There is also a rotary table in the middle of the worktable, which rotates around the Z axis at the position shown in the figure, which is defined as the C axis, and the C axis is 360 degree rotation. In this way, through the combination of the A axis and the C axis, the workpiece fixed on the work table can be processed by the vertical spindle except for the bottom surface. The minimum division value of the A-axis and C-axis is generally 0.001 degrees, so that the workpiece can be subdivided into any angle, and inclined surfaces, inclined holes, etc. can be processed.
If the A-axis and C-axis are linked with the three linear axes XYZ, complex spatial curved surfaces can be processed. Of course, this requires the support of high-end CNC systems, servo systems and software. The advantage of this arrangement is that the structure of the spindle is relatively simple, the rigidity of the spindle is very good, and the manufacturing cost is relatively low. But the general worktable cannot be designed too large, and the load bearing is also small, especially when the rotation of the A axis is greater than or equal to 90 degrees, the workpiece will bring a great load moment to the worktable during cutting.
Another five-axis machining center relies on the rotation of a vertical spindle head. The front end of the spindle is a rotary head, which can rotate 360 degrees around the Z axis to become the C axis. The rotary head also has an A axis that can rotate around the X axis, which can generally reach more than ± 90 degrees to achieve the same function as described above. The advantage of this setting method is that the spindle processing is very flexible, and the table can also be designed very large. The huge fuselage of the passenger aircraft and the huge engine shell can be processed on this type of machining center.