I've been using a Faberdashery PLA 3MM filament for my Ultimaker 2. When printing layers sloping outwards (or mild overhangs), the printer seems to feed too much material. Excess starts to add up with every layers until the surface gets messed up. I tried tuning the material flow settings (reducing to 95-97%) while printing, however, the results are not always consistent. Sometimes, the Ultimaker leaves tiny gaps when printing with reduced flow which then leads to further errors.
I suspect I need to calibrate the filament diameter settings or the feed rate (i.e. related between feed speed and filament diameter). Any advice how to do this properly?
UPDATE. Image attached.http://imgur.com/lAf7k5e