Benchy - Why so many problems? ...

Discussion in 'Calibration, Help, and Troubleshooting' started by Mark_T, Jun 4, 2016.

  1. Mark_T

    Mark_T Well-Known Member

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    Just a passing thought, but reading all the posts about printing the supplied benchy, the consensus seems to be that as supplied, it is almost impossible to print properly and there is a need to intervene to adjust the fans to avoid thermal runaway.

    So perhaps I just don't understand the problem, but why wouldn't E3D produce a file that is printable with the BB?

    Seems like it is pretty pointless to keep giving people an unprintable file as a tool for testing their newly assembled printer... ?
     
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  2. Greg Holloway

    Greg Holloway Administrator
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    It's usually because the print-cooling fan is not correctly positioned. This means air is directed straight at the nozzle instead of below and away from it causing the nozzle to cool and trip thermal runaway protection.

    The fix is to preposition the fan correctly.

    The hack is to unplug the fan or re-slice the benchy and reduce the fan speed so it makes the problem appear to go away.
     
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  3. Mark_T

    Mark_T Well-Known Member

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    Seems like many people are doing it wrong then as I'm seeing a lot of advice to micro-manage the fan settings instead of re-positioning the fan.

    Thanks for the input, I'll pay close attention to the fan position when I get my chance to build ...
     
  4. orcinus

    orcinus Well-Known Member

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    Finished my build's commissioning and configuration today, printed the supplied Benchy, absolutely zero issues with thermal runaway.
    Haven't touched the fan controls.

    I did, however, notice the side facing the fan is very saggy, unlike the side facing away from it, which would indicate my fan might be a bit lower than it probably should be. I think. Maybe. Possibly.
     
  5. Alex9779

    Alex9779 Moderator
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    The problem is to provide a file that will work for all the possibilities how you setup the box.
    This is no Ultimaker 2 where everything is "dialed in" because you have no real possibilites to adjust something.
    I myself had problems at first getting the homing and moving to the dock right. My head crashed in the back of the IR sensor hung at the ooze wiper. The tolerances are quite low, only a few millimeters, and so is the fans positioning which is essential to get no thermal issues.

    Also the file can be only for one specific material, what if you didn't order any PLA? Then the provided file is useless for you...
     
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  6. Greg Holloway

    Greg Holloway Administrator
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    There is a new set of pre-sliced g-code on the way which incorporates the reddit competition winning models. I just need to find the time to do it....
     
  7. Mark_T

    Mark_T Well-Known Member

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    While one might wish that the design of the parts made it easier to get the fan location correct first time, it is actually helpful to know that if the supplied benchy doesn't print then something is wrong, rather than the advice that seems to be given so often to just change the fan settings on the fly. Clearly a little tinkering needed to get it all correct, but happy to tinker now I know the file itself is not flawed :)
     
  8. Old_Tafr

    Old_Tafr Well-Known Member

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    It is (unfortunately in some ways) possible for the benchy to print with the fans too high. This leads you into a false sense of security/confidence, only to find that your first real print fails with a Thermal Runaway. This is exactly what happened with me; Benchy worked first time, built and commissioned the printer exactly by the Build WiKi, original firmware plus Pi, Pi camera and OctoPrint etc......... loaded filament, did the 100 mm calibration, ran the Benchy gcode file from the SD card, everything standard on a BB 1.0 dual.

    I suspect that other factors, a grub screw not tight, a belt too tight or a million other things including environmental factors. ambient temperature different, maybe even using some other filament not the supplied samples from e3d, means that the Bency print fails.

    But, my first real prints failed with Thermal Runaway (TR) However once I set the print cooling fans between 1.5 and 2 mm and set the fans at zero for the first few layers then building up to 60% (max) from layer 6 onward then PLA worked fine.

    First prints, be sure to use the manufacturer's recommendations for both nozzle and bed and not the defaults in either OctoPrint or s3d.

    PLA (Cough :confused: ABS :) ) needed zero print cooling fans. 245 nozzle, 110 for bed.

    These are settings both fans and temperatures that work for me, they may not work for everyone.
     
    #8 Old_Tafr, Jun 5, 2016
    Last edited: Jun 5, 2016
  9. Alex9779

    Alex9779 Moderator
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    Sounds more like ABS...
     
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  10. orcinus

    orcinus Well-Known Member

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    ^ Yup, that sounds pretty much like ABS.
     
  11. orcinus

    orcinus Well-Known Member

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    Here's the Benchy as it came out from my BigBox:

    [​IMG]

    [​IMG]

    [​IMG]

    That was literally the first print after finalizing assembly, flashing and commissioning.
    Apart from Mesh bed leveling crashing the bed into my print immediately before that (for reasons unknown - it worked fine on the next attempt), absolutely zero issues.

    The benchy was by no means perfect, there are issues with sagging on one side, the Z layers are less even than i'd like them to be, and the top surface isn't as nice as i'd like, but hey - it's a pre-cooked gcode file and i just hit print.
     
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  12. Alex9779

    Alex9779 Moderator
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    I had similar effects when changing firmwares. Seems to be a problem in Marlin, using some old values or some variables not cleared properly. No I reset the EEPROM every time I have a major firmware change (load failsafe then store settings) and power cycle the box to have a defined state...
     
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  13. orcinus

    orcinus Well-Known Member

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    Good point.
    The way it used to work, it used to store a checksum and ensured that any newly introduced EEPROM vars got a new (higher) address, so there'd be no corruption or unwanted effects after a reflash. But it's possible this has gotten buggy/unreliable over the years.
     
  14. Stian Indal Haugseth

    Stian Indal Haugseth Well-Known Member

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    Which extruder does benchy print when dual? I have a 0.8mm nozzle on E0 (left).
     
  15. orcinus

    orcinus Well-Known Member

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    The first one, whichever one that is :X
    (in your case the left one)
     
  16. Stian Indal Haugseth

    Stian Indal Haugseth Well-Known Member

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    Hmm.. OK. Need to fix the gcode to print on the other extruder.

    What nozzle size is the benchy made for?
     
  17. PsyVision

    PsyVision Moderator
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    Have a look in the g-code, at the top are all of the S3D settings used if I remember correctly.
     
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  18. hussain

    hussain Member

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    Hey mark if you keep getting thermal runaway in the future you can use kapton tape around the hot end block.
     
  19. Mark_T

    Mark_T Well-Known Member

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    I dream of getting thermal runaway as that would mean I actually had my BB instead of waiting for it to ship :)

    However, I am reassured by the fact that when setup correctly it shouldn't happen with the Benchy file so I'll work on fixing the setup rather than treating the symptoms if it happens, but thanks for the tip on the kapton tape, I'm sure it will have its uses at some point.
     

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