Power recover wrong last position



  • Hi,

    I'm running duet wifi 24V 1.20beta6 for the firmware version.

    my sys/powerfail.g is:
    G91
    G1 Z3 F3000
    M83
    G1 E-4 F3600

    my sys/powerrestore.g is:
    M83
    G1 E4 F3600

    my sys/resurrect-prologue.g is:
    M116
    G28 X Y
    M83
    G1 E2 F3600

    my config.g line is:
    M911 S20.5 R22.0 P"M913 X0 Y0 G91 M83 G1 Z3 E-5 F1000"

    And my ressurect.g file after I shut down the printer is:
    ; File "cilindru5.gcode" resume print after print paused at 2017-11-06 13:04
    M140 S55.0
    G10 P0 S200 R0
    T0 P0
    M98 Presurrect-prologue.g
    M106 P0 S1.00
    M106 P2 S1.00
    M106 P3 S0.00
    M106 P4 S0.00
    M106 P5 S0.00
    M106 P6 S0.00
    M106 P7 S0.00
    M106 P8 S0.00
    M106 S255.00
    M116
    M290 S0.000
    G92 E0.00000
    M83
    M23 cilindru5.gcode
    M26 S48738 P0.000
    G0 F6000 Z5.771
    G0 F6000 X76.79 Y103.62
    G0 F6000 Z3.771
    G1 F6000.0 P0
    M24

    I don't know why but after i run ressurect.g file after power failure, the last position of the head is not accurate at all. Not even close. The head is like 5mm above the print and the start point on X and Y for printing the object is not the same as it was before power failing.

    The thing that is not exactly the same start point on X and Y does not bother me too much. The big problem is that the print is starting higher on the Z axis. So, is ruining everything.


  • administrators

    The reason it is starting too high is that you are not homing the Z axis in resurrect-prologue.g. So the printer doesn't know the Z axis position when you power it up.



  • I did what you said but now the print head is crashing into the print.

    But let's say I print a full surface volume cube and power drops. How the Z axis will home then? In this case I can home the Z only if I have the microswitch at the max end?

    And the second thing. My ressurect.g file is saved automatically on sys/ folder. How can i make to be saved in macro directory so I can resume the print from PanelDue? I can't access my sys/ folder from LCD.



  • Do NOT run Z-Homing - it will crash your print head into the bed!

    I think what dc42 meant was to undo the "G1 Z3 F3000" move from your sys/powerfail.g.
    You need something like "G1 Z-3 F3000" in sys/powerrestore.g - similar with retraction and extrusion (E4 & E-4).

    @dc42: I think repositioning Z is missing from the examples given in https://duet3d.com/wiki/Setting_up_to_resume_a_print_after_a_power_failure
    Not sure if a G91 is required before the regular G-code can run again?



  • My luck was that the print head did not crashed into the bed, only into the print. Ok, I'm making some changings and I'll keep you posted.


  • administrators

    If you read the wiki page that I wrote on this subject, you should have seen this in the Limitations section at the start:

    You must be able to re-home the printer (possibly using a different homing sequence from normal) with a print on the bed.


  • administrators

    @resam:

    @dc42: I think repositioning Z is missing from the examples given in https://duet3d.com/wiki/Setting_up_to_resume_a_print_after_a_power_failure
    Not sure if a G91 is required before the regular G-code can run again?

    Repositioning Z happens automatically, it's part of the code written to resurrect-prologue.g.

    You do not need a G90 or G91 code at the end of the resurrect-prologue.g file because absolute/relative status is restored at the end of executing any macro file to the value it had at the start.



  • During the tests, I shut down and turn on the printer. So the thing is that the printer does not manage to run the line: G1 Z3 F3000. because I don't have capacitors or something else. So the print head is sitiing on the print untill I run the ressurect.g file. I have inserted G1 Z-3 F3000 into my sys/powerrestore.g file but still the head is starting way above the print and opens my
    appetite for spaghetti.



  • @dc42:

    If you read the wiki page that I wrote on this subject, you should have seen this in the Limitations section at the start:

    You must be able to re-home the printer (possibly using a different homing sequence from normal) with a print on the bed.

    Yes, I have read it. So then I think i must implement the stall detection and home my Z by hitting the axis at the high end. Maybe on the future will be a solution for homing only the X and Y. But as I said, even if I home my Z, the print head is now hitting the print.


