When I get a new filament I print a few test pieces. One of them is a step shape to allow fine adjustment of the extrusion rate. I am having great trouble getting a good top surface in PETg (2 brands). Have tried just about every setting. The problem seems to be at the edges of the top layer when there is no external 'frame' to stick to. ABS and PLA seem to be ok though. it is much improved with a denser infill. I am aware that I can use a seperate process to increase infill towards the top but for this shape it would need multiple processes.
I guess what Im suggesting is for the slicing software to place a line under the unsupported edge. See below what the unsupported edge looks like.
The ABS at the top is just perfect but it seems that PETg is not good with this overhanging edge
Closeup
All samples have 3 top layers. The first layer layer is terrible but it almost recovers by the 3rd later.
