Classification of Machine Tools in Five-Axis Simultaneous Machining

This section introduces the structures, characteristics, and development trends of several types of five-axis simultaneous CNC machine tools. It presents several machining models, programming (CAD/CAM systems) and their advantages and disadvantages for five-axis simultaneous machining, and describes in detail the requirements of five-axis CNC machine tools for the CNC system, as well as Sikai's five-axis simultaneous CNC systems. Most of these machines have been continuously imported. Five-axis simultaneous machining centers feature high efficiency and high precision, allowing a workpiece to be machined on five faces in a single clamping. When equipped with an advanced five-axis simultaneous CNC system, they can also perform precision machining on complex freeform surfaces, and are particularly suited for machining complex, high-grade, advanced molds, as well as precision and complex parts such as automotive components and aircraft structural parts. Even now, the export of five-axis CNC systems and machine tools is still restricted to certain destinations. If users employ foreign CNC systems, they must sign strict end-use agreements and accept inspections.

Five-axis simultaneous machining evolved from conventional three-axis machining centers. According to ISO standards, when describing the motion of a CNC machine tool, a right-hand Cartesian coordinate system is used, in which the coordinate axis parallel to the spindle is defined as the Z-axis, and the rotational coordinates around the X, Y, and Z axes are designated as A, B, and C, respectively. The motion of each coordinate axis can be achieved either by moving the worktable or by moving the tool, but the direction is always defined as the direction of the tool relative to the workpiece. Typically, five-axis simultaneous machining refers to linear interpolation motion among any five of the X, Y, Z, A, B, and C coordinates. In other words, five-axis means three linear axes (X, Y, Z) plus any two rotary axes. Based on the arrangement of the tilting axes, five-axis machines can be classified as follows.

1. Table cradle type: Based on a traditional three-axis machining center with an added cradle-style worktable, the workpiece tilts, forming a 3+2 type five-axis simultaneous machining center. The simultaneous axes are X / Y / Z / A / C, with the B-axis not rotating in the Y-axis direction.

2. Vertical spindle double swing head type: In the center of the swing head, there is typically a motorized spindle with a power drawbar mechanism, so the size of the double swing head itself is not easy to make small. Combined with the required range of motion of the double swing head, the machining range of five-axis simultaneous machine tools with a double swing head structure should not be too small but rather suitable for shorter travels, generally using a gantry or moving beam gantry design. The simultaneous axes are X / Y / Z / A / C, with the B-axis not rotating in the Y-axis direction.

3. Horizontal spindle double swing head type: A five-axis simultaneous machine with a double swing head based on a horizontal machining center structure. The simultaneous axes are X / Y / Z / B / C, with the A-axis not rotating in the X-axis direction.

4. Table tilting type: After direct drive motors became mature, the structure of five-axis simultaneous machining was also greatly improved. The entire worktable can perform dual-axis tilting. Nowadays, direct drive of the C-axis can achieve sufficient speed to enable turning operations. The simultaneous axes are X / Y / Z / B / C, with the A-axis not rotating in the X-axis direction.

5. Table and spindle tilting type: Based on the evolution of tilting arrangements, the worktable and the spindle tilt separately, forming a combination of both. The simultaneous axes are X / Y / Z / A / C, with the B-axis not rotating in the Y-axis direction.