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I printed the following object (I'm printing the single opening version, Flower_pot_3.STL), and observed an unusual print artifact. I would like some idea of what's going on so I can avoid it in the future. The object is essentially an open-top box. In the image below, you can see a ridge along the bottom of the print. This corresponds to the upper surface of the bottom side of the box. The ridge is present for 4 layers, the same number of layers on the top surface. The defect is basically a positive ridge all the way around (not a layer shift). The G-code render below is for the top layer of the bottom surface.

System Settings

  • Printer is Prusa Mk3, with white PLA plastic. Nozzle is HS steel at 210 °C
  • 0.2 mm Layer height, 15 % Gyroid infill, 3 perimeters
  • Perimeters are printed first each layer, with the outer perimeter coming last.
  • -

Image attempting to highlight flaw

G-code preview of top layer of the bottom surface of the print

Ideally, I would like to know what caused this artifact, and what I could do to avoid it in the future. I can add more information as requested.

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    $\begingroup$ This is frequently seen when prints transition from one shape to another (filled cube to empty cube). You normally see this happen at cheaper or less accurate printers, this can be backlash or plain accuracy of the machine. CoreXY printers don't show this, Prusa models/clone are more susceptible for such defects. Maybe you could point out what the order of printing is of the layer; e.g. first infill or first walls, which walls, when is the inner bottom surface printed, etc. Is the ridge at the top of the bottom surface, or starts at the first layer of the inner bottom surface $\endgroup$ – 0scar Apr 5 '19 at 9:30
  • $\begingroup$ Do you print Walls before infil or infill before wallsl? that can sometimes result in such behavior. $\endgroup$ – Trish Apr 5 '19 at 9:50
  • $\begingroup$ I've added the information. What's puzzling to me is that the solid fill is so far away from the perimeter, and the perimeter drawing is almost identical to the previous layer. $\endgroup$ – W5VO Apr 5 '19 at 13:46
  • $\begingroup$ At least w/ my Cura defaults, certainly no change in the physical model parameters, and layers 249, 250, 251 (where first layer of solid region shows up) appear to have same gcode operating values $\endgroup$ – Carl Witthoft Apr 5 '19 at 15:04
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    $\begingroup$ Did you figure this out? I am having the same problem but unsure why it is at the moment. $\endgroup$ – Stephen Mottershead Apr 3 at 14:10
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Just a guess here. If I understood correctly the deformation is at the first layer of the box bottom, it seems highly unlikely that it randomly happened at this exact position so I am assuming that if you do the print again you will get the same deformation at the same place (you can test this maybe ? I know it is a long print). In this case it is more likely that is a slicer issue than something with your machine and it could also be a problem with the stl model. Maybe try to create a small simple box then slice it using the same setting and try to see if you can reproduce artifact.

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    $\begingroup$ You've "hidden" two different possible slicer errors. The first is an actual change in the object shape, which should be visible in LayerView. The second is a change in gcode instructions as to movement speed, extrusion rate, and so on. Those would be useful to check out. $\endgroup$ – Carl Witthoft Apr 5 '19 at 14:55

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