In the engineering industry many of the machines that were once manually operated are now operated by computers. Handles, levers, wheels and other types of manually operated machine components and parts have been replaced by automation in one form or another.
The manual operation of some types of precision engineering machine such as the lathe or milling machine are very often controlled by computer or numerically controlled. Numerical control or NC, or computer numerical control CNC refers to the automation of machine tools which are operated by programmed commands that are encoded on a storage medium.
NC machines were first built in the 1940s and were programmed by using paper tape with holes punched into it at specific points. These early systems were soon overtaken with the augmentation of analogue and digital computers.
In CNC milling and turning, end to end component design is automated using CAD/CAM programs. The program is put into the lathe or milling machine and the machine is then ready for production. Some machined components will generally require a number of different tooling applications such as drilling, reaming and tapping etc, and most modern machines will combine tools within a single cell. This cell will move or rotate to apply the required tooling application, and this will also be controlled by the CNC system.
With todays modern and complex machines, the machined part or workpiece can be moved from machine to machine automatically with the use of computer controlled robots, or human intervention, but in either case the steps needed to produce any part is highly automated and the finished part will closely match the CAD design.
A lathe is a machine for revolving a piece of material so as to enable a cutting tool to shape it into a component of circular cross section, or to perform a screw cutting operation. Lathes which are among the most important machine tools vary widely in design. The workpiece is given a rotational motion and the material is cut away by a tool that is given an appropriate combination of linear (axial and radial) movements.
Milling is a machining operation in which a workpiece is given the desired shape by the action of a rotating cutter, while the workpiece performs linear movements. In its simplest form the milling cutter is a circular disc whose rim is provided with specially shaped teeth (cutting edges). The cutters are of many different kinds and shapes. The work is fed against the teeth of the cutter, while the feed motion is longitudinal, transverse or vertical, depending on the type of milling machine and the nature of the work. Milling machines are of the horizontal or vertical type.
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