It’s not top thickness, that’s only 3 layers and the bulge is on more layers than that.
Printed with PLA, 4 perimeters, 15% gyroid, but no infill makes difference, i don’t think this is about shell thickness.
Retraction is good, there is no oozing on retract moves and no stringing on the printed parts.
Otherwise the prints come out okay so i’m a bit stuck with this one!
You can see the bulging in all three edges on the picture, about 3-4mm from top to bottom, then a few ok layers, then again a few layers with bulges on corners.
Slicer is Prusa if that’s relevant.
Any ideas are welcome!
For me that looks like slight overextrusion of the top layers. The first few layers are also slightly squished out. The Calibration Cube is a very extreme example. Before you start adjusting I'd print something more natural and if you don't like that you can go through this: https://teachingtechyt.github.io/calibration.html
First layer is printed with 0,8mm and half as fast as the others, then the second layer i believe is regular width but still half the speed, that’s why it’s a bit squished down there.
I was mainly worried about the top, as i didn’t set anything speed or extrusion related for anything apart from the first two layers mentioned.
Otherwise, prints are okay, but i like to print a calibration cube every now and again just to check for possible maintainance required.