The front end of the spindle is a return head, which can 360 degrees around the Z axis and become the C axis. The back 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 above. The advantage of this setting method is that the spindle processing is very sensitive, and the operating table can also be planned very large. The huge fuselage of the passenger aircraft and the huge launching chassis can be processed on this type of vertical machining center.
This plan also has a great advantage: when we use a spherical milling cutter to process a curved surface, when the center line of the tool is perpendicular to the machining surface, because the linear velocity of the pole of the spherical milling cutter is zero, the appearance of the workpiece cut by the pole will be very poor. Adopt the reverse plan of the main shaft, make the main shaft rotate through a viewpoint relative to the workpiece, make the spherical milling cutter avoid pole cutting, ensure a certain linear speed, and improve the appearance processing quality.
Secondly, this structure is very popular with high-precision curved surface machining of molds, which is difficult to achieve with the reverse vertical machining center of the worktable. In order to achieve high precision of reversal, the advanced reversal axis is also equipped with circular scale feedback, and the indexing accuracy is within a few seconds. Of course, the reversal structure of this type of spindle is more complicated and the production cost is also higher.
Worktable reverse axis
The workbench installed on the bed can be reversed around the X axis, which is defined as the A axis. The general operating range of the A axis is +30 degrees to -120 degrees. There is also a reversal table in the middle of the worktable, which is reversed around the Z axis in the orientation shown in the figure, which is defined as the C axis, and the C axis is 360 degrees reversed. In this way, through the combination of the A axis and the C axis, the workpiece fixed on the worktable of the vertical machining center can be processed by the vertical spindle except for the bottom surface.
A-axis and C-axis small division values are generally 0.001 degrees, so that the workpiece can be subdivided into red point of view, and inclined surfaces and inclined holes 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 advanced CNC systems, servo systems and software support. 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.
