One thing I am curious to know is if you have experienced the Z axis rolling downwards on its own accord -due to the weight- when the stepper is not switched on.

On my milling machine, the weight of the mill head made it freewheel downwards when the power was off. I remedied this by using a belt drive, as opposed to the direct coupling you have on your Z.

I assume the the spindle/mount and sliding plate/rails are not heavy enough to overcome the natural thread retention of the ballscrew, so this may not be an issue at all with a router, as I've seen a lot of guys using direct coupling.

Also, did you go for medium or light preloading for the Hiwin carriages for the Z? I am thinking Medium for the Z, Light for everything else, though I guess it not so important..


Edward