<p>I have an Ender 3 Pro modded with the Hero Me Gen 6 air ducts, installed a Creality 4.2.7 mainboard, and updated Marlin firmware to the latest for now 2.1.1 version. I'm printing with PLA only.</p>
<p>It was printing well enough. The nozzle started to wear down so I replaced the nozzle (standard brass one) but also upgraded the heatbreak to a bi-metal one (not all-metal, there is still a plastic tube inside the heatbreak) and a heatblock (standard goldish Creality block). And since that moment, the printer fails to print with good quality starting the second layer</p>
<p>What I tried:</p>
<ul>
<li>recalibrated it with a gauge of 0.2 mm and the first layer is perfect (did not know that could be a thing :))</li>
<li>updated firmware</li>
<li>tried to tighten screws (as it is recommended <a href="https://3dprinting.stackexchange.com/questions/5503/has-anyone-encountered-this-type-of-strange-print-patterns">here</a>)</li>
<li>adjusted Z-axis steps/mm</li>
<li>another filament</li>
</ul>
<p>I can't figure out what causes that thing.</p>
<p><a href="https://i.stack.imgur.com/NpYMj.jpg" rel="nofollow noreferrer" title="Photo of the first two layers of a printed model; the second layer looking very different"><img src="https://i.stack.imgur.com/NpYMj.jpg" alt="Photo of the first two layers of a printed model; the second layer looking very different" title="Photo of the first two layers of a printed model; the second layer looking very different" /></a></p>
<p><a href="https://i.stack.imgur.com/NPZVO.jpg" rel="nofollow noreferrer" title="Upclose photo of the printed model showing the difference in the two layers"><img src="https://i.stack.imgur.com/NPZVO.jpg" alt="Upclose photo of the printed model showing the difference in the two layers" title="Upclose photo of the printed model showing the difference in the two layers" /></a></p>
<p><a href="https://i.stack.imgur.com/SKahg.jpg" rel="nofollow noreferrer" title="Zoomed in photo of the printed model showing the detailed differences in the two layers"><img src="https://i.stack.imgur.com/SKahg.jpg" alt="Zoomed in photo of the printed model showing the detailed differences in the two layers" title="Zoomed in photo of the printed model showing the detailed differences in the two layers" /></a></p>
<p>edited 2022-10-25 23:41</p>
<p>I think it is overextrusion. I tried reprinting object. The first layer was perfect, but second was poor again. There was no difference with cooling or without, no difference printing slower. But flow rate did matter:</p>
<ol>
<li>100% flow rate</li>
<li>changed to 85% flow rate</li>
<li>changed to 75% flow rate</li>
<li>changed to 100% flow rate</li>
<li>changed to 75% flow rate</li>
</ol>
<p>Maybe it is prusa slicer doing its thing. I will try Cura. The only thing that bothers me is that diagonal scratch - that is from the nozzle which makes me think it is too low for the second layer</p>
<p><a href="https://i.stack.imgur.com/j0wWW.jpg" rel="nofollow noreferrer" title="Difference of other flow rates"><img src="https://i.stack.imgur.com/j0wWW.jpg" alt="Difference of other flow rates" title="Difference of other flow rates" /></a></p>
<p>edited 2022-10-28 15:53</p>
<p>It's not a slicer thing. I sliced object with Cura and got pretty much the same result. I babystepped z-axis during the print to get nice result. So I think it is either z-axis motor not stepping enough or I need to lower extrusion multiplier in slicer. I will print calibration cube to check if z-axis motor steps up enough</p>
<p>edited 2022-10-28 18:34</p>
<p>Printed calibration cube. Turns out my z-axis steps were off. Model was 19.66mm instead of 20mm. I tuned steps to 407 from 400. That helped a bit (model is 20.02mm now) , but still the same ugly overextruded result. Tried to lower extrusion multiplier to 0.8 and still got the same bad result</p>
<p>edited 2022-10-30 22:11</p>
<p>It is neither nozzle nor heatbreak tube. I checked it using my old hardware. Maybe it is somehow connected to firmware... Or E-steps are off while printing</p>

[{'answer_id': 20126, 'author': 'Kilisi', 'author_id': 31811, 'author_profile': 'https://3dprinting.stackexchange.com/users/31811', 'pm_score': 1, 'selected': False, 'text': '<p>I would go back to the brass nozzle and try again for comparison.</p>\n<p>We had a batch of 10 cheap steel nozzles all of which caused problems.</p>\n'}, {'answer_id': 20154, 'author': 'evgen-baton', 'author_id': 35836, 'author_profile': 'https://3dprinting.stackexchange.com/users/35836', 'pm_score': 0, 'selected': False, 'text': '<p>I think the answer is printing temperature. This shiny PLA I\'m using is Eryone Silk PLA. Although the working temperature is stated as 190-220\xa0°C, my 205\xa0°C was too much for it. A temperature of 190-195\xa0°C produces good results though not as shiny anymore. It is three layers printed on the sample below with no problems.</p>\n<p><a href="https://i.stack.imgur.com/tJP8x.jpg" rel="nofollow noreferrer" title="3D printed sample printed with 195 degrees Celsius and showing no printing errors"><img src="https://i.stack.imgur.com/tJP8x.jpg" alt="3D printed sample printed with 195 degrees Celsius and showing no printing errors" title="3D printed sample printed with 195 degrees Celsius and showing no printing errors" /></a></p>\n'}]
['https://3dprinting.stackexchange.com/questions/20124', 'https://3dprinting.stackexchange.com', 'https://3dprinting.stackexchange.com/users/35836/']