  • administrators

    Whether the G1 Z3 command gets completed or not doesn't affect the restore position, because the restore parameters written to resurrect.g are the position before that command is executed. The last few lines of the resurrect.g file that you quoted in your first post are:

    M23 cilindru5.gcode
    M26 S48738 P0.000
    G0 F6000 Z5.771
    G0 F6000 X76.79 Y103.62
    G0 F6000 Z3.771
    G1 F6000.0 P0
    M24

    You can see that the head is commanded up to 5.771mm, then to the correct XY position, then to 3.771mm which will be the height of the nozzle when the print was interrupted. It sounds to me exactly as if the printer has not been Z-homed when those commands are executed. On a Cartesian printer, the firmware sets the initial position to X0 Y0 Z0. So if you didn't home it, then if it stopped at Z3.771 and didn't manage to execute any of the G1 Z3 move when you powered off, it will be 3.771mm too high when the print is resumed.

    If your Z axis can't move at 6000mm/sec (which is not uncommon), check that your M203 Z parameter is set to a lower speed that it can handle.



  • In my config.g I have M203 Z1250. If I set it to 6000 It will be horrible for my Z axis. Alot of skipping steps. But is not even trying to do something because I see it does not have energy when power outage happens. Another thing I have observed is that after the G28 command, the Z axis is rising by 5mm because this is my homez.g gcode and after the print fans are starting, Z is going up at the exact height where it should start printing, X and Y goes to their position and then i don't know why, something is telling to the printer to go down on Z by i don't know how much (maybe 3mm). The head is not hitting the bed, only the print.



  • I did one more test and I have filmed everything. So the last position of Z axis when I shut down the printer was 8.51mm. After I turn it on, the printer did G28 and sat at X0 Y0 Z5. After the print fan turned on, Z got to 10.62, X and Y to the last position and then Z droped to 8.63. The last part of ressurect.g is this:

    M23 cilindru5.gcode
    M26 S109990 P0.000
    G0 F6000 Z11.226
    G0 F6000 X102.91 Y76.74
    G0 F6000 Z9.226
    G1 F6000.0 P0
    M24

    So 8.63-8.51= 0.12 This means Z should be up by about half of the layer height( I'm printing at 0.2). this is what values says but what I see is basically the head crushing into the object. Clearly, My Z is not with 0.12mm above the print.


  • administrators

    M203 Z1250 is fine if that's a speed that your Z axis can do.

    The head should go down by exactly 2mm after it moves to the correct XY position, that's what the code in resurrect.g commands.


  • administrators

    What Z homing mechanisms are you using in homeall.g and in resurrect-prologue.g; and how are you ensuring that the Z height after homing in resurrect.g is exactly right?



  • This is my homeall.g

    ; homeall.g
    ; called to home all axes
    ;
    ; generated by RepRapFirmware Configuration Tool on Sat Oct 28 2017 12:36:25 GMT+0300 (GTB Daylight Time)

    ; Relative positioning
    G91

    ; Lift Z
    G1 Z5 F6000

    ; Course home X or Y
    G1 X-205 Y-205 F6000 S1
    ; Course home X
    G1 X-205 S1
    ; Course home Y
    G1 Y-205 S1

    ; Move away from the endstops
    G1 X5 Y5 F1000

    ; Fine home X
    G1 X-205 F360 S1
    ; Fine home Y
    G1 Y-205 S1

    ; Move Z down until the switch triggers
    G1 Z-255 F1000 S1

    ; 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

    Ressurect-prologue.g is:

    ;resurrect-prologue.g

    M116
    G28
    ;M83
    ;G1 E2 F3600

    "how are you ensuring that the Z height after homing in resurrect.g is exactly right?"
    I have filmed with my phone the web page to see where my last position of the Z axis was before turning off the printer and also I have filmed where my Z axis is going after running ressurect.g file. And I have compared this values with those from ressurect.g file.

    You said something interesting and now I see. Yes, the ressurect.g file is telling to the printer to go down by 2mm. How can i make to not do this. I'm gonna do something. I'm gonna run again the experiment but before to upload the ressurect.g file I'll modify it in order to make Z to stay at the same height.


  • administrators

    The resurrect.g file tells the printer to go initially to 2mm higher than where the print was interrupted. That's why it goes down 2mm at the end.



  • Yeah I know but it's like is not respecting this. Another huge problem that I have is that after X Y Z are positioned, the extruder is trying to extrude a huge amount of filament at a huge speed. The filament is getting grinded and that's all. Hmm, I really don't know where should I start with everything



  • The extruder thing sounds like you are mixing absolute vs. relative extruder moves: M82 and M83.



  • @resam:

    The extruder thing sounds like you are mixing absolute vs. relative extruder moves: M82 and M83.

    i have M83 everywhere… Is power recover working for you?



  • What slicer are you using? Cura defaults to absolute extruder moves - but you are using relative in your code.


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