Hi, Neale the missing steps on the z axis is after doing a v carving of a Harley Davidson eagle plaque for example the bit will have raised above the work piece by anything from 1mm to 3.6mm. It is not consistent. I have tried switching drivers from other axis. Changing stepper motors from other axis. I have also changed from 1/8 step to 1/4 stepping, I have tried lowering and raising the amperage settings on the driver. I have also tried slowing the ipm to just 5 with acceleration to 5 and it still raises up from the work piece. I have made numerous different anti backlash nuts and my current design is spring loaded. The only thing that I notice is the alarm led is constantly flickering on and off on the driver when it is changing direction. However all the drivers do this on all of the axis and I do lose steps on my axis just not as much as the axis which is the hard working one.

If I do just normal cutting for example 2d cuts I don't have a problem only when there is a lot of up down movements. At first I thought I may have been my nut but not so sure now.

cheers neil