Cura is driving me nuts with a particular issue: I'm getting under-extrusion as you can see here: http://imgur.com/a/hKNSg.
It only occurs where an internal feature (internal walls for a hole in this case) is printed immediately before start of an external wall, and the under-extrusion is only at the first sections of the walls that print right after the internal hole wall. I've tried everything I can think of, changing temperature, speed, enabling "Retract Before Outer Wall" in case it was a wiping issue, trying various retract settings.
The only thing that made it go away with Cura was editing the .stl to remove the screw holes, which obviously is not ideal. ;-) Craftware with equivalent settings did not have the under-extrusion problem.
Settings: Default cura Draft 0.2 profile, with the following changes:
Wall thickness - 1.2mm
Infill density - 30%
Printed in Hatchbox Blue PLA, which I've used for many other prints without issue. Printed on my Monoprice Maker Select v2, with DII cooler at 40% and upgraded extruder gear. E-steps were calibrated, PID has been tuned. Bed was heated to 60 degrees.
Settings I tried to play with:
Temperature: 205,210
Speed: 60mm/s, 50mm/s
Retract Before Outer Wall: False,True
Enable Coasting: False, True
Retraction Distance: 6.5mm, 2.5mm, 2.0mm
Retraction Speed: 40mm/s, 20mm/s
None of it made a lick of difference one way or another, however the instant I used meshmixer to remove the screw holes from the model the under-extrusion went away... I've seen similar issues before, but only now did I have the tools to examine the gcode to see the print order and have to print enough parts (needed 8, printed even more) to be able to remove other possible variables. I'd love to hear otherwise, but pretty sure something is screwy in Cura here, and hope I've collected enough data to help figure out what it is.
The original STL is available here: https://www.thingiverse.com/thing:1033845/#files
I'd be happy to post my modified "no screws" STL if anyone wants it for testing, as well as any gcode that might be useful.