The front end of the spindle is an A-return head, which can rotate 360 degrees around the Z axis and become the C axis by itself. The return head is also equipped with an A-axis that can rotate around the X-axis, generally reaching more than ±90 degrees to achieve the same function as above. The advantage of this setup is that the spindle machining is very sensitive and the work surface can also be large. The huge fuselage and huge starter casing of the passenger aircraft can be machined on this vertical machining center.

This planning also has a major advantage: we use spherical milling cutter to machine surfaces, when the tool machining centerline is perpendicular to the surface, because the spherical milling cutter pole speed is zero, the pole will be cut off the workpiece appearance quality is extremely poor, spindle reverse planning, so that the spindle relative to the workpiece around an angle, spherical milling cutter cutting to avoid the pole, to ensure that the speed must be wired, the processing quality can improve the appearance.

Second, this structure is very popular for high-precision surface processing of molds, which is difficult for the reverse vertical machining center of the workbench. In order to achieve high-precision reversal, the advanced inversion shaft is also equipped with circular grating ruler feedback, and the indexing accuracy is within a few seconds, of course, this spindle reversal structure is more complex and the production cost is higher.