One of today's most advanced machining techniques is 5-axis machining. This type of process makes it possible to machine parts of different shapes and sizes which, because of their characteristics, cannot be worked on other machine tools. How does 5-axis CNC work? Which machine tools offer it?
What is 5-axis machining?
Before looking at how 5-axis CNC machining works, it is worth understanding this revolutionary technique, which brings nothing but advantages to industry. This type of machining takes its name from the number of directions in which a machine's cutting tool can move. As you know, conventional machine tools can move in different directions, but only within certain limited planes: the lathe, for example, moves only in the X and Z planes, while the milling machine works along the X, Y and Z axes. 5-axis machining adds two more: A and B.
The A and B axes are actually rotary movements that allow the cutting tool to approach the workpiece from any angle and direction. In fact, all machines, even those without 5 axes, can reach any point on the workpiece; the difference is that the part has to be repositioned manually, which is not the case with a CNC machine.
Having a 5-axis machine with CNC brings nothing but benefits for machine shops. While on a conventional machine the operator has to reposition the part, the CNC machine does so automatically by means of the A and B axes, depending on the operation to be performed on the part; this cuts production times.
In short, 5-axis CNC machining is the process that, in a single operation and without stopping the machine or repositioning the workpiece, can machine all five faces of the part. 5-axis machining is regarded as one of the most advanced and complex techniques in the machining industry. It is a metal-cutting process, and the movements can be performed by either the worktable or the spindle head.
Multi-axis machining
It is important not to confuse the different types of multi-axis machining. Although both are among the most advanced techniques and both involve five axes, it is essential to be able to tell them apart. The types of multi-axis machining are:
- 3+2 machining. This type also includes the A and B axes, but they remain fixed, unlike the X, Y and Z axes, which move simultaneously. The A and B axes can move, but only when switching from one operation to the next.
- 5-axis machining. As mentioned above, all 5 axes move simultaneously.
How 5-axis CNC works: machining centres
Not all CNC machines can machine on 5 axes; only specific machines known as machining centres can do so. These machines work automatically, can carry out multiple machining operations and are driven by computer numerical control (CNC). They require minimal human intervention and use rotating cutting tools, chiefly drills and milling cutters.
So how does 5-axis CNC work on a machining centre? These machine tools can carry out automated processes thanks to CNC. Like all other computer numerically controlled machines, machining centres need additional software for programming before they can machine a part. Before the workpiece is placed on the machine table, it must have been designed on separate computers using CAD (computer-aided design) and CAM (computer-aided manufacturing) software. Once the part has been designed externally, the design must be converted into alphanumeric CNC code and loaded into the machine tool's computer.
Once programming is complete (it can be done automatically or manually), the machining centre can start work. It is precisely the design loaded into the computer that tells the machine which cutting tools to use and how to position the part.
How the axes move
One of the features of a machining centre is that it can machine all faces of a part in one go. This is possible thanks to its 5 axes. The first three correspond to the Cartesian system: X, Y and Z. The fourth and fifth axes are A and B, respectively. The A axis is used to control the rotation of the part about any of the axes; it is ideal for machining cylindrical parts.
The B axis, for its part, provides the rotation mechanism for all axes simultaneously. The fifth axis allows combinations of rotations that give greater freedom of movement; in addition, the B axis enables a perpendicular movement about the axis while the part tilts perpendicular to it.