Perimeter separation problems
So, I'm printing out face shield headbands to donate to a local hospital for all the coronavirus craziness, and I'm having some issues with the perimeter walls having separation in some spots. I could really use some advice. I have an Ender 3 and use Repetier Host Mac with Slic3r. With a 0.4mm nozzle, I'm running it at a 0.32 layer height, 30% infill, 80mm/s speeds. I've done lots of calibrations... measured filament diameter, esteps, retraction, flow rate, temp towers. I've even experimented with the extruder multiplier factor a bit, but increasing it gives me too much stringing. I've improved things from the first prints, but I still get some trouble. I sliced the stl with auto/default extrusion width settings, but I'm thinking I may need to mess with that... set specific widths? But, I'm really not sure at all where to begin with that, since using the auto settings, it doesn't tell you what the actual widths are. The Prusa stl page is https://www.prusaprinters.org/prints/25857 if that helps at all.
Any help with any of this would be greatly appreciated!