Solved Weird surfaces on certain angles

Yea, that is not the issue.

 

I would place 0.3 mm layers at the upper limit of what is reasonable with a 0.4 mm nozzle, especially if you are slightly under-extruding.

 

My rule of thumb is 30-60% of the size of the nozzle, but others ( @Printed Solid ) will vociferously disagree.

 

vociferously disagree might be a bit overstating my opinion. That's a good sweet spot for general printing, but yeah I print outside of that range quite a lot especially on the low end with large diameter nozzles (like .1 - .2 with a .8mm nozzle).

 

But the low end is much more forgiving that the high end. I will stand by my statement that 0.3 mm is at the high end for a 0.4 mm nozzle. My go to layer size with a 0.4 mm nozzle is 0.25 mm layer height. faster than 0.2 mm and not as prone to delamination as 0.3 mm.

 

Glad you are figuring this out. From the second picture I would have told you that the layer height was too big. It just doesn't stick well on the outer perimeter because it has to move too far outward during printing to maintain your shape without using supports.

Plus my personal opinion is that 0.3 mm layers with a 0.4 mm nozzle is the upper limit and won't work in all situations, such as when the overhang angle is too steep. I use about 50° as a rule of thumb and force the slicer to print additional perimeters if needed to help support the overhang. Or just print with supports.

Both @mark tomlinson and @Printed Solid gave suggestions about layer height ranges acceptable for use with a 0.4 mm nozzle. They are both correct depending on the actual model. A model with sloped walls can print fairly thick if the deviation from 90° is small. In general the more the walls slope the smaller the layer height needed to support the angle.

 

Annnnnd there you go

3D printing is still complex. We just do NOT have platform and application support to the level where this can be 'brainless' yet.