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Unresolved Wobbly Ghost problems

Discussion in 'Troubleshooting' started by athlonduke, Sep 14, 2018.

  1. athlonduke

    athlonduke New Member

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    Hi there, has anyone managed to make this guy thingiverse.com/thing:1064239 *with* a working spring? that damn thing is driving me crazy, I've done 5 of them now and while the outside is good, that spring is horrible. as the head tries to print the layer, it is just extruding into thin air and causing a mess, the only "structure" to the spring is the small section that overlaps between layers.

    I also can't seem to print it faster than about 20mm/s, overhangs and shadowing are bad if I do otherwise. i'm pretty sure that's acceleration settings though. gcode doesn't help, I think I need to flash it but i'm not sure how to do that and i'm too lazy at this point (slow is fine)

    repetier for slicing, feeding it to octopi for printing. 200 micron for quality setting. that's wood PLA, I had the same issues with two different GITD PLA. 190 head and 60c bed
     

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    #1 athlonduke, Sep 14, 2018
    Last edited: Sep 14, 2018
  2. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    I have printed similar before, but not that exact one.
    This is going to be a stress test of how well you have the printer calibrated.
    Any over extrusion or heat issues (too hot for example) will be greatly exacerbated because there is little room for error.

    Start with a temperature tower and test to find your best extrusion temperature for that filament (with practice something small and quick like a dePrime test object is enough to dial it in). Different printers print filament different filaments at different sweet spots. All spools require testing on every printer (at least a bit of testing). I have 2 identical printers and one will print most PLA best at 195c, the other at 175c. They sit a few feet apart so environment is not the difference either. Even then some spools are different (so I mark them up to help me remember)

    Another thing to do is to slow down the print speed. Start by cutting it in half and then play with it from there. Too much acceleration and jerk can make a mess on fine details.
     
  3. athlonduke

    athlonduke New Member

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    I don't think I can slow it down much more, 20mm/s is pretty damn low. i'll try at 180 tonight and verify the speed settings.
     
  4. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    Not as slow as I do Flexibles :)

    Yes, you are probably slow enough but make sure acceleration is reduced -- the stock numbers were just stupid and that affects direction changes (which your model has "several" of)
     
  5. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    For example these are the stock firmware settings for acceleration on the R1+:

    #define DEFAULT_MAX_ACCELERATION {9000,9000,100,10000} // X, Y, Z, E maximum start speed for accelerated moves.

    For extruder that is fine, for Z that is fine, for X and Y? Nope. Those are not 'fine' they are in fact 'dumb'

    // The speed change that does not require acceleration (i.e. the software might assume it can be done instantaneously)
    #define DEFAULT_XYJERK 17.0 // (mm/sec)

    This is also a little high.

    "jerk" is the rate of change of its acceleration with respect to time. So think of as jerk the time derivative of acceleration, and as such it is the second derivative of velocity, or the third time derivative of position. :) Not that anyone cares but 'snap' is the fourth derivative of displacement with respect to time ;) Just to be complete. Velocity->acceleration->jerk->snap
     
  6. athlonduke

    athlonduke New Member

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    that's what I've read on other posts, I just haven't bothered to figure how to flash the firmware. instead I've stuck this in my GCODE startup :

    ; Default start code
    G1 Z5 F5000 ; lift Z by 5mm
    G28 ; home all axes
    M565 Z-.8; set the offset for auto-leveling mechanism
    M201 X1000 Y1000 Z100 E2000
    G29 ; run auto-level
    M300 S440 P200 ;A4: 440
    G0 Z5
    G1 Z5 F{Z_TRAVEL_SPEED}
    M107 ; Turn off fan
    G90 ; Absolute positioning
    M82 ; Extruder in absolute mode
    {IF_BED}M190 S{BED}
    ; Activate all used extruder
    {IF_EXT0}M104 T0 S{TEMP0}
    G92 E0 ; Reset extruder position
    ; Wait for all used extruders to reach temperature
    {IF_EXT0}M109 T0 S{TEMP0}
     
  7. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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  8. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    Once you get it to where it is happy then flash it :)
     
  9. athlonduke

    athlonduke New Member

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    question: does the printer have some kind of cut off at less than 190C on the head? I set it for 180 and the feed motor doesn't turn anymore. bump the temp to 190 and it starts back up.
     
  10. athlonduke

    athlonduke New Member

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    getting there! 190 head, also upped the retraction speed from 40mm/s to 140mm/s based on some other posts here. lastly, I told octopi to reduce the feed rate to 80%.
     

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  11. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    Some versions of the firmware have the min temp cutoff set to 185c if I recall correctly. You should have a message in the GCode terminal about that in that case.
     
  12. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    You can adjust this in the firmware yourself if you like, I have one that needs to print PLA at 175c :)
    Thermistor accuracy and filament and environment differences add up.
     

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