The CNC milling machine is developed on the basis of the general milling machine. The processing technology of the two is basically the same and the structure is somewhat similar, but the CNC machine tool is an automatic cnc machine controlled by the program, so its structure is also very different from the ordinary milling machine. .

In order to further shorten the non-cutting time, some machining centers are equipped with two pallets that automatically exchange workpieces. One is loaded with workpieces to be processed on the worktable, and the other is loaded and unloaded outside the worktable. After the machine tool completes the processing cycle, it automatically exchanges the pallets, so that the time for loading and unloading the workpiece coincides with the cutting process. Machining centers are usually classified according to the relative position of the spindle and the table, and are divided into horizontal, vertical and universal machining centers.

• (1) Horizontal machining center: refers to the machining center where the axis of the spindle is parallel to the worktable, and is mainly suitable for machining box parts.
• (2) Vertical machining center: refers to a machining center where the axis of the spindle is perpendicular to the worktable, and is mainly suitable for processing complex parts such as plates, discs, molds and small shells.
• (3) Universal machining center (also known as multi-axis linkage machining center): refers to a machining center that can control the linkage change through the angle between the machining spindle axis and the table rotation axis to complete the machining of complex space curved surfaces. It is suitable for the precision machining impeller rotors, molds, cutting tools and other workpieces with complex spatial curved surfaces.