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Solved Supports breaking during print

Discussion in 'Troubleshooting' started by 4sfaloth, May 12, 2020.

  1. 4sfaloth

    4sfaloth Member

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    Hi everyone,

    I continue my saga of ever-improving print quality and reliability of my R1+.

    The issue I'm currently trying to address is that when printing miniatures with tall and narrow supports they often break mid-print, sometimes rendering the whole print useless. I have attached an image illustrating one such case.

    The issue is more frequeny when I try to print several miniatures at the same time. Sometimes the support comes loose from the build plate (mid print, not in the beginning), sometimes it actually snaps in the middle. From visual inspection I can see that while it is printing, when it moves from the support to somewhere else (ie: when it is moving to the next miniature in the same print) the small ammount of drag between the nozzle and the support is enough to make vibrate a little bit. This gets more and more serious as the support gets taller. I suppose eventually the torque is enough to set it loose from the table or break it

    I've tried reducing the travel speed down to 50mm/s, but it didn't help.
    I am now considering trying the "Enable Acceleration" and "Enable Jerk" parameters (in CURA- https://support.ultimaker.com/hc/en-us/articles/360012611079-Speed-settings), and also perhaps the "Z-Hop".
    I am in the right track? Is there anything else you'd recommend?

    Thanks in advance,
    Filipe Morais
     

    Attached Files:

  2. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    I adjusted the acceleration and jerk parameters from the default of "stupid" in the R1 firmware to "sane"
    You can do those same sort of settings in the startup GCode for most slicers, but I just did it in the firmware -- permanent then.

    If that does not solve it then you are getting overshoot on the printing which may be minor, but is enough to trash the fine-detail supports. Loose belt, loose bearing, pretty much anything that would contribute "slop" to the positioning.

    If it happens more often with multiple models then the acceleration and jerk are more likely to blame.

    The default values of them (from the Robo firmware) via Configuration.h:

    #define DEFAULT_MAX_ACCELERATION {9000,9000,100,10000} // X, Y, Z, E maximum start speed for accelerated moves. E default values are good for Skeinforge 40+, for older versions raise them a lot.

    they are in this order: (X, Y, Z, Extruder)

    9000 is dumb. Simply dumb for a belt-driven machine. Z moves very slowly with respect to the other axis so 100 is fine. The GregsWade extruder is fine since it can't possibly get up to enough speed too quickly (the gearing will eliminate and judder from that number).

    #define DEFAULT_MAX_ACCELERATION {500,500,100,10000}

    are far more sane. Jerk is the derivative of acceleration and probably should be 10 or less:

    #define DEFAULT_XYJERK 17.0

    That is the stock number.

    Now, the down side to adjusting these is that larger, more complex models will take a bit longer. Worth it if they don't look bad :)
     
  3. 4sfaloth

    4sfaloth Member

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    thank you Mark. I am glad to hear that the default max acceleration/jerks are too high; that means this might actually work ^^

    I don't really feel comfortable messing with the firmware though. I think I'll try limiting it through the slicer; I'll try to find the equivalent parameters. Are there any units for those DEFAULT_MAX_ACCELERATION and DEFAULT_XYJERK, so that I can convert them if needed?

    What about the Z-Hop? Do you think that's worth a shot as well, or a bad idea?
     
  4. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    Jerk is in mm/sec (a derivative of acceleration)
    Acceleration is mm/s^2

    Jerk is the instantaneous change in velocity, Acceleration is the rate at which it changes velocity between the Jerk setting and the requested velocity. Velocity, Acceleration and jerk :) Break out your calculus
     
  5. 4sfaloth

    4sfaloth Member

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    thank you mark. I'll try to give this a shot over the weekend
     
    mark tomlinson likes this.
  6. Henradrie

    Henradrie New Member

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    I had some success messing with tower settings in cura. Mostly making the base of towers wider. This made the supports wider and less likely to break.

    Sent from my SM-G960W using Tapatalk
     
  7. 4sfaloth

    4sfaloth Member

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    that also makes sense I guess. I'll try that out if the acceleration/jerk control do not work. Thanks!
     

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