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I am currently printing a simple cup out of PLA (I will later anneal it). My nozzle is 0.8 mm and I'm using a 0.4 mm layer height. Unfortunately, the layers keep separating. They don't detach completely, but there are 1 layer-tall, 3-7 mm wide gaps. I increased the temperature, since my speed is 100 mm/s. I also tried decreasing cooling and increasing the flow. This only helped a little bit.

Moreover, small increases in the temperature like 230/240 °C didn't work and now I have to use 270 and even 280 °C, which is crazy, considering my layer height is 0.4 mm. Is there any easy solution that will increase the quality?

Settings:

  • Material: PLA
  • Layer height: 0.4 mm
  • Nozzle: 235 °C first layer, 270 °C for the rest.
  • Bed: 60 °C
  • Cooling: 62 %
  • Speed: 100 mm/s

I have noticed that 280 °C is better for large prints (large area, not height) and small prints look better when I change the temperature to 240/250 °C. This is how my prints look by now. The extrusion is very inconsistent, with overextrusion in the middle of the layers and gaps in the corners:

enter image description here

enter image description here

I suspect that the layer lines are not parallel to the heatbed and are over extruded, because of the high temp. I lowered it to 230 °C and there was no drooping/over extrusion, but there were more 'holes'.

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    $\begingroup$ Is it possible that your hotend cannot keep up with the flow? Hence the large temperature? $\endgroup$ – 0scar♦ Apr 14 '20 at 19:21
  • $\begingroup$ The hotend is the default one that comes with Prusa MK3S. I don't know how powerful it is and I don't know how to check if that's the case. My flow is around 100 now. $\endgroup$ – StLuke5 Apr 14 '20 at 19:31
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    $\begingroup$ Just for troubleshooting, have you tried printing more slowly? $\endgroup$ – Aerik Apr 14 '20 at 19:48
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    $\begingroup$ Wow, that is smoking hot for PLA ... $\endgroup$ – Pᴀᴜʟsᴛᴇʀ2 Apr 14 '20 at 19:53
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    $\begingroup$ Large nozzles can make larger heights but need to be done slower unless you have a more powerful heater or longer meltzone. $\endgroup$ – Trish Apr 15 '20 at 9:29
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After printing ~30 calibration test cubes I finally figured out the perfect settings.

  • Apparently, the extrusion width in my slicer was set to a certain number, instead of percentage. I was printing at 0.45 mm extrusion width, which was ~105 % of the 0.4 mm nozzle diameter, but less than 50 % of the 0.8 mm one. Changing the value to 130-140 % solved the majority of my printing problems.
  • As I predicted, the 230-280 ℃ nozzle temp. was ridiculously high, even with the 0.8 mm nozzle. I gradually lowered it to 210 ℃ (ironically, the value I chose at the very beginning).
  • There was some warping, so I cleaned the heatbed from the glue, put the glue again and decreased bed temp. to 50 ℃
  • Finally, I decreased the flow from 1.3 to 1.05 and everything seems perfect now.

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      $\begingroup$ Nice that you shared your solution, this was hard to guess based on your question! This proves that stating all the print settings is a must for solving print problems. Your small extrusion width in combination with the large flow modifier mimics the wider extrusion width, but fails to do a proper job. +1 from me! Note that I still find 100 mm/s to be fast for a 0.8 mm nozzle, but of it works, go for it! $\endgroup$ – 0scar♦ Apr 16 '20 at 11:20
    • $\begingroup$ @0scar Thank you! I found that larger prints required higher temperature/different settings, but luckily the most important part is done. $\endgroup$ – StLuke5 Apr 16 '20 at 13:05

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