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Answered PLA Shrinking Inward on Circular Perimeters

Discussion in 'Troubleshooting' started by Corey Harris, Oct 1, 2018.

  1. Corey Harris

    Corey Harris New Member

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    I've been trying to troubleshoot what I believe is a PLA cooling issue today with no luck. The first half inch or so of a cylindrical print that I have continuously shrinks inward, and I have not been able to get consistently straight sides despite my troubleshooting. To me, it seems to be that area is cooling too fast and retracting too much. I've tried different combinations of lowering the print speed, increasing the minimum layer time, decreasing the temperature, lowering the print cooling fan for more initial layers. I'm currently printing at 0.15 or 0.2mm with a 20% infill. I've attach a couple photos of the issue. IMG_20181001_091357.jpg IMG_20181001_083818.jpg
     
    #1 Corey Harris, Oct 1, 2018
  2. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    #2 mark tomlinson, Oct 1, 2018
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  3. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    % infill will also affect shrinkage as will print temperature. I always try to minimize heat issues by printing as cool as I can (only as hot as needed) for any given filament*. This takes a bit of experimentation. I then note the temperature for that spool and printer.






    *true for all FDM filaments
     
    #3 mark tomlinson, Oct 1, 2018
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  4. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    #4 mark tomlinson, Oct 1, 2018
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  5. Corey Harris

    Corey Harris New Member

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    Fantastic! Thank you for your help! I think I may still be printing too hot, and could stand to increase my infill percentage as well. Gonna run through the calibration again to see if I can find the issue. Thanks again!
     
    #5 Corey Harris, Oct 1, 2018
  6. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    :)

    Good luck and if you run into questions fire them over.
    In general you will get a feel for how much filaments shrink (or a few odd ones that swell) and then adjust your modeling to suit.
    Trust me you can get to the point where you can model details like finely messed moving parts that will, in fact, actually move interlocked when printed.
     
    #6 mark tomlinson, Oct 1, 2018
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  7. Corey Harris

    Corey Harris New Member

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    So I calibrated the extruder and got it within just 1 or 2 mm of extruding exactly 100mm, so I tried the print again a few more times, and got the same result each time. I tried one with increased flow rate, and one with a lower print temperature, and didn't see much improvements. I'm going to try a higher infill as well, but wanted to go ahead and report back.
     
    #7 Corey Harris, Oct 3, 2018
  8. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    Well, there is always the chance that it is just the model or that it is just that filament so try swapping to a different filament as well.
    Make sure the side really are straight on the model and run it through a tool to make corrections for printing as a check there as well (something like NetFab's repair -- another link here --- or the Simplify3D repair tools)
     
    #8 mark tomlinson, Oct 3, 2018
  9. Corey Harris

    Corey Harris New Member

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    Yeah, I can confirm that it's straight. I created it Fusion360 using a revolve from a rectangle. I think I may have fixed it though. I reduced the bed temp by 10 degrees and print temp by 5, and increased the infill. It seems to be printing much better now.
     
    #9 Corey Harris, Oct 3, 2018
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  10. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    Best approach to resolving heat issues (or potential heat issues) is to try less :)
     
    #10 mark tomlinson, Oct 3, 2018
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  11. S1hane

    S1hane New Member

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    Have you tried a big ol' fan? I did the dual 40mm black widow fans on my R1+ and it really helped with my PLA prints
     
    #11 S1hane, Oct 7, 2018

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