If the problem improves with fewer walls, it is probably also an extrusion problem. This is because changes in extrusion have a greater effect with more walls. If you have a slight over-extrusion, this is hardly noticeable with 2 walls, if you use 4 walls you will see it better. Above a certain number of walls, the problem may no longer change in terms of visibility. A flow ratio of 1.029 is definitely too much. The K-factor also has an effect. In some experiments I have learned that the K-factor is not unimportant. Depending on the filament and its properties (e.g. moisture content), a slight deviation (e.g. 0.00…) in the K-factor can show up in the print image. I can only report on practical experience in case anyone thinks that this should not be the case in theory. It is therefore important that you set the filament parameters correctly.
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create a profile for your filament by first selecting a generic profile for your filament material and saving it under a different name
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enter the print temperature and the temperature range at which the print will be performed
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first leave the flow ratio at the default value (0.98 for example, which is pre-entered) and also the value for mm³/s
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save the profile
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make sure the filament is dry. PLA is easy to dry, do this as a precaution if you are unsure
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Calibrate the K value for your filament with the profile you have created using manual calibration
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Save the K-value for your filament
If you change the above values, flow rate (mm³/s), flow ratio and temperature or if your filament has not been dried for a long time, then recalibrate the K-value.
Another note: if you use the automatic calibration for the flow ratio, you may get incorrect values. I have experienced this myself with black PETG. I also got a value of 1.026 or similar, which was far too much, I noticed this in the accuracy of fit of the parts that I had previously printed in PLA and everything was right there.
Have a nice day!