PS 2.9.4 adding variable width lines to first three layers of vase mode
I'm baffled by what is happening in PS on this model. This is a thin wall model with the wall thickness set to the extrusion thickness in PS. The first three layers are extruded in a clearly jerky fashion during printing, and looking at the code, instead of using a uniform width for the extrusion, it's varying wildly from 0.47 to 0.79mm. The width of all layers is set to 0.8mm (0.4mm nozzle, eSun PLA-LW expanding filament with a 0.5 extrusion factor / 200% expansion at 270-280C).
Once the slicer gets to layer 3, ~0.6mm, it switches to a uniform extrusion at 0.8mm, but the bottom of the print is just trash when this happens.
Edit: I've checked that it's not in the Fusion output by sinking the file 1-3mm into the bed. Regardless of the start point on the cylinder, everything above the 3rd layer is uniform and thee first layers are variable width. However, using a PrrusSlicer primitive cylinder at the same size does not produce the first layer variable width.
PS-
As a side note, can PrusaSlicer do G2 / G3 moves? I've previously use Cura with ArcWelder to produce 3D curves for cylindrical vase mode prints, but no matter how fine I set the export options in Fusion all I get are G1 moves and very approximate cylinders (compared to the accuracy of the model), even with G2/G3 enabled and slice/gcode resolution set to 0.
RE: PS 2.9.4 adding variable width lines to first three layers of vase mode
Found the error: PS disables the "Minimum Bottom Thickness" when entering Spiral Vase mode but does not set the Minimum Bottom Thickness to 0. I had 0.7mm as the default minimum bottom, which was grayed out an inaccessible in Vase mode. In fact, setting the Bottom (or top) to 0 layers grays out the minimum shell thickness in all cases. However, even with the number of bottom layers set to 0, PrusaSlicer attempts to create the number of bottom layers previously set. Unchecking Vase mode, increasing the bottom layer to 1, then setting the minimum bottom thickness to 0, changing the bottom layer count back to zero, and re-enabling Vase mode fixed the problem.
I suspect that the <0.02mm variation in wall thickness of the tessilated STL model (nominally 0.8mm wall in model and 0.8mm external wall extrusion thickness setting) is causing the variable wall thickness result. Of course, it's doing a terrible job at it with the variable layer width, but that's an idiosyncrasy of the arachne algorithm (classis is even weirder, with skipped areas entirely). How do I know it's the wall thickness in the STL? Well, setting the extrusion width to 7.9mm fixes all both 2-3 locations where it goes bonkers with the line width, and setting it to 7.8 fixes the variable extrusion problem in the Gcode - though dropping to ~7.6mm results in two lines on the first layer(s), which is also an undesirable result (for my part).
RE: PS 2.9.4 adding variable width lines to first three layers of vase mode
Geometry with thin walls is not generally suited to printing in vase mode. Vase mode is generally used with solid objects to print in effect the exterior shell.
You would need to post an example project from PS (save project as) and then zip up the 3mf to attach here to get any useful help.
Current versions of PS do support G2/G3 move conversions as long as the option is set in your print profile. Print Settings>advanced>Slicing>Arc Fitting. Need to be in advanced or expert mode to see the setting.
Again if you had attached a project file that would contain all the settings you are slicing with so people would be able to see and debug issues and have more info to base answers on.