The issue I’ve recently experienced is specific to TPU, but I’ve seen it in the past to a lesser degree with other filaments as well.
For context, from what I’ve observed, when filament is extruded along a path there is a varying degree of tension on the ‘line’, even though it’s molten. This tension appears to be more extreme with TPU. When printing a concave overhang feature, I’ve noticed this tension tends to curl specifically the exit corner of the concave feature upward - especially if the feature is small.
I’ve adjusted temp, speed, and cooling settings and I don’t think they alone can solve the issue, which I believe can be proven from the photos, where the ‘entry’ side of the mirrored feature prints near perfectly, but only the exit has the curl.
I think having the ability to alternate the perimeter path direction (CW, CCW) for each sequential layer would solve this issue by distributing the tension direction to both sides of the feature - currently, with the tool-path being the same direction for each layer, the error compounds and the corner keeps curling. From what I’ve read, Orca slicer has this feature and other slicers may as well.
