Structure Of Machining Center Of 5-Axis Linkage CNC Machine Tool

Most of the 5-axis linkage machining centers have a "3+2" structure, that is, the three linear motion axes of X, y and Z plus two rotation axes of a, B and C rotating around the X, YZ axis respectively. In this way, there are x, y, Z, a and B in terms of classification; X，Y，Z，A，C； 10. There are three forms: y, Z, B and C. According to the different combination forms of the two rotating shafts, there are generally three forms: double rotary table, turntable plus swing head and double swing head. Due to physical reasons, these three structural forms determine the size of the 5-axis linkage machine tool and the range of processing objects.

1. 5-axis linkage machine tool with double turntable structure

The workbench 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° to 120°. There is no rotary table in the middle of the workbench that rotates around the z-axis, which is defined as the c-axis, which can generally rotate 360°. In this way, through the combination of a-axis and c-axis, except for the bottom surface of the workpiece fixed on the workbench, the other five faces can be processed by the vertical spindle. The small division value of axis A and axis C is generally 0.001°. In this way, the workpiece can be subdivided into any angle to process inclined plane, inclined hole, etc. If the a-axis and c-axis are linked with the three linear axes of X, y and Z, complex spatial surfaces can be machined. Of course, this requires the support of NC system, servo system and software. The advantages of this setting method 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, the general worktable cannot be designed to be too large and bear less load. Especially when the rotation of axis A is equal to 90°, the workpiece cutting will bring great cutting torque to the worktable.

2. 5-axis linkage machine tool with turntable and swing head structure

Since the turntable can be a-axis, b-axis or c-axis, as well as the swing head, which can be a-axis, b-axis or c-axis respectively, the 5-axis linkage machine tool with turntable and swing head structure can have various combinations to adapt to different processing objects. The advantage of this setting method is that the spindle processing is very flexible, and the worktable can also be designed to be very large. The huge fuselage and engine shell of the airliner can be processed on this kind of processing center. This design also has a great advantage: when using the spherical milling cutter to process the curved surface, when the tool center is perpendicular to the machining surface, the surface quality of the workpiece cut by the vertex will be very poor due to the zero vertex linear speed of the spherical milling cutter. The design of spindle rotation is adopted to make the spindle turn an angle relative to the workpiece, so that the spherical milling cutter can avoid vertex cutting, ensure a certain linear speed, and improve the surface processing quality.

This structure is very suitable for die high-precision surface machining, and it is also difficult for worktable rotary machining center to do. In order to achieve the high precision of rotation, the rotary shaft is also equipped with circular grating ruler feedback, and the degree of division is within a few seconds. Of course, the rotary structure of this kind of spindle is complex and the manufacturing cost is high.

3. 5-axis linkage machine tool with double swing head structure

Due to the structure itself, there is generally an electric spindle with a loose broach structure in the middle of the swing head, so the size of the double swing head itself is not easy to be reduced, generally 400-500mm. In addition to the needs of the activity range of the double swing head, the processing range of the 5-axis linkage machine tool with the double swing head structure should not be too small, but the larger the better. It is generally gantry type or moving beam gantry type, and the width of the gantry is more than 2000-3000mm.

At present, the swing head structure of the more advanced double swing head 5-axis linkage machine tool generally adopts the torque motor of "zero transmission" technology. The application of "zero transmission" technology in the rotating shaft is an ideal technical route to solve the rigidity and accuracy of its transmission chain. With the development of technology, the manufacturing cost of twist short motor has decreased greatly, and the market price has also decreased. This process will promote the manufacturing technology of 5-axis linkage machine tool to further advance.