Duet 2 Wifi: First layer too high. Not hardware related.
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@Streamline said in Duet 2 Wifi: First layer too high. Not hardware related.:
Edit:
About motor current, I have done a bit of research and finally found a spec-sheet for the LDO-42STH47-2504AC motors I am using. They are rated for 2.5A per phase. So 800mA is a bit low right? Unsure what I should set it to with a 24V PSU?
I'm unable to find a datasheet after a cursory search, do you have a datasheet on hand? Common practice is to set M906 to 85% of the rated stepper current (so in your case, ~2.1A).
Can you post a sample print file? First 5 or so layers should give us enough information.
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@Phaedrux said in Duet 2 Wifi: First layer too high. Not hardware related.:
set to ~60-85% of the rated max for the motor
I guess the driver takes input voltage into consideration? I'll set it to 2.1A then.
@sebkritikel said in Duet 2 Wifi: First layer too high. Not hardware related.:
I'm unable to find a datasheet after a cursory search, do you have a datasheet on hand? Common practice is to set M906 to 85% of the rated stepper current (so in your case, ~2.1A).
Yes, here:
https://drive.google.com/open?id=1UDBD8BTQWq4__84nZrEikKAiVsDGqI-3
Found it on a french website that sells the motor.
Can you post a sample print file? First 5 or so layers should give us enough information.
First 5 layers of the testcube I printed this morning, I hope external links are OK:
https://drive.google.com/open?id=1HohdGKb9zibHRC15CTzHSTeWIl-YqZAL
Which resulted in the following part where I didn't do any babystepping. As you can see, the first layer is way too shallow and lines barely stuck to the bed. However, the next layers are mushed onto each other until the issue resolves itself after enough layers were printed. Which can be seen in the Z on the bottom, which should be clean in the middle but has some lines in it that also stuck to the bed.
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@Streamline said in Duet 2 Wifi: First layer too high. Not hardware related.:
I guess the driver takes input voltage into consideration?
Yes, you don't need to worry about the voltage.
@Streamline said in Duet 2 Wifi: First layer too high. Not hardware related.:
I hope external links are OK:
Yup, no problem.
Try again with increased motor current and see if it improves. Perhaps the Z axis is having some sticktion.
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Still the same. I will try to get the issue on video with an explanation.
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@Streamline I am no endstop specialist and a 3D print beginner, so please take the following information as rough ideas:
I really don't understand the meaning of the line
G1 Z15.0 F120 ;move the platform down 15mm
in the startup part, after homing, which is included in your sampleGcode also.(BTW G1 H1 Y315 ; then move slowly to Y axis endstop in the stampleCode is wrong, but has nothing todo with the problem, (s)low F is missing)
Are you sure the Z screw does not have a backlash problem when changing direction? If it's a V-Core Pro, it has three screws for Z movement also, so the bed could stuck as well (enlarging the backlash throught the friction). After the first layer printed, Z is moved into one direction only, so no more backlash effect.
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Yes, this is a V-Core Pro, but only with 2 lead-screws. I have different lead-screws though that seem to be better quality than the ones that come with the kit because as they are they already have less backlash. I have also adjusted the anti-backlash nuts so there is no play, but also close to no friction. I have also lubed the lead-screws.
@JoergS5 said in Duet 2 Wifi: First layer too high. Not hardware related.:
I really don't understand the meaning of the line
G1 Z15.0 F120 ;move the platform down 15mmThis moves the platform away from the nozzle by 15mm so that the nozzle can extrude a few mm of filament before starting to print so as to have a clean start. The bed and nozzle then move back together while the nozzle is moving to its first coordinates.
@Phaedrux said in Duet 2 Wifi: First layer too high. Not hardware related.:
Try again with increased motor current and see if it improves. Perhaps the Z axis is having some sticktion.
The increased motor current did increase print quality (little bit less ghosting), but the problem persists. I have recorded a video explaining the issue.
https://www.youtube.com/watch?v=mtcjGbymnV4&feature=youtu.be
Here are two more screenshots where you can clearly see the difference in nozzle-height. Both are "0.3mm" from the bed, as displayed by the web interface. However, before the print looks like 0.3, and while printing it's much higher, looks like double the height:
Before print:
While printing:
This resulted in the following:
First layer from underneath, no adhesion
Next layers from above, too close, mushed layers since nozzle is dragging through the part
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@Streamline If I understand you correctly, the problem is that:
G1 H1 Z-255 F360 ; move Z down stopping at the endstop
G90 ; absolute positioning
G92 Z0
;homing done
G1 Z15.0 F120 ;move the platform down 15mm
G92 E0 ;zero the extruded length
G1 F200 E6 ;extrude 6 mm of feed stock
G92 E0 ;zero the extruded length again
G1 F120
M83 ;relative extrusion mode
G1 F1500 E-2
;LAYER_COUNT:99
;LAYER:0
M107
G0 F3600 X133.403 Y143.255 Z0.3doesn't move to Z0.3, but to Z0.5
Could you try to abbreviate the code to:
G1 H1 Z-255 F360
G90
G92 Z0
G0 F3600 X133.403 Y143.255 Z0.3and check that it is also wrong 0.5? Maybe with a slow speed to exclude mechanical reasons like vibrations. And as first test, not moving X and Y to exclude an uneven or tilted print bed or up-bended X axis.
