CNC milling machines are an upgraded version of milling machines of the conventional type. These machines are more modern and versatile, offer major benefits for machining shops and speed up production processes. What are the parts of this machine? What is the head of a CNC milling machine like?
Differences between CNC and conventional milling machines
A computer numerical control (CNC) milling machine is quite similar to a conventional one, the difference being that it needs minimal intervention from an operator: in other words, it can work automatically thanks to the machine's computer. In fact, special kits are now available that can convert a conventional milling machine to CNC.
Given the strong similarities with the traditional milling machine, both types share the same moving parts:
- Table
- Head
- Spindle
- Cross and longitudinal slides
However, CNC milling machines are operated by a computer in the control panel, whereas conventional milling machines are operated by levers. This computer is, in fact, the most important part of the machine. Computer numerical control (CNC) allows the various parts (spindle, slides, table, CNC milling head and so on) to operate automatically. Thanks to CNC, the milling machine can be programmed so that the computer tells each part of the machine what to do.
For example, depending on the design of the part, the CNC milling machine's head can reach any area of the workpiece, which means the machine can produce parts that are very small and have complex designs. It also allows series production. That is why CNC milling machines are known for improving productivity and for being highly accurate, fast, versatile and safe, and above all for their repeatability and the reduction and optimisation of waste (swarf).
Parts of a CNC milling machine
As mentioned, CNC milling machines and conventional milling machines have the same moving parts. However, these milling machines also include components specific to CNC. The parts of a computer numerically controlled milling machine are:
- Column
- Milling cutter
- Milling table
- CNC milling head
- Control panel/computer
- Workpiece
- Hoses for the coolant
- Travel axes and additional axes
The CNC milling head
One of the most important parts of the milling machine is the head, which rotates to machine the part. On CNC milling machines, the head can be swivelled and has a built-in spindle motor, making the work much faster and more accurate. And because the process is automated, the computer tells the head which tool to use.
A milling machine can carry out multiple machining processes, including drilling and various types of milling. For example, to shape a part, the CNC milling head will use a milling cutter. The milling cutter is the most widely used cutting tool; thanks to the movement of the machine's slides, it can reach the surface of the part and remove chips until the part has been profiled. What if the part needs to be drilled? Thanks to CNC, the head knows that it should not use a milling cutter but a drill. Depending on the model and features of the machine, the change from cutter to drill can take just seconds, and the machine never stops working.
The travel axes
Every machine tool works on a Cartesian plane, which defines the types of movement the table can make with the workpiece clamped on it. CNC milling machines can move along up to five different axes. The main axes of the machine are X, Y and Z, while the additional axes are A and B. It should be noted that not all CNC milling machines can move along these axes; it all depends on the machine model.
The axes of a CNC milling machine are:
- X axis. This axis is horizontal and parallel to the workpiece. It is also associated with the longitudinal movement of the worktable.
- Y axis. It provides movement in the horizontal plane and is said to be transverse to the milling table.
- Z axis. The milling cutter is mounted on this axis, which, as it carries the cutting tool, has enough power to perform the machining. This axis can take up different positions depending on the CNC milling head. It is associated with the vertical movement of the head.
- Additional axes A and B. These allow the part to be placed in any position, giving the CNC milling head access to the part from any angle.