Four-axis linkage and five-axis linkage generally refer to the number of linkage control axes of machining center, CNC milling machine or engraving machine control system. Four-axis linkage must first have four controllable axes, and the four axes can control interpolation motion at the same time, that is, the four axes can be controlled simultaneously. This simultaneous motion speed is the synthetic speed, not the individual motion control. It is a point in space moving through four axes at the same time, reaching another point in space and moving from the starting point to the end point at the same time. The motion speed of the intermediate shaft is internally synthesized by the motion interpolation algorithm of the controller according to the programmed speed. For a four-axis machining center, the X, Y and Z axes plus the rotation axis A (which can also be the B axis or the C axis. The a, b and c axes are defined as axes that rotate around the x, y and z axes, respectively. Generally, this fourth axis is the A axis that the A axis rotates around the X axis or the B axis that the B axis rotates around the Y axis, depending on the installation position of the fourth axis on the actual machine tool). This fourth axis can not only move independently, but also. Some machine tools have four axes, but they can only move independently, and can only be used as an indexing axis, that is, stop and lock this axis after rotating to an angle, and only do indexing, which can only be called four axes and three linkages. Similarly, the total number of axes of a four-axis linkage machine tool can be more than four, and there can also be five or more axes, but the maximum number of linkage axes is four.
Five-axis machining means that there are at least five coordinate axes (three linear coordinates and two rotating coordinates) on a machine tool, which can be processed in coordination with movement under the control of a computer numerical control (CNC) system. Linkage means that each axis of CNC machine tool reaches a certain set point at a certain speed at the same time, and five-axis linkage means that all five axes can be used. Five-axis CNC machine tool is a high-tech and high-precision machine tool specially used for machining complex surfaces. This machine tool system has a decisive influence on a country's aviation, aerospace, military, scientific research, precision instruments, high-precision medical equipment and other industries.