The development trend of five-axis simultaneous machining center

Machining Center

The five-axis simultaneous CNC machining center is characterized by high efficiency and precision, allowing the processing of a five-sided body to be completed in a single clamping of the workpiece. When equipped with an advanced five-axis simultaneous CNC system, it can also perform high-precision machining of complex spatial surfaces, making it more suitable for processing modern molds such as automotive components and aircraft structural parts. There are two types of rotary axes in a vertical five-axis machining center. One is the worktable rotary axis, where the worktable mounted on the machine bed can rotate around the X-axis, defined as the A-axis, with a typical working range of +30 degrees to -120 degrees. There is also a rotary table in the middle of the worktable, which rotates around the Z-axis as shown, defined as the C-axis, with a 360-degree rotation capability. Through the combination of the A-axis and C-axis, all five faces of the workpiece fixed on the worktable, except for the bottom face, can be machined by the vertical spindle. The minimum indexing value of the A-axis and C-axis is typically 0.001 degrees, allowing the workpiece to be subdivided into any angle and machined with inclined surfaces and holes. If the A-axis and C-axis are linked with the XYZ three linear axes, complex spatial surfaces can be machined, although this requires the support of high-end CNC systems, servo systems, and software. The advantage of this setup is that the spindle structure is relatively simple, with excellent rigidity and low manufacturing costs. However, the worktable generally cannot be designed too large, and its load-bearing capacity is relatively small. Especially when the A-axis rotates at an angle greater than or equal to 90 degrees, the workpiece cutting will exert a significant bearing moment on the worktable.

The other type relies on the rotation of the vertical spindle head. The front end of the spindle is a rotary head that can rotate 360 degrees around the Z-axis, defined as the C-axis. The rotary head also has an A-axis that can rotate around the X-axis, typically reaching ±90 degrees or more, achieving the same functionality as described above. The advantage of this setup is that the spindle machining is very flexible, and the worktable can be designed to be very large, allowing for the processing of large aircraft fuselages and enormous engine casings on this type of machining center. Another significant advantage of this design is that when using a ball-end mill to machine a curved surface, if the tool centerline is perpendicular to the machining surface, the surface quality of the workpiece cut by the tool tip will be poor because the linear speed of the ball-end mill tip is zero. By adopting a spindle rotation design, the spindle can be rotated relative to the workpiece to avoid cutting with the tool tip, ensuring a certain linear speed and improving surface machining quality. This structure is highly favored for high-precision curved surface machining in molds, which is difficult to achieve with worktable rotary machining centers. To achieve high-precision rotation, high-end rotary axes are also equipped with circular grating rulers for feedback, with indexing accuracy within a few seconds. Of course, the rotary structure of this type of spindle is relatively complex, and the manufacturing cost is higher.

Development Trends

1. The first is the adoption of linear motor drive technology. After more than a decade of development, linear motor technology has matured significantly. The issues of susceptibility to interference and high heat generation when linear motors were first developed have been resolved. Some machine tool manufacturers have also adopted damping technology to address the positioning technology of linear motors, enabling rapid stopping during high-speed movement. The advantages of linear motors include linear drive, no transmission chain, no wear, and no backlash, resulting in optimal positioning accuracy. Linear motors have high dynamic performance, with acceleration exceeding 2g. The use of linear motor drives also offers advantages such as high reliability and maintenance-free operation.

2. The second is the adoption of dual-drive technology. For wider worktables or gantry-type configurations, if central drive is used, it is practically impossible to ensure that the driving force is centered, which can easily cause tilting and result in poor dynamic performance. By using dual drives, dual grating rulers, and a single drive module, excellent dynamic performance can be achieved. With a single drive command, both drives work simultaneously, and the grating rulers detect whether the two points are balanced. If they are not, different commands are used to achieve balance. Of course, the development of five-axis simultaneous machine tool technology goes far beyond these, and many technologies will be embodied in DMG MORI's machine tool products. Five-axis simultaneous CNC machining center.