My version of a rotary axis simply changes the X linear motion into a rotary one with the driving rollers having the same movement per motor step as the A3 Pro. For such items as glasses the pressure roller can go inside and for plain cylindrical objects on the outside. No calculations needed only decide if the design will fit on so measure round with a tape. As far as the A3 is concerned it is the normal X axis, has the same motor and plugs into the X axis socket. One thing I will mention is the Z axis adjustment was far too little so I had to make an adjustable slide to raise the laser up by about 80 mm to get focus on my intended maximum diameter and flat items and this in turn required me to increase the height inside my enclosure.