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The lines you suggested did not work, but I excluded the 15mm raise and extrude stock filament lines in the start-code and this might have done the trick for the first layer.
Next layers still appear to be mushed down, but I think that might be my aggressive leveling, which is pretty low to the bed, which is also apparent when removing the printed part, the first layer is way too close to the bed now.
I have a BLTouch on the way, so this will resolve that issue anyway.
However, I am still interested in why the 15mm raise is making problems, because it is neat to be able to extrude some filament before the print, so one can start with a clean line.
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@Phaedrux said in Duet 2 Wifi: First layer too high. Not hardware related.:
Try again with increased motor current and see if it improves.
Here's another question:
As I am using two Z motors, which are wired in series, does that mean I need to double the current in the firmware? I didn't find any mention of this in documentation, but that's how it had to be done on my old Wanhao i3.
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@Streamline If you use two steppers for Z, each time you power up the steppers' positions can be different, up to about 2 full steps for each one in every direction, 4 in total in worst case. This results in a tilted distance to the bed and/or stuck Z movement. The print bed, if you have the configuration with 4 screws, is very stiff and little tilting or thermal expansion will result in stuck effects with backlash if direction of the Z axis changes. You had M107 additionally in the short G-Code, so maybe there is an additional thermal effect.
If you have a free motor controller on your board (maybe your second E is free), you can address both steppers separately. The firmware supports the assignment of both stepper/controllers to one axis Z and a separated calibration of the two steppers at startup and later movement together.
There is explicit documentation for it: https://duet3d.dozuki.com/Wiki/Bed_levelling_using_multiple_independent_Z_motors
An alternative is to use one stepper for Z and drive a belt which is connected to both spindles.An additional problem is steppers in serial: the 800 mA current flows through both of course, but voltage is split. No two steppers are really identical, so they differ in voltage and behavior.
An additional possibility is a problem of the coupling between stepper and spindle, which type is it? The aluminium ones with diagonal interruptions can produce backlash.
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Couple things:
In your homing file you move to the Z endstop and set the position to Z0. But is the nozzle actually touching the bed at that point?
After homing if you command the Z axis to Z0 with
G90 G1 Z0does the nozzle touch the bed or is it above?If removing the 15mm move helps the situation that would indicate again that there is some binding in the Z axis.
Also, as @JoergS5 says, when you have multiple z motors that aren't mechanically linked together they will drift apart over time. Using independant Z motors and a probe to return them to a match position is a good software solution. Using a belt to link them is a good mechanical solution.
If you are using the dual Z connector for the Z motors they are wired in series internally, so you only need to set the current as you would for a single motor. They are getting half voltage though, so there is a limitation. If you have a free driver (E1 perhaps) you can use independent steppers which will give best performance to the motors, but that doesn't solve the problem of getting out of sync or binding.
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Thank you both so much, I learned a lot in this thread.
I will look into driving both Z motors independently, or in the future drive the whole Z axis with only one motor, or somehow get both motors to synch up.
I have also observed the couplings (yes, the springy kind) and they do introduce backlash when moving up with the bed coming to a stop. I have introduced a second, slower, homing move to compensate for this. I know about plum-couplings, and they should be better than the springy ones right?
Also waiting for my BLTouch to arrive.
For now I can print pretty reliably with how I have it set up. However I want to reintroduce the 15mm distancing to extrude some filament before printing. It's a very clean way to start a print.
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@Streamline nice to know that you found some solutions.
A good not too expensive replacement of the couplers are the "dog clutch" (called Rotex, or spider, or jaw also) couplings*). There were discussions in this forum at
https://forum.duet3d.com/topic/6841/rigid-vs-flexible-couplers-for-trapezoidal-leadscrews
and
https://forum.duet3d.com/topic/7424/spider-coupling-for-lead-screw -
@Streamline said in Duet 2 Wifi: First layer too high. Not hardware related.:
However I want to reintroduce the 15mm distancing to extrude some filament before printing. It's a very clean way to start a print.
I use a short thick extrusion line at the corner of the bed to prime the extruder and clean the nozzle. It gets called from the start gcode.
;M98 P"0:/sys/PrimeNozzle.g" G90 ; Absolute positioning G1 X1 Y270 F6000 ; Move to rear left corner M400 ; clear movement buffer M116 ; Wait for temps G1 Z0.3 F100 ; Move Z to prime height G91 ; Relative positioning M83 ; Relative extrusion G1 X40 E10 F300 ; Prime nozzle G10 ; Retract G1 Y-1 X1 F10000 ; Wipe nozzle M400 -
Thanks for the script, I will try it out.
I have further investigated the issue, and finally did realize, that the Z axis is binding at the top and first few mm of movement: moving the bed up or down by 0.5mm at the very top resulted in 0 movement. Replaced the springy couplings with solid ones that I had laying around, installed my BLTouch and it seems to now be working reliably. Still some work to do, but at least I can start a print without worries now.
I will rework my frame and look if there's any issues there, probably also get spider/rotex/plum couplings.
I also put my second Z motor on E1, which works great and will allow me to get tilt compensation working in the future.
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Glad you found it! Might want to edit the title to be "Ok turns out it was hardware related."
