<p>I've done calibration test with "Concentric circle test" (<a href="https://www.thingiverse.com/thing:11895" rel="nofollow noreferrer">https://www.thingiverse.com/thing:11895</a>) and at specific points there are little bumped points on the print. Also Thingiverse page of the test mentions about these.</p>

<p>How can I solve this problem?</p>

<p>My printer is Creality Ender 3 Pro, I use Esun PLA+ with 210 celcius extruder and 60 celcius bed temperature.</p>

<p>Here is the printed object, both are same print, just took photo on different base.</p>

<p><a href="https://i.stack.imgur.com/53vd2.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/53vd2.jpg" alt="enter image description here"></a></p>

<p><a href="https://i.stack.imgur.com/eqnA7.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/eqnA7.jpg" alt="enter image description here"></a></p>

5 V and 3.3 V are both
logic "highs"
in computing and measured against GND. If the fan simply has to know the on stance and nothing more, then you could run a fan with the logic 5 V (and probably 3.3 V for about 50% spin speed).