Oh Prusa Slic3r, why you do this to me... over-extrusion and blobs and stuff. Started print the parts for the Z-rails and having a hard time to get the parts to print with decent quality. For most part Prusa Slic3r has been working ok, quality has been decent and consistent. But for some reason the rail parts are hard for the slicer. Switched to KISSlicer to see if the problems persist and lo and behold, pristine quality (Slic3r on the left, KISS on the right):

https://www.dropbox.com/s/iuqovg1dds...20.42.jpg?dl=0
https://www.dropbox.com/s/r89p7yanfu...21.18.jpg?dl=0
https://www.dropbox.com/s/duyaqt57me...21.36.jpg?dl=0

I guess the slope on the rail is the problematic are, as Slic3r tries to ensure vertical shell thickness and does it over somewhat. I haven't seen this problem this strong even though there have been some hints about Slic3r extruding more material than S3D and KISS. Also I've upgraded my Prusa MK2 with E3D Titan, which is a geared extruder (it's calibrated properly).

Switching slicing sw mid project isn't something I like to do because it's yet another variable and might cause problems when fitting parts together. But slicer starts to misbehave, alternative is to spend extra time with post processing, which I'd like to do without as much as possible. So KISS it is, at least for these rail parts.

Other progress: I have the z-screw - bed carriage part somewhat finished. But I'd really like to make the rail sliders replaceable, so one doesn't have to reprint the whole z-screw part when replacing them so going to do some more tweaking. Onto OpenSCAD ->