Totally agree with @Misterg - except that last plunge is way deeper than the previous reductions in Z height. It looks to me as though there is both binding close to the top of Z travel and hitting the top of Z travel so I think you are losing variable numbers of steps. Do you have hard limits enabled? If so that would suggest a lot of binding. What are your Z retract height settings? Haven't used Carveco for a while so can't remember what they call it. Can you show us a video showing the whole of the Z axis when it's doing that? Alex.
I now have a functioning CNC my problem now is the accuracy when cutting circles. Its a ball screw machine no belts is it to do with synchronisation of the motors?
no, your machine has backlash, lots of it. this means that when a motor turns the carriage does not follow it exactly because of 'soemthing loose somewhere'. the grub screw in the motor coupler must be on the flat of the shaft grubs screws onto the leadsscrew must be tight nutblocks must be tight to the carriage and properly adjsuted for low friction and zero play. wheels must be properly adjusted. router must be mounted stiffly, I used 2 mounting rings on mine to stop it flexing.
