I have blown a single pin on an Arduino Mega2560(datasheet: http://www.kynix.com/uploadfiles/pdf8827/ATMEGA2560-16AU.pdf). This is the 'step' pin of the Z axis on a 3D printer. The stepper driver is configured for 64 micro pulses per step (25600 per revolution). The mechanical arrangement is T10 timing belt on 16 tooth pulley, approx 1000mm/minute max travel speed, 200step/rev motor geared 12.5:by Olsla - Controllers