Milling method
(1) Circumferential milling method: circumferential milling has two milling methods: conventional milling and forward milling. As shown in Figure 5-6a, when the rotation direction of the milling cutter is opposite to the feed direction of the workpiece, it is called conventional milling, and when it is the same, it is called climb milling, as shown in Figure 5-6b. In conventional milling, the cutting thickness gradually increases from zero. The cutting edge of the milling cutter has a blunt circular radius m, which causes the rake angle to be negative when the cutting starts, and the cutter teeth are extruded and slid on the transition surface, which makes the surface of the workpiece produce a serious cold and hard layer, and aggravates the wear of the cutter teeth. In addition, when the instantaneous contact angle is greater than a certain value, the vertical component of the feed force is upward, and there is a tendency to lift the workpiece. During downmilling, the cutting thickness of the cutter teeth starts from the maximum, which avoids the phenomenon of extrusion and gliding; And the vertical component of the feed force is always pressed towards the table, which is conducive to workpiece clamping, which can improve the life of the milling cutter and the quality of the machined surface.
If there is a gap between the lead screw and the nut pair, when the feed force gradually increases, when the friction force exceeds the workbench, the workbench drives the screw rod to move to the left, resulting in uneven feeding, and in serious cases, the milling cutter will collapse. During conventional milling, due to the action of the feed force, the lead screw and the nut transmission surface are always close together, so the milling process is relatively stable.
(2) End milling method When end milling, according to the different installation position of the face milling cutter relative to the workpiece, it can also be divided into conventional milling and climb milling. As shown in Figure 5-7a, the axis of the face milling cutter is located in the center of the milling arc length, and the upper part is equal to the lower part of conventional milling, which is called symmetrical end milling. The conventional milling part in Figure 5-7b is larger than the climb milling part, which is called asymmetric conventional milling. The part in Figure 5-7c that is larger than the part of conventional milling is called asymmetrical side milling. In the figure, the tangent angle 8 and the tangent angle 8, where located on the side of conventional milling is a positive value, and is located on the side of forward milling is a negative value.
Figure 5-6 Conventional milling and climb milling
a) Conventional milling b) Climb milling
Figure 5-7 Climb milling and conventional milling during end milling
a) symmetrical end milling b) asymmetric conventional milling and c) asymmetric climb milling
