Lower layers quality

Discussion in 'Calibration, Help, and Troubleshooting' started by markoaurelije, Mar 24, 2017.

  1. markoaurelije

    markoaurelije Active Member

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    I'm having issues with lower layers perimeter quality.
    Usualy it's happaning when upper layer perimeter overhangs sligtly on the layer below. Like overhang, but very low angles that usualy don't cause problems, and with constant angle upper layers are perfect (beyond 3-4mm height).

    See the picture attached - found it on web just for reference. Similar issues I am experiencing o_O

    Anyone know what's the cause? Bed too hot?
     

    Attached Files:

  2. Spoon Unit

    Spoon Unit Well-Known Member

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    This is often the result of small overhangs curling up. I'm not sure if there's a magic formula to fix this is it doesn't always happen, but certainly circular objects seem to exhibit it for me more than with straight edges. I think, underneath it all, the tension of the material as it is layed pulls at previously laid material. It's ability to do so is a factor of material temperature and solidity. So, I'm guessing that printing at a cooler temperature might help or using the part cooling fan. Of course, the part cooling fan can then have the impact of cooling the bed and lowering bed adhesion, so you might want to tweak up the bed temperature a spot if you're going to try with the part fan. I'm looking forward to reading other people's thinking and logic about this as I'd love to get to the bottom of it.
     
  3. markoaurelije

    markoaurelije Active Member

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    The cooling fan is at 100%.
    The interesting thing is that at higher layers with the same part geometry this does not happen.
     
  4. Spoon Unit

    Spoon Unit Well-Known Member

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    Right, but then each layer is ontop of something, not air.
     
  5. markoaurelije

    markoaurelije Active Member

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    The image attached is just an example found on web for the similar issue happening to me.
    I don't have an image of my exact part right now...

    The part I'm having issue is linear all the way across Z. It has uniform "low" overhang angle throughout entire part. And lower section of the print comes out rough, but the rest is super fine. That's what is confusing to me.
     
  6. markoaurelije

    markoaurelije Active Member

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    Here a timelapse of similar issue I'm having at lower layers.
    Take a look at what's happening with left part's support structure at low layers, and then out of the sudden things gets better. :(

    colorfab PLA
    63°C bed / 195°C nozzle
    fan incrementaly to 100% after 1st layer (full on at layer 10 - 100% does not seem to help much to reduce issues)

     
    #6 markoaurelije, Mar 24, 2017
    Last edited: Mar 24, 2017
  7. Ephemeris

    Ephemeris Well-Known Member

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    I've seen this. It can be particularly bad with vases with an overhang near the bed. The boundary layer of air right above the bed can be quite hot. This slows cooling and allows the print to slump. The solution for me is to turn on the cooling fan for layer two and keep it on for the first few millimeters.
     
  8. Spoon Unit

    Spoon Unit Well-Known Member

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    I'm wondering if printing at a colder temp might also help.
     
  9. markoaurelije

    markoaurelije Active Member

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