I have an Ender 3 with a lot of mods. Of note, a cheap direct drive kit, linear rails for the Y axis, an upgraded "silent" mainboard and TH3D's firmware. But this issue goes back a long ways, yet I've not seen any really good examples of this particular issue in various faqs.
All of my vertical edges, especially when they are 90°, have raised lips in a very precise, repeated fashion. It's small, maybe a quarter millimeter in diameter, so it rarely is a problem, but occasionally it messes with the dimensionality of a print with tight tolerances.
I had suspected the problem might have been related to using acceleration/jerk settings, but I disabled them for the print below and got a perfect example case.
Other things I've tried:
- calibrating E-steps (I've done this many, many times, only to find the E-step number changes with speed and temperature anyway).
- Deliberately underextruding. This actually doesn't help.
- Slowing prints way, way down. Also doesn't seem to have an impact, at least down to 20mm/s.
- changing slicers. This problem happens with Cura, Simplify3d and PrusaSlicer.
- replacing my nozzle with a fresh one, which should have cleared up any existing clogs or leakages from a worn nozzle.
After a lot of searching on the subject, I found this bug report for Marlin, the first case of over-extruded corners I've found that look at all like mine. What I find especially interesting is that changes to Marlin around version 1.1.8 have introduced the issue for some people who previously didn't have the problem. This seems to suggest it's not necessarily a hardware issue, but a bug in software. I'm considering testing out a downgrade to a 3-year-old version just to see if that alone makes a difference.