The power of 5-axis machining lies not only in the fact that it can omit the need to change production preparations, but also in the fact that it can precisely control the inclination angle, so that the workpiece can be approached from various angles. The following are the advantages of 5-axis machining.
1. Use 5-axis machining to reduce the time and cost of multi-faceted machining
5-axis machining can not only omit the time to change production preparations when machining hexahedrons. It can also play a huge role in complex shape machining scenarios that must be processed from different angles. Without 5-axis machining, it would take a lot of time and effort to make a dedicated fixture for each inclination angle, which is obviously impractical.
With 5-axis machining, the angle and direction can be freely controlled, and there is no need to use dedicated fixtures, etc. This can significantly reduce the number of production hours and costs of early products.
Let's consider the machining of the slider shown in Figure 3-1. For each of the two inclined surfaces, an open pocket perpendicular to the surface is machined.
Figure 3-1 Tilt block
When machining such an inclined surface using a normal 3-axis machine, the inclined surface must face the spindle, so careful alignment is required. One method is to use a tool such as a bench vise with a tilting function, and another method is to make a special fixture. A bench vise with a tilting function is shown in Figure 3-2. On a 3-axis machining machine, you can use such a bench vise to fix the workpiece and adjust it to the angle required for machining. This has a certain threshold difficulty and consumes effort, and because it is a simulation operation, it will lead to deterioration of machining accuracy.
Figure 3-2 Example of a bench vise with tilt function
Figure 3-3 shows a special jig. By making such a jig and placing it under the workpiece, the inclination of the workpiece can be changed and fixed even on a 3-axis machining center.
Figure 3-3 Schematic diagram of the fixture for tilting the slider (appearance and cross section)
For example, a schematic diagram of fixing is shown in Figure 3-4. With this fixture, a pocket groove can be machined on an inclined surface using a 3-axis machine tool. Of course, in this case, a separate special fixture is also required for the pocket groove on the other inclined surface.
It is not difficult to imagine that this processing method requires a lot of man-hours and manpower.
Figure 3-4 Schematic diagram of machining using a tilted slider
If a 5-axis machine tool is used, these hours are not needed. Simply fix the workpiece on the table, rotate the A-axis and C-axis on the machine tool, and you can start processing immediately.
2. 5-axis machining is to make the tool contact the workpiece at an angle
In 5-axis machining, although it is not particularly concerned, there are some unique advantages to making the workpiece contact the tool at an angle. One advantage is that the tool overhang length can be shortened in some cases. The second advantage is that the part other than the tip of the ball-end mill can also be used to cut the workpiece.
The overhang length is the distance from the tip of the tool to the end face of the shank. It has been explained before that the relationship between the tool diameter (D) and the overhang length (L) should satisfy L/D ≤ 5. If the overhang length is too long, the tool vibration will increase, the machining accuracy will deteriorate, and the surface after cutting will be rough and easy to get dirty.
Let's consider the machining of the part (L-shaped slider) shown in Figure 3-5.
Figure 3-5 L-shaped slider
The inner depth of the L-shaped slider is 120 mm, and the corner radius is R5. If this part is machined using a 3-axis machine tool, the situation shown in Figure 3-6 (1) will occur.
Figure 3-6 Comparison of processing methods of L-shaped sliders
Since the corner radius is R5, a Φ10 ball-end milling cutter is used. The overhang length of the ball-end milling cutter must be increased to ensure that there is no interference between the wall and the tool holder. The overhang length must be at least 120 mm.
In this case, the overhang length (L) 120 mm ÷ tool diameter (D) 10 mm = 12.0. The overhang length is too large for the original L/D ≦ 5. If cutting is started directly, the surface may be rough overall, and sometimes the tool may even be damaged during processing and damage the workpiece.
When machining with a 5-axis machine, the work can be tilted to a convenient angle, so there is no need to worry about the tool holder interfering as shown in Figure 3-6 (2), and the overhang length can be reduced.
This allows the machining of shapes that cannot be machined with a 3-axis machine. Or a smoother surface can be machined by reducing the overhang length.
In addition, the tip speed of a ball-end milling cutter is zero. That is, there is basically no cutting force near the center of rotation. It is forced to press it against the workpiece to cut. If 5-axis machining is used, the workpiece is tilted and placed against the end mill, so that the portion with zero rotation speed can be kept away from the workpiece.
In other words, since the workpiece is cut using the portion with cutting force, the surface is smoother.
