece of 2020 extrusion w/ linear rail, still printed carriage but direct drive. So it's definitely heavier... Just not sure how heavy.
Everything is square, i guess the last attempt will be to run each motor on its own stepper. But i did run the same configuration prior to the changes so I don't know if that's really the problem or not... But I'm not an expert.
Thanks again
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No progress really. I bumped up the current as much as i could while keeping the motors from getting hot (1375mA) but i still get the inconsistent Z movement.
Next step will be to try independent steppers for each Z motor. Time is limited to work on this but hopefully i can try and get that setup in the next 1-2 days
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@Phaedrux said in inconsistent Z movement:
M584
So i setup this up
M584 X0 Y1 Z2:4 E3But now i get this
G28 Warning: motor phase A may be disconnected reported by driver(s) 2 4 Warning: motor phase B may be disconnected reported by driver(s) 2 4Is this because now one motor from Z is disconnected? How do i fix that?
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What is connected to drivers 2 and 4?
Do you have the jumpers installed in the second Z port? -
@Phaedrux said in inconsistent Z movement:
What is connected to drivers 2 and 4?
Originally Each Z motor was connected to Z1/Z2 (driver 2), i moved one to E1 (Driver 4) for each to be on their own driver as you suggested
@Phaedrux said in inconsistent Z movement:
Do you have the jumpers installed in the second Z port?
I didn't realize in the wiring diagram that there was option A and option B. After seeing that i installed the jumpers and now both motors are moving.
So now new issue. Home x and Home Y lift Z by a few mm. I can see one Z motor is spinning faster than the other because one coupler expands... I doubt this is config related, what could potentially cause this, bad wiring?
Edit, I just realized they're spinning in opposite directions
Edit 2: Fixed that with M569 for driver 4. Will continue to test -
; Drives
M569 P0 S1 ; X goes forwards
M569 P1 S1 ; Y goes forwards
M569 P2 S0 ; Z goes backwards
M569 P3 S0 ; E0 goes backwardsAdd driver 4 to the list and set the direction
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Yeah i had caught that just after posting. Fixed it and all is good.
Preliminary testing using a feeler gauge is that the height movement is consistent, or at least more than it was before.
But I've been wondering. Prior to all my changes i ran 12V, with the original Anet A8 stepper motors, with the dual Z connected to Z1 and Z2 and never had this problem.
Is there something wrong with the new motors i bought? Should i be looking at just replacing the Z motors with something more suitable?
Thanks,
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The specifications of those motors look OK to me. Check that they move freely.
Duet WiFi hardware designer and firmware engineer
Please do not ask me for Duet support via PM or email, use the forum
http://www.escher3d.com, https://miscsolutions.wordpress.com -
As far as I can tell they do, and I've quadruple checked the linear rail alignment that the gantry moves freely up and down without binding.
The only other thing i can think of is that i also added anti-backlash lead screw nuts... They were generic off of amazon, maybe they're causing some kind of additional resistance.
I may end up disassembling/reassembling the whole thing and verifying all wiring as well because this is the first time I've been really stumped.
But after a few tests this morning the consistency seems more reliable with independent Z drives so I'm going to move onto the next problem.
Thanks,
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@kmart said in inconsistent Z movement:
maybe they're causing some kind of additional resistance.
That's typically what they do. Sometimes to the point of binding if the motor isn't powerful enough. Backlash is typically not a problem on Z. So I'd try removing them.
