Z-Axis correctly homing but crashes into the endstop on printing
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starts the g-code file, then it moves to the center in X and Y and then it moves the Z-axis (I've even increaten from Z0.3 to Z0.6) but is still can watch how the platform hits the Z-axis enstop but carelessly continues to move upwards.
Anyway you can post a video of this happening?
Is your Z home position down at the print bed where the nozzle touches the build plate or up with the nozzle at it highest point away from the build plate?
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Here is a short video. You can clearly see that i the beginning the Z-axis correctly stops when the endstop triggers, but when it moves to the middle you can hear that the Z-axis turns further even though the endstop triggers.
https://youtu.be/93f6WJ-Ht1IThis is the test G-Code file:
[[language]] ;Generated with Cura_SteamEngine 2.4.0 G21 ;metric values G90 ;absolute positioning M82 ;set extruder to absolute mode M107 ;start with the fan off G28 X0 Y0 ;move X/Y to min endstops G28 Z0 ;move Z to min endstops G1 Z15.0 F600 ;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 ;Put printing message on LCD screen M117 Printing... ;LAYER_COUNT:199 ;LAYER:0 M107 G1 F1500 E-6.5 G0 F3600 X86.3 Y86.301 G0 F600 Z0.6 ;End of Gcode -
What is in your homing gcode files?
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[[language]] ; homeall.g ; called to home all axes ; ; generated by RepRapFirmware Configuration Tool on Thu Nov 17 2016 21:40:07 GMT+0100 (W. Europe Standard Time) ; Relative positioning G91 ; Lift Z G1 Z5 F6000 ; Move towards X and Y axis endstops (first pass) G1 X-215 Y-215 F1800 S1 ; Go back a few mm G1 X5 Y5 F6000 ; Move slowly to axis endstops once more (second pass) G1 X-215 Y-215 F360 S1 ; Move Z down until the switch triggers G1 Z-210 S1 F1800 ; Absolute positioning G90 ; Tell the firmware where we are G92 Z2.5 ; Uncomment the following line to lift the nozzle after probing ;G1 Z5 F100[[language]] ; homez.g ; called to home the Z axis ; ; generated by RepRapFirmware Configuration Tool on Thu Nov 17 2016 21:40:07 GMT+0100 (W. Europe Standard Time) ; Lift Z relatively to current position G91 G1 Z5 F6000 ; Move Z down until the switch triggers G1 Z-210 S1 F1800 ; Back to absolute positioning G90 ; Tell the firmware where we are G92 Z2.5 ; Uncomment the following lines to lift Z after probing ;G91 ;G1 Z5 F100 ;G90 -
Your video is marked private, can't see it.
The line G92 Z2.5 after your homing sequence tells Duet your hotend is 2.5mm above the build plate while it is actually hitting the min-z endstop
If you go below Z2.5 afterwards the hotend will always move lower than when it hit the endstop (as in G0 F600 Z0.6 in your test)
Is that what you intend to do? -
I had nearly exactly the same issue, and I started discussing on on reprapforums:
http://forums.reprap.org/read.php?416,745331I fixed the issue by downloading a new configuration file (using exactly the same parameters). I've no idea what caused the first problem.
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made the video public.
Well then i might try that as well with uploading a new config file with same parameters. -
Before you overwrite everything, it is better to understand how it works so that you will be able to troubleshoot future problems.
Start with removing the G92 Z2.5 line from the files and see what happens -
or even make the value for Z in that line to be negative just to give a margin of safety that change should make the nozzle 2.5 above the bed
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What has been throwing me is the title which starts "Z axis correctly homing…" but now I don't think it is homing correctly.
Here is a quick explanation of how it works. Z=0 is the point where the nozzle is just touching the bed. We have some sort of probe or switch or whatever which will trigger when the bed gets close to it. However, it is very unlikely that the nozzle will be just touching the bed at this exact same position. It is possible but would require some very precise mechanical adjustment. So instead, we accept that the position where the switch/probe triggers is not Z=0 but is offset by some amount. Lets say the switch triggers 1.0 mm before the nozzle touches the bed. We then put this value into our configuration file which "tells" the machine that to get to Z =0 from the point where the switch triggers, we have to move a further 1.0mm.
It seems to me that the trigger height is set to 2.5mm in the config.g file but the true distance between the switch triggering and the nozzle touching the bed is somewhat less. So the machine tries to move 2.5mm from the point where the switch triggers because that is what it has been "told" is the distance from this point to Z =0.
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Ian, I totally agree with you.
I think some of these config files are generated by the online configuration tool, which may be misused by entry users.
A review/rewrite maybe required to generate suitable config files. -
Yes, it seems that this was the issue. I've used the tool at reprapfirmware.org but I still don't really understand what the difference is between "Trigger height at Z axis" and "Trigger height on bed" which are shown when i chose de Switch Tab in the Z-Probe section. Both their tooltips are the same and it seems to me that their value should be the same too, so why do I have to configure both?
Anyway, I got it almost working by manually adjusting the configuration file, but on the first try to print something, it failed because the hotend temperature sensor failed. i had the turn the printer off and on again in order to get it working again. Sadly after it failed a second time it went into reading 2000 degress since then. I'm using a PT-100 sensor and the daughter board and i even switched to the second RTD Pin but it's still reading 2000degrees. I've even replaced the sensor with no luck. Could it be that the daughter board is broken now or might it be the Duet itself?
