[Larken]

Are you using a Linear or Switching [power supply for the 48 volts ? If its a switching, it may be whats making the growling. Especially if its common to all 3 axis.

[Nico13]

Are you using a Linear or Switching [power supply for the 48 volts ? If its a switching, it may be whats making the growling. Especially if its common to all 3 axis.

It is a switching supply and I had noticed the possibility of some harmonics creeping in as my motor speed is beeing set in mm per min small changes of say 30-50mm min would see the motors become noisy and a further shift of another 30-50mm min and they would quieten down again so it could well be related to the power supply.
With my older win XP PC running the machine I can only attain 1000mm per min max reliably but with my otherDesk top machine running Win 7, a dual core AMD processor I can get another 200 mm per min out of it easily and quite smooth and quiet.
So there are a couple of factors influencing it I guess, so I will look around for a second hand later model PC to upgrade to, should help make it a little better over all.

[H500]

It is a switching supply and I had noticed the possibility of some harmonics creeping in as my motor speed is beeing set in mm per min small changes of say 30-50mm min would see the motors become noisy and a further shift of another 30-50mm min and they would quieten down again so it could well be related to the power supply.

If the motors vibrate at certain speeds, then it's resonance. A damper should get rid of it.

As for the missing steps, try inverting the polarity of the step pulses and see if it helps.