Nov 21, 2019
Five-axis machining , a mode of cnc machine tool machining.
According to ISO, the right hand rectangular coordinate system is used to describe the movement of CNC machine tools. The coordinate axes parallel to the principal axis are defined as z axes, and the rotation coordinates about x, y and z axes are A, B and C respectively. The motion of each coordinate axis can be realized by the table, also can be realized by the motion of the tool, but the direction is defined by the motion direction of the tool relative to the workpiece. Generally, five-axis linkage refers to the linear interpolation movement of any five coordinates in x, y, z, A, B and C.In other words, five axes, x, y, z three moving axes plus any two rotating axes. Compared with the common three-axis (x, y, z three degrees of freedom) machining, five-axis machining refers to the processing of geometric shape more complex parts, the need for machining tools to be able to position and connect in five degrees of freedom. Five-axis machining machine tool is usually called five-axis machine tool or five-axis machining center. Five-axis machining is often used in the aerospace field, processing body parts with free surface, turbine parts and impeller. The five-axis machine tool can process the different side of the workpiece without changing the position of the workpiece on the machine tool, which can greatly improve the machining efficiency of prismatic parts.
5-axis linkage machining center has the characteristics of high efficiency and high precision.If coupled with the high-end CNC system with five-axis linkage, it can also be used for high-precision machining of complex spatial curved surface, which is more suitable for processing modern molds such as auto parts and aircraft structural parts.
There are two ways to rotate the vertical five-axis machining center. One is the rotary axis of the table. The table set on the bed body can rotate around the X-axis, which is defined as the a-axis.There is also a rotary table in the middle of the table. It rotates around the z-axis in the position shown in the figure, which is defined as the c-axis. The c-axis is 360 degree rotation.In this way, through the combination of axis A and axis C, the workpiece fixed on the work table can be processed by the vertical spindle except the bottom surface.
The minimum degree of A axis and C axis is generally 0.001 degree, so the workpiece can be subdivided into any Angle, processing inclined plane, inclined hole, etc..A axis and C axis, such as the XYZ three straight axis linkage, can be processed into A complex space surface, of course, this needs the support of high-grade CNC system, servo system and software.The advantage of this setting is that the structure of the spindle is relatively simple, the spindle is very rigid, the manufacturing cost is relatively low.But the general table can not be designed too large, bearing is also small, especially when the A axis rotation is greater than or equal to 90 degrees, workpiece cutting will bring A lot of bearing torque to the table.The other is to rely on vertical spindle head rotation.
The front end of the spindle is A rotating head, which can rotate around the Z axis 360 degrees and become the C axis. There is also an A axis with rotation around the X axis, generally up to ±90 degrees, to achieve the same function mentioned above.The advantage of this arrangement is that the spindle processing is very flexible, the table can be designed very large, the aircraft's huge fuselage, huge engine shell can be processed in this kind of processing center.This design has a big advantage: we are using spherical milling cutter machining curved surface, when cutting tool processing center line perpendicular to the surface, as a result of the spherical milling cutter vertex linear velocity is zero, the vertices will cut the workpiece surface quality is very poor, adopts the design of spindle, the spindle relative to the workpiece around a point of view, the spherical milling cutter cutting, avoid the vertex ensure that there is a certain linear velocity, to improve the quality of surface processing.This kind of structure is very popular with high precision surface machining, which is difficult for rotary machining center.In order to achieve high rotation accuracy, high-grade rotating shaft is also equipped with a circular grating ruler feedback, indexing accuracy are within a few seconds, of course, this kind of spindle rotation structure is more complex, manufacturing costs are higher.