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I have an Ender 3 Pro and I am trying to print a fairly delicate model of a low-polygon chicken as a Christmas ornament.

chicken ornament model

My slicer is Cura 4.11.0. I have successfully printed a dozen of them with 0.2 mm layer height but the legs break off super easily. As soon as I increase the quality to 0.16 mm and/or change the wall thickness to 5 (to cause complete infill in the legs) the extruder crashes into the print about 80 % through, every time (n=6). I tried changing these settings (while also troubleshooting globbing/stringing):

  • Combing Mode: noskin to infill
  • Z Hop When Retracted: False to True
  • Max Comb Distance With No Retract: 30 to 10.0 mm per this post
  • Build Plate Adhesion Type: skirt to brim (less resistant to falling over)
  • Printing Temperature: 200 to 190 °C
  • Print Speed: 50 to 30 mm/s
  • Outer Wall Wipe Distance: 0.0 to 0.1 mm

I've tried three materials, all 1.75 mm PLA:

  • 325(1000G) Silk silver blue 111932
  • Silk 335M(1KG) Silver 111858
  • Eryone Marble

The first two generic materials are pretty crap. The gooping and stringing didn't occur nearly as much with the Eryone Marble. But that issue aside, the extruder keeps crashing into the print. The brim and increased wall thickness resist the collisions but eventually, the force is great enough that the print breaks:

print failure

Resources:

I'm just not sure what else to do. I've never had this issue before on any other model I've printed. I used a level to ensure the bed is flat. I'm using a glass bed with great adhesion (clearly; the model breaks before it comes off the bed.) Instead of the Z-stop, I'm using the BLTouch, which samples 16 points before every print.

I thought that maybe moisture trapped in the material might be slightly increasing layer height with each layer, causing the print to fail after the same number of layers each time late in the print with a low layer height, but succeeding with a higher layer height. However, the ambient air temperature is 17 °C and the relative humidity is 44 %, not particularly high. Furthermore, different materials of different ages stored in the same location have the same failure. I don't have a dehydrator to be totally sure, though. I've been wanting to build one so this may be a good excuse. But any other advice or suggestions would be immensely appreciated!

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  • $\begingroup$ What's your nozzle diameter and fill density? +two things to check: 1) Keep 0.2 mm layers and increase wall thickness to 5, set infill pattern to "Concentric", you can also reduce fill density (looks like legs break because of the weight of layers on top) 2) Try better material - PLA plastic is not the strongest one. One of the best suitable for your printer is a mix of PC and ABS plastic. PC is even stronger, but your printer may not support temperature necessary to print it. Pure ABS can also work well. $\endgroup$
    – Stepan Novikov
    Dec 29, 2021 at 10:58
  • $\begingroup$ Thanks @StepanNovikov. I am using 0.4mm nozzle with 20% infill density. I did try 0.2mm layers with wall thickness to 5, but I did not try any different infill patterns. Why concentric? Regarding other materials, I've never tried anything other than PLA! I have half a mind to try other materials soon. $\endgroup$
    – Micah Henning
    Dec 29, 2021 at 22:33
  • $\begingroup$ I was trying concentric in print with legs and it was a bit more durable than with rectilinear in such places with 100% infill in my experience, however, in general a print would be less strong, especially in places without 100% infill. As I understand, this adds a bit of elasticity even for rigid plastics like ABS, let alone PLA, so to some extent thin concentric shapes like legs would bend instead of break. Anyway, IMHO using plastic with a bit better mechanical qualities like ABS or ABS+PC would give better effect than such tricks. $\endgroup$
    – Stepan Novikov
    Dec 30, 2021 at 12:31
  • $\begingroup$ Do you know if its the nozzle or the bl touch that hits the part ? Given the last layer is the widest so-far, I wonder if the levelling sensor is mounted low enough to catch it ? $\endgroup$
    – Criggie
    Jan 1, 2022 at 5:08
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    $\begingroup$ @Criggie Thanks for the reply! It is the nozzle that crashes into the print. The BLTouch sensor in closed position is at least a couple centimeters above the nozzle hot end. $\endgroup$
    – Micah Henning
    Jan 3, 2022 at 21:37

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