I'm in the last steps of assembling my bq Prusa i3 Hephestos. I found in the annex the topic "driver calibration" and I'm not sure if it's necessary to perform? Or is it already calibrated from bq?
They are already calibrated, so it is not necessary. :-)
Calibration is indicated only if you notice abnormal behaviours in the movement of the motors along the three axes. This may happen after a long time using the printer or, in some rare cases, right after assembling it. If the drivers needed calibration you would definitely notice it when you start using it as the prints would not be accurate at all (motors could skip steps, etc.).
Even if they're pre calibrated from the factory,
just check the values are good :
MotorCurrent(A)*8*Rs=Vref
Rs depends of your drivers resistance (0.05 to 0.2)
++JM
Edited 1 time(s). Last edit at 10/22/2015 10:26AM by J-Max.