Pronounced layer lines on stacked cubes
I am trying to resolve a performance issue with my XL. If I have a 20x20x10mm rectangle with a 10x10x10mm rectangle on top of it with one side aligned, we get a VERY distinct layer line between the changes in geometry on the shared face. The model in autocad does not have any issues that we can see. We have modeled different things and every time we do this sort of thing it happens. Different filament types, different models. We can't figure it out. Please help
It may be an Autocad setting - do you have chamfered edges? Does the preview in Prusaslicer show the issue?
Cheerio,
RE: Pronounced layer lines on stacked cubes
The slicer does not show the issue. the models do not have any bulges in those areas. this is two different filament types (ABS, and PLA) and obviously two different models with the same behavior. 
OK, a small experiment:
Design a simple part in two different ways.
Make a shape by placing one smaller cuboid on top of another.
Make the same shape from a cuboid that encloses the whole by subtracting negative shapes to whittle it to size.
Slice and print both.
I suspect that Autocad is outputting two primitive shapes with their perimeters touching so that the extra filament in those adjacent top and bottom layers is distorting the surface as it cools. The subtractive version shouldn't have any extra internal perimeers and, with luck, should give the required output.
Cheerio,
RE: Pronounced layer lines on stacked cubes
20x20 base 10x10 top, one made subtractively one made additively. Same behavior on both prints
Interesting. I created a similar file using OpenSCAD and it printed OK - attached below.
I sliced for 0.6mm nozzle, 0.25mm SPEED, with 20% cubic infill.
Try it.
Cheero,
RE:
I had the issue as Diem it described.o, but on the Prusa Mini.
I was using Tinkercad where two cubes were separate objects - so in the slicer the perimeters were generated for each object separately and thus the connected part between the object was printed differently.
When merging models prior importing to the slicer the issue disappeared.
You can see it after slicing and looking a preview layer per layer by scrolling vertical scroll bar on the right.
Yet for some models I get some visible layer quality differences when geometry changes and it is related to the print speed in those areas, so maybe it is worth to look at the speeds settings. This is especially visible in the image higher ( the box with little legs on the right), on the left part of the print.
See my GitHub and printables.com for some 3d stuff that you may like.