NUMERICAL CONTROL MACHINE TOOLS

The most important types of NC machine tools are:
1. NC drilling machines. An NC drilling machine holds, rotates, and feeds the drilling tool into the WP. They are available in a wide range of types and sizes that are built with single spindle or multiple spindles. Some machines are equipped with turrets and others with tool-changing mechanisms. Either two or three axes is available, and some drilling machines are even capable of performing milling operations.
2. NC milling machines. These machines (Figure 8.27) are used to machine l at surfaces and produce contours and curved surfaces. The orientation of the spindle may be horizontal or vertical and provided with single spindle or multiple spindles. Milling machines with two perpendicular spindles provide machining a hole and a vertical surface simultaneously. Such a facility is useful when machining large components, as shown in Figure 8.28. On the other hand, machining of vertical and horizontal plains, simultaneously could be secured in this setup by replacing the boring tool in the vertical spindle by a face milling cutter. NC milling machines may have from two to i ve axes under tape control. NC milling machines can do some of the work normally performed on NC drilling machines such as drilling, boring, and tapping.
3. NC turning machines. Lathes are primarily used for producing cylindrical shapes in addition to cutting tapers, boring, drilling, and thread cutting. NC lathes are equipped with either straight-cut or continuous-path control systems. Most of NC lathes produced today are equipped with continuous-path control and circular interpolation. They are capable of tool offset so that the machine operator can make i ne adjustments in the cutting tool location to achieve the required part size. Figure 8.29 shows a typical NC turning machine.
4. NC machining centers. Machining centers perform a wide range of operations that include milling, drilling, boring, tapping, countersinking, facing, spot facing, and proifiling. Machining centers are able to change the cutting tools automatically, which allow most of the machine time to be devoted to the cutting operation. Most NC machining centers have three axes. In a four-axes system, the fourth axis is used to rotate the table, which allows for the machining of four sides of a part. In many cases, it is possible to machine a part completely without removing it from the machine. Figure 8.30 shows a typical machining center.
5. NC turning centers. These machines combine the features of bar-type, chucking-type, and turret lathes. They are built with four axes of control and are also equipped with continuous-path NC systems with circular interpolation. Their design may include a slanted or vertical bed rather than the horizontal one normally used with conventional center lathes. The capabilities of turning centers can be extended by providing two turrets such that two tools can cut simultaneously. Power-driven tool holders (that rotate when the WP is stationary) permit milling of l ats, keyways, and slots in addition to the drilling of holes offset from the machine axis. Figure 8.31 shows a typical turning center. The use of tooling magazines extends the range of tooling that may be used as shown in Figure 8.32.