Five-axis machines represent the pinnacle of CNC design, and they are able to machine solid shapes of unprecedented complexity. The two main application categories for five-axis machining are conventional machining of tilted surfaces and the machining of complex 3D shapes. In both cases, the workflow needed to create five-axis programs has been simplified over the years, but still requires good training to master. It is, however, possible to train operators quickly and simply to perform a limited set of tasks successfully and efficiently.
Five-Axis machine layouts
Like most CNC machining centres, five-axis machines have three linear axes, and the layout of a 5 axis machine therefore closely resembles that of a 3 axis machine. The two additional axes are rotational, and these are what give the machine its extraordinary versatility. The two axes are typically deployed in two alternative ways:
In the first, the two rotational axes are achieved by using two rotary tables, the first mounted on the machine’s table, and the second attached to the first. This allows the work piece to be rotated in two axes simultaneously.
Alternatively, the rotary axes are incorporated into the machine’s spindle and headstock. In this way, the cutting tool and spindle can be slanted in each rotary axis. Thus the work piece remains stationary, useful for machining large parts or for the growing number of Perth machine shops that offer precision wire cutting.
Both these styles of machine use the same axis convention. For example, when viewing the machining centre from the right side, work piece or the cutting tool while slanted either counter clockwise or clockwise, you get the A-axis. When viewing the machine vertically from the front, work piece or cutting tool while slanted counter clockwise or clockwise, you get the B-axis. Let’s briefly discus the two main applications for five-axis CNC machining:
Machining complicated 3D shapes
The two rotary axes are utilized to keep the cutting tool close, and normal to the surface being worked one. In the early days of five-axis machining, programming a CNC machine for 3D work was almost extremely laborious, and required the geometry of each work piece to be transferred from the design to the computer by keyboard, and errors, leading to stalled runs and possibly to wasted stock, were the order of the day.
Since then CAD/CAM software has improved to the point where the flow from concept through design to production is seamless. Far fewer designs originate on paper, and a piece designed today by an engineer in Finland can be driving a machine in Perth overnight.
Once a design is imported, the programmer’s job is relatively simple. However, there are many machining options available, such as pass rates and cutting path step sizes, to allow for optimum handling of different workpiece material properties.
Traditional machining; tilted surfaces
5 axis machines are not always used for 3D work. Their two rotational axes enable them to machine sloping planes, a frequent requirement that 3 axis machines cannot meet. They can therefore be used for many conventional tasks like milling, boring, reaming, tapping and drilling, where the task axis is not normal to the machine table. Some training is needed to operate the machine in this mode, but far less than is required to master its full 3D capability.