Calibrate Filament Flow
To calibrate the filament flow:
Extrusion Multiplier should be set to 1. This is where you make adjustments in case the flow calculations are not quite correct. We will see how it prints at 1, and then change it if needed.
Print the cube and stop it before it begins printing the solid layers for the top. Find the most perfect, best aligned wall and measure it with a caliper.
The first try came out to .51, which means too much plastic is getting extruded. It's a small difference, but if you want to make high resolution prints at a .1mm layer height it can become noticeable. Our target of .42 is about 82% of .51, so set I set the Extrusion Multiplier to .82. This will tell Slic3r to scale back the results of its computations by 82%.