Milling lead method
When programming the machining of face milling, the user must first consider how the cutter cuts into the workpiece. Usually, the milling cutter is simply cut directly into the workpiece (see Figure 6-1), which is usually accompanied by considerable impact noise, which is believed to be due to the thickest chips generated by the milling cutter when the insert exits the cut. Due to the large impact of the insert on the workpiece material, it tends to cause vibrations and create tensile stresses that shorten the tool life.
A better way to feed is to use the arc entry method, that is, the milling cutter arcs into the workpiece without reducing the feed rate and cutting speed (see Figure 6-2). This means that the cutter must be rotated clockwise to ensure that it is machined in a climb milling manner. This results in a thicker-to-thin chip, which reduces vibrations and tensile stresses acting on the tool and transfers more cutting heat into the chip.
By changing the way the milling cutter cuts into the workpiece each time, the tool life can be extended by 1~2 times. To achieve this approach, the toolpath should be programmed with a radius of 1/2 of the cutter diameter and an increased offset distance from the tool to the workpiece. While the arc plunge method is primarily used to improve the way the tool cuts into the workpiece, the same machining principle can be applied to other stages of milling.
For large-area face milling, a common programming method is to have the tool mill one by one along the full length of the workpiece and complete the next cut in the opposite direction (see the left image in Figure 6-3). In order to maintain a constant radial feed and eliminate vibration, it is usually better to use a combination of spiral downcut and arc milling workpiece corners (see Figure 6-3 right). One of the principles of this approach is to keep the cutter as continuous as possible and to keep the same milling method (e.g. climb milling) as much as possible. In the path of the milling cutter, it is necessary to avoid the corner of the right angle and adopt the corner of the arc, as shown in Figure 6-4.
6-1 6-2
6-3
6-4
Similarly, in order to ensure a smooth cut, it is also possible to take a path that bypasses these hollow elements for interruptions and holes in the workpiece (see Figure 6-5). If this hollowness cannot be avoided in the pass path, milling can also be done on the workpiece area with interrupted positions, reducing the recommended feed rate by 50%.
