Issues with ABS - scarring & bridging

Discussion in 'Calibration, Help, and Troubleshooting' started by Sean, Jun 23, 2016.

  1. Sean

    Sean Member

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    Been working on calibrating the printer for the past few evenings,, and having some issues that I didn't get with my previous printer (Prusa I3)

    The outside edges of the print, especially after a certain Z-level, start to get this weird scarring - no idea what could be causing it, hopefully it comes through in the pictures. Especially noticeable on the back of the half-dome on the calibration piece (image 2)
    Also, my bridging still isn't perfect - it's definitely improved a lot since I first started, but can't seem to get it any better than what's (hopefully) shown - any advice? Shown image 3

    Bigbox dual hybrid (bowden extruder)
    Material: ABS
    Nozzle: 225
    Bed: 115

    Thanks in advance for any replies
    2016-06-23 17.44.23.jpg 2016-06-23 17.44.32.jpg 2016-06-23 17.44.38.jpg 2016-06-23 17.44.47.jpg 2016-06-23 17.44.55.jpg 2016-06-23 17.45.01.jpg
     
  2. Chase.Wichert

    Chase.Wichert Well-Known Member

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    Do you mean the globs you are getting on the outside?

    Scarring typically is referred to as a nozzle dragging over a top surface.

    Have you calibrated your ESteps? It is good to use the code provided as it doesn't feed it too fast. If you just use the LCD to extrude 100mm I believe it doesn't extrude enough. Also I print ABS at 240C. And ABS isn't particularly good with overhangs unless you use a fan, which is not recommended with ABS. But I have gotten a good benchy with abs at 240C

    You may also want to play with your retraction settings.
    Retracting 1-2mm between toolpaths can help prevent globbing or oozing at the start and stop of a line.
     
    #2 Chase.Wichert, Jun 23, 2016
    Last edited: Jun 23, 2016
  3. Sean

    Sean Member

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    @Chase.Wichert
    Yes, the globs on the outside - sorry, i don't know the correct terms.

    I've calibrated the esteps to the calibration gcode on the SD card - getting as close to 100mm as I can measure with my calipers.
    I was originally printing hotter, at 240, but lowered it at some point in the calibration process to reduce the stringing I was getting.

    Retraction is currently at 12mm - I was originally printing with 3mm retraction and got huge stringing/branches coming off the uprights on the part. Going to 12mm i've finally been able to remove them, it definitely slows the print dow, but solved the major issue I was having where pieces would look more like furry cobwebs.
     
  4. Chase.Wichert

    Chase.Wichert Well-Known Member

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    12 is way too much. You run the risk of pulling the melted filament back up into the heat sink and freezing it off in the heat sink, it will cause a clog. 1-2mm is all that is necessary.
     
  5. Chase.Wichert

    Chase.Wichert Well-Known Member

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    These are my settings.
    1.PNG
    2.PNG
     
  6. Chase.Wichert

    Chase.Wichert Well-Known Member

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    just ignore the nozzle diameter,and set it to the correct one with Automatic width
     
  7. Sean

    Sean Member

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    @Chase.Wichert
    I'll try lowering the retraction again, and raising the temperature - I'll get back to you with any results - hopefully it's a combination of these things that's causing the issues - which would explain why things were getting better with my current settings.
     
  8. R Design

    R Design Well-Known Member

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    @Chase.Wichert are you really operating at 100mm/s retraction speed or is it actually limited in firmware to something lower? By default it's limited to 25mm/s.
     
  9. Chase.Wichert

    Chase.Wichert Well-Known Member

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    I think it is limited to 25mm/s I haven't changed that in a long time
     
  10. Sean

    Sean Member

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    Temp set to 240 seems to have helped the blobbing on the outside - but it hasn't gone away completely
    Setting retraction to 2mm has brought back the branching seen in the pictures. I'm going to start bringing retraction up again unless there's a better solution to that.
    2016-06-25 09.47.48.jpg 2016-06-25 09.47.59.jpg 2016-06-25 09.48.05.jpg
     
  11. Chase.Wichert

    Chase.Wichert Well-Known Member

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    Did you try the wipe settings? And in the other menu you have to check retract while wiping or something.
     
  12. Sean

    Sean Member

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    Yes, This is with your exact wipe settings.
     
  13. Chase.Wichert

    Chase.Wichert Well-Known Member

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    And that is with a .4mm nozzle?
     
  14. Sean

    Sean Member

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    Yeah, .4mm nozzle on the e3d v6, Bowden extruder on the Dual Hybrid carriag.
    40mm/s print speed
    0.1mm layer height
    2 perimeter shells, inside/out direction
    3 top/bottom shells
    start points optimised for print speed
    print speed for layers below 15sec reduced by down to 20%
    retract between layers, during wipe and only wipe on outer perimeters
     
  15. Chase.Wichert

    Chase.Wichert Well-Known Member

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    Can you get a good video of it printing some of those sections? Like when it actually drops those globs, is it at the beginning of the perimeter or at the end of the perimeter?
     
  16. Sean

    Sean Member

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    I'll start another print with a camera pointed at it - should be about 2 hours and i'll post here with the result
     
  17. tohara

    tohara Well-Known Member

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    Are you using the bowden extruder for this testprint?
    The oozing issue and blobs looks like what I had on my previous printer with bowden, and I was never able to completely compensate for it.
     
  18. Sean

    Sean Member

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    @tohara
    Yes, I am
    My previous printer (Prusa i3) went through a couple iterations of bowden/direct, and I found more retraction was needed with bowden to compensate for the flex in the bowden tube, which is why I had higher retraction earlier.
    I've seen people get perfect prints with bowden before though, so I see no reason for it to be an unresolvable issue.
     
  19. tohara

    tohara Well-Known Member

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    @Sean
    Makes sense why you had that long retraction then. Have you tried increasing Vmax E to get quicker retract?
     
  20. Sean

    Sean Member

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    Found out what was happening - no idea how i'm supposed to resolve it, but it's a start

    During the print of the dome, when it's doing the infill - small strands of filament stick up after the nozzle has passed over - then when the nozzle goes over doing theperimiter wall for the next layer the strand sticks to the outside of the nozzle. When it gets to the edge of the piece this strand gets deposited along the edge - over a few layers this builds up, jit just so happens in the same place every time causing the weird blobbing.

    Now, any idea how I stop this happening?
     

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