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This problem has been occurring for a while. On the top of round objects, you can see the individual layers. Maybe I just need a lower layer height.

Photo of a 3D printed model with printing errors on the top

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    $\begingroup$ Please edit in additional information such as printing temps, speeds, etc. to help offer a solution. $\endgroup$
    – agarza
    Apr 10 at 12:24
  • $\begingroup$ See this answer, it describes why the top layers of dome/round shapes are rough. $\endgroup$
    – 0scar
    Apr 10 at 17:49

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At the top of curves layers will always be more visible because the layers are increasing offset from each other. Layer height will help with this, but if you really want it smooth you will need to do some post-processing.

Usually if possible I avoid having a top surface like that of any significant size. But when I do I either leave it and post process or add some little design elements to break it up a bit. So it's still there but not really noticeable.

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Kilisi is absolutely right that you necessarily (without advanced non-planar slicing techniques that aren't available in production slicers) have a "stairstep" effect whenever you have a shallow angle top surface like that. However, it looks from your picture like you also have some gaps that are accentuating the problem and making your top surface non-watertight. This can be fixed.

Slicers (at least Cura) are fairly bad about figuring out where they have to put material under the very top layer to ensure that you have a solid wall of the desired thickness. Where the outer wall face is pointing almost-upward, you would need either a lot more outer perimeters than the shell thickness you want, because they're significantly offset from each other (often by as much or more than the whole 2D wall width) at each successive layer. Using excessively many walls will solve this, but wastes a lot of print time and material. Using more top layers is the easiest fix I know. I find that 5 top layers at 0.2 layer height pretty much always gives solid curved tops, even with spherical top shape. The only way that might fail is if you have really low infill and they all "sink in" rather than bonding properly.

Of course these gaps could also be caused by underextrusion or misplaced extrusion. Check instructions for enabling and calibrating Linear Advance/Pressure Advance on your printer for one of the big ingredients in fixing top gaps and related extrusion inaccuracy problems.

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