The 5-axis CNC machining center features high efficiency and high precision, and the machining of the pentahedron can be completed in one clamping of the workpiece. If equipped with a high-end CNC system with a 5-axis linkage machine, it can also perform high-precision processing of complex spatial surfaces, and it is more suitable for the processing of modern molds such as auto parts and aircraft structural parts.
There are two ways for the rotary axis of the vertical 5-axis machining center. One is the rotary axis of the worktable. The worktable set on the bed can rotate around the X-axis, which is defined as the A-axis. The general working range of the A-axis is +30 degrees to – 120 degrees. There is also a rotary table in the middle of the worktable, which rotates around the Z-axis at the position shown in the figure, which is defined as the C-axis, and the C-axis rotates 360 degrees. In this way, through the combination of the A-axis and the C-axis, except for the bottom surface of the workpiece fixed on the worktable, the remaining 5 surfaces can be processed by the vertical spindle. The minimum division value of the A-axis and C-axis is generally 0.001 degrees so that the workpiece can be subdivided into any angle, and inclined surfaces, inclined holes, etc. can be processed. If the A-axis and C-axis are linked with the XYZ three linear axes, complex spatial curved surfaces can be processed. Of course, this requires the support of high-end CNC systems, servo systems, and software. The advantages of this arrangement are that the structure of the spindle is relatively simple, the rigidity of the spindle is very good, and the manufacturing cost is relatively low. However, generally, the worktable cannot be designed too large, and the load-bearing capacity is also small, especially when the rotation of the A-axis is greater than or equal to 90 degrees, the workpiece cutting will bring a large load-bearing moment to the worktable. The other is to rely on the rotation of the vertical spindle head. The front end of the main shaft is a rotary head, which can surround the Z-axis 360 degrees by itself to become the C-axis. The rotary head also has an A-axis that can rotate around the X-axis, generally up to ±90 degrees or more, to achieve the same function as above. The advantage of this setup is that the machining of the spindle is very flexible, and the worktable can also be designed to be very large. The huge fuselage of the passenger plane and the huge engine casing can be processed at this type of machining center. This design also has a big advantage: when we use a spherical milling cutter to process a curved surface when the centerline of the tool is perpendicular to the processing surface since the linear velocity of the vertex of the spherical milling cutter is zero, the surface quality of the workpiece cut out by the vertex will be very poor. The design of the spindle rotation is adopted, so that the spindle rotates at an angle relative to the workpiece, so that the spherical milling cutter avoids the vertex cutting, and ensures a certain linear speed, which can improve the surface processing quality. This structure is very popular for high-precision surface machining of molds, which is difficult to achieve with rotary machining centers. In order to achieve the high precision of rotation, the high-grade rotary shaft is also equipped with a circular grating scale feedback, and the indexing accuracy is within a few seconds. Of course, the rotary structure of this type of spindle is relatively complex, and the manufacturing cost is also high.
It is generally believed that the 5-axis CNC machine tool system is the only means to solve the processing of impellers, blades, marine propellers, heavy generator rotors, steam turbine rotors, large diesel engines crankshafts, etc. It is a high-tech, high-precision machine tool specially used for processing complex curved surfaces. The machine tool system has a pivotal influence on a country’s aviation, aerospace, military, scientific research, precision instruments, high-precision medical equipment, and other industries…
The use of a 5-axis machining tool makes it easy to clamp the workpiece. There is no need for special fixtures during processing, which reduces the cost of fixtures, avoids multiple clamping, and improves mold processing accuracy. Using 5-axis technology to process molds can reduce the number of fixtures used. In addition, because the 5-axis simultaneous machine tool can save many special tools in processing, the tool cost is reduced. The 5-axis machining tool can increase the effective cutting edge length of the tool, reduce the cutting force, improve the tool life and reduce the cost during processing. Using the 5-axis machining tool to process the mold can quickly complete the mold processing, fast delivery, better ensure the processing quality of the mold, make the mold processing easier, and make the mold modification easier. In traditional mold processing, vertical machining centers are generally used to complete the milling of workpieces. With the continuous development of mold manufacturing technology, some weaknesses of the vertical machining center are becoming more obvious. Modern mold processing generally uses ball-end milling cutters. The benefits of ball-end milling cutters in mold processing are very obvious. However, if a vertical machining center is used, the linear speed of the bottom surface is zero, so the finish of the bottom surface is very poor. , If the four- and 5-axis machining tool processing technology is used to process the mold, the above shortcomings can be overcome.
The furture of 5-axis CNC machining center
- The first is the use of linear motor drive technology. After more than ten years of development, linear motor technology has become very mature. The problem that linear motors are susceptible to interference and large heat generation has been solved. The positioning technology of linear motors not only stops quickly during high-speed movement but also some machine tool manufacturers use damping technology to solve them. The advantages of linear motors are linear drive, no transmission chain, no wear, and no backlash, so they can achieve the best positioning accuracy. Linear motors are highly dynamic, with accelerations exceeding 2g. The use of linear motor drive also has the characteristics of high reliability and maintenance-free.
- Followed by the use of dual-drive technology. For a wider worktable or gantry type, if an intermediate drive is used, the actual driving force cannot be guaranteed to be in the center, and it is easy to cause tilting, resulting in poor dynamic performance. With dual drives, dual gratings, and one drive module, the dynamic performance is perfect. In one drive command, the two drives work at the same time, the grating ruler detects whether the two points are balanced, and if they are not balanced, they are balanced by different commands. Of course, the development of 5-axis machining tool technology is far more than that, and many technologies will be reflected in future machine tool products.
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