Common machining centers can only move on the three axes of X, Y, and Z, and are also called "3-axis machine tools." 5-axis machining refers to cutting using a machining center that supports 5-axis machining. This type of machining center is also called a "5-axis machine tool" or "5-axis machining center." The advantage of 5-axis is that in the face of complex special-shaped parts, 5-axis machining can omit the very time-consuming production preparation changes on 3-axis machine tools, thereby shortening working hours, and can also perform processing content that 3-axis machine tools cannot complete. So what is the difference between 3-axis machine tools and 5-axis machine tools? First, let's look at their structure. Figure 1-1 shows the appearance of the internal area of 3-axis machine tools and 5-axis machine tools. 3-axis machine tools are composed of a worktable and a spindle that fix the workpiece.
【Figure 1-1】Appearance comparison between 3-axis machine tools and 5-axis machine tools
The spindle can move relative to the table in three directions: left and right (X-axis), front and back (Y-axis), and up and down (Z-axis). The end mill is mounted on the spindle and moves freely in three directions while rotating to cut the workpiece. This allows various shapes to be processed, including 3D processing.
In the structure of a 5-axis machine, in addition to the three axes of X, Y, and Z, two axes of rotation are added. Figure 1-1 shows the structure of a typical cradle-type 5-axis machine. The table can be freely tilted in two directions of rotation: rotation around the X-axis (A-axis) and rotation around the Z-axis (C-axis). Since the mechanism for rotating the A-axis acts like a cradle, it is called a "cradle type".
Sometimes, the spindle side is also equipped with a 1-axis or 2-axis rotation function (so-called 5-axis machine). With such a mechanism, what kind of processing can a 5-axis machine actually complete? Let's take a look at the schematic diagram of the specific action. Please see Figure 1-2.
【Figure 1-2】 Schematic diagram of the operation of a 5-axis machine tool
First, as shown in (1), the workpiece is placed directly on the workbench for processing, and the top is facing the spindle. The red surface is just within the cutting range. Then, if the A axis is tilted 90 degrees, it becomes state (2). The surface that cannot be cut in state (1) now faces the spindle and can be cut.
Then, the C axis is tilted 90 degrees, and it becomes state (3), and the next surface can be processed. Continue to rotate the C axis, and other surfaces can be processed in sequence. In other words, after the workpiece is installed, all surfaces except the bottom can be processed. This can shorten processing time and improve processing accuracy without changing production preparation.
Of course, 5-axis machine tools can not only rotate in 90-degree increments as shown in Figure 1-2. The A axis and C axis can be freely set to any angle, and the A axis and C axis can rotate independently. In addition, the A axis, C axis and the five axes of X, Y, and Z can move dynamically at the same time. The conventional use of 5-axis machine tools is to tilt the A axis or C axis to a certain angle for processing, and then tilt it to the next angle for processing. When the spindle moves, the rotating axis is in a stopped state. This type of machining method is called "fixed 5-axis machining" or "indexed 5-axis machining".
On the other hand, the machining method in which all axes, including the rotating axis, move simultaneously is called "synchronous 5-axis machining". Shapes such as impellers must be machined using synchronous 5-axis machining.
In addition, some 5-axis machines also have the ability to rotate the C axis at high speed, allowing turning like a lathe.
【Figure 1-3】 Features of 5-axis machine tools
