In general, when the workpiece is not positioned in space, there are six degrees of freedom, X\Y\Z three linear displacement degrees of freedom and its corresponding ah A\B\C three rotational displacement degrees of freedom.
The six degrees of freedom are usually expressed by the X\Y\Z of the Descartes Cartesian coordinate system of three linear axes, with the corresponding A\B\C to express three rotation axes.
Such as multi axis CNC machine tools, that is, the processing center in the design, the need to set the number of axes according to the processing object.
The common market is the three axis CNC machining center, which has three linear displacement axes X\Y\Z. The so-called four axis machining center is generally added a rotating shaft, usually referred to as the fourth axis. The corresponding processing center is the four axis machining center.