When we are saying 4 Axis CNC Router Machine, it is basic 3 Axis cnc machine + a 4th Axis. and what is the 4th Axis?
The 4th Axis may be a Rotary turning device, like a lathe, which makes workpiece turning during processing Irregular Cylinder Carving, such as Sculptures, furniture legs, stair handrails and so on.
It also may be a spindle that able to rotate/swing by the vertical axis. Comparing with up-down motion of basic 3 Axis’ spindle, CNC Router with Swinging Spindle can process a more complex figure and do advanced working.