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I just switched to the Duet Wifi board (used MKS Gen L 1.0 before) and now small structures look terrible. From my observations the hot end moves correctly, but almost no filament gets extruded. On the other hand larger structures look very good. With the MKS board the exact same G-code worked fine. After that I gradually disabled many features like coasting, wiping and even retractions altogether, the quality only improved by a tiny margin.

Example print (the two towers should be cylinders): Example print

Additional information:

  • Printer: JGAurora A5
  • Material: PETG
  • Slicer: Simplify3D

More info (edit):

  • Hot end temperature: 225 °C (for the affected layers)
  • Bed temperature: 60 °C (I corrected the thermistor data, it's equivalent to 70-75 °C on other JGAurora A5 printers)
  • Nozzle diameter: 0.4 mm
  • Part cooling fan: 100% (improved cooler duct by Da Hai Zhu)
  • Print speed: 50 mm/s (50% for outline)
  • The cylinder is printed hollow because of my infill settings
  • Lubricant is fresh, belts are tightened, so there should be no mechanical issues
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  • $\begingroup$ Welcome to 3DPrinting.SE! Could you edit your question and put the rest of the parameters in there, such as heat block temp, bed temp, cooling, etc. The more information, the better. $\endgroup$ – Pᴀᴜʟsᴛᴇʀ2 Jan 12 '19 at 23:26
  • $\begingroup$ Your print looks as if it was printed way higher than 225 ℃, furthermore PETG doesn't need 100% cooling, but that is not your problem here. Is the right thermistor type chosen in the firmware? $\endgroup$ – 0scar Jan 13 '19 at 6:04
  • $\begingroup$ @0scar Well I basically took the temperature table from my previous firmware (jgaurorawiki.com/a5/firmware), which was measured by someone else (worked fine with the MKS), and reverse calculated 3 entries. Then I used a thermistor calculator to get the beta-value for the Duet. Is this too unprecise? Measuring the actual hot end temperature is a bit difficult for me because I can not properly attach a thermocouple without burning the attachment of. $\endgroup$ – dav20011 Jan 13 '19 at 8:30
  • $\begingroup$ @0scar I just found about the method of removing the nozzle and then inserting the thermocouple. The actual temperature is 10°C lower. $\endgroup$ – dav20011 Jan 13 '19 at 11:30
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    $\begingroup$ To complete this, the issue was related to the part cooling fan not spinning correctly. After replacing it the problem was gone. $\endgroup$ – dav20011 Apr 16 '19 at 23:18
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The OP found the solution and shared this in comments but has not written a proper answer. The OP found:

To complete this, the issue was related to the part cooling fan not spinning correctly. After replacing it the problem was gone.

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This actually just looks like heating issues. Cura has an option to set a minimum layer time and speed, and any layer that takes less than that amount of time it'll lift the head away from the print to allow the plastic to cool.

Unfortunately, the only things I can find for Simplify3D around head lift and minimum layer times are software feature request posts from 2017, or some features around scaling print speed for small layers, but unfortunately that'll just print the same object much slower and may not properly allow the part to cool as the melting-temperature print head is still sitting directly on top of the part.

I hate to be someone to suggest a software change, but you might try using Cura and seeing if you get better results with features such as this.

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    $\begingroup$ Scaling print speed is usually superior to the lift-and-wait method. My experience with lift-and-wait is some filament will seep from the nozzle during the wait time, creating a problem when printing resumes. $\endgroup$ – Joel Coehoorn Jun 3 '19 at 15:44
  • $\begingroup$ This question has an answer by the OP in comments, please unfold all comments under the question to see them all. @Greenonline could you convert the comment of the OP to an answer? $\endgroup$ – 0scar Jun 3 '19 at 16:05
  • $\begingroup$ ah I hadn't seen that. Upboated the comment in question. @JoelCoehoorn, I've had the issue you're describing but for very small parts I found the little tags were easier to dispose of than dealing with the feature collapsing due to radiant heat from the block. $\endgroup$ – Nach0z Jun 3 '19 at 16:23

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