In the BB Manual - first print - it says, after inserting the filament, simply "Adjust the tension of the Filament Idler" How do you do that? To what criteria? All has been well until now - and e3d PLA was at 304 e-steps spot on - but ramped the Volcano up to 0.6mm layer heights, 1.25mm extrusion width and 50mm/s: the idler began to slip and skip horribly. So the question now is begging. How do you set the filament idler right?
There is a hex screw to the left of the idler (the one above the spring). You have to adjust this screw.
Apparently the limit is 40mm3/s. I identified the hex nut alright (it helps having assembled the printer!) but my question is, how tight should the idler be? Or, how loose should the idler be? What's the trick for getting it right?
You should turn the hex anti clockwise (that should give the grub screw more grip). One turn for a starters should be enough, this is a bit trial and error.
There is no rule, it depends on the filament and the object to print. It's more important for small parts with a lot of retracts and less important for bigger parts. In general, you must see a nice trace of teeth without having the filament pressed, must still be round form. If the extruder skips forth and back, normally it's too much pressure, but could also be the temperature too low. With motors disabled, heat up the hotend and push the filament by hand, this can give you a feeling.