Then no one has told either Biesse or Morbidelli about that! The technique used on many of their machines (including ours) is to use an "air cylinder". This uses compressed air to act like a damper on Z-axis movement and assists in raising the Z-axis back to its upper limit stop. I have also seen this system used on some of the older SCMs and Wadkins. I reckon counterweights would suffer from many problems. Firstly you are adding to the weight caried by the Y-axis gantry, secondly you are going to have to secure them in slides to prevent them moving around when the machine is in motion (and ours will happily cut in X- or Y- directions at 14m/minute with jogging at about 60m/min). I think that the speeds at which woodworking CNCs accellerate depending on gravity might be just a little too slow, unless the weight was enormous.
