CNC Machining is that processes that a piece of raw material is cut into a desired final shape and sized by a controlled material-removal process. The processes that have this common theme, