The milling machine is a machine tool used for metal cutting and has been widely used in machining workshops and factories since the Industrial Revolution. Its defining feature is the rotary motion of its cutting tool, the milling cutter, which has several cutting edges. Today, in addition to conventional models, the CNC universal milling machine is also available on the market.
What are milling machines?
Milling machines are used to machine parts in a range of materials by metal cutting. They are very versatile, thanks both to the large number of operations they can perform and to the materials they accept. A milling machine can work wood, steel, non-ferrous metals, iron and synthetic materials, and it can handle different surfaces, whether flat, curved, toothed, slotted and so on. Parts machined on these machines can also undergo roughing and finishing.
What is a milling machine and how does it work? Conventional milling machines and CNC milling machines do not differ greatly from one another. Broadly speaking, a milling machine is a machine tool equipped with a cutting tool called a milling cutter; the cutter has cutting edges or lips that rotate, removing excess material from the surface of a part.
It was in the early nineteenth century that conventional milling machines were invented. Over the years they adapted to new technologies and to the needs of the sector until they became indispensable in every workshop. With the invention of computer numerical control, or CNC, conventional milling machines were updated, and today there are models that work automatically with the help of a computer.
There are different types of milling machine in industry, and each follows specific processes. The conventional universal milling machine has a main spindle used to mount horizontal tool arbors. It also has a head that couples to this spindle and allows the machine to work as a vertical milling machine. In other words, with the right tools a universal milling machine can easily be converted to vertical milling. On this type of machine, the ram or sliding overarm can move backwards and forwards along guideways.
Features of the CNC universal milling machine
The CNC universal milling machine stands out for the wide variety of machining operations it can perform, but also for the flexibility it brings to manufacturing processes. These machines have also achieved programmable automation of production, and they were designed for high-volume production of simple parts or medium to low volumes of more complex parts. Thanks to computer numerical control, milling machines can switch from one part model to another using advanced programs and tools.
On the CNC universal milling machine, as on other machines using this technology, the CNC unit is controlled by an alphanumeric program, that is, one that uses numbers, letters and other symbols. These include the G and M codes (preparatory movements and cycles, and miscellaneous functions, respectively). These characters are encoded in a suitable language for defining a program of instructions to carry out specific tasks. If the machine needs to switch between programs, it knows what changes to make; these include changing the program but also the tools. For series production, machining workshops and factories can add robotic arms for loading.
The most advanced universal milling machines have electronic readout systems that show the positions of the tools relative to the coordinate system. This readout system makes it easy to read the travel dimensions.
It is worth noting that the alphanumeric programming language of a universal milling machine can vary. Many milling machines use the international standard ISO language, but they may also use Heidenhain, Fagor or Siemens.
Advantages of CNC milling
CNC milling machines run on programming software that allows (and requires) the part to be designed on computers; once the design has been completed on a computer using a CAD program, it is translated into the CNC's alphanumeric language. The operator can program the machine by selecting the cutting parameters required for the part. When the machine starts, the milling machine's computer knows what it has to do and tells the cutting tools which movements to follow and at what feed rate, depth and pass.
This is, without doubt, the main advantage of the CNC universal milling machine: automation. The machine requires minimal operator intervention; the operator only needs to carry out the correct programming. In fact, a single operator can supervise several CNC machines at the same time. CNC milling machines also make machining far more precise than with conventional tools. And that is not all: depending on the number of axes the machine has, the CNC milling head can reach different angles of the workpiece.
Finally, these machine tools optimise production, which helps cut cycle times and lead times and, of course, costs as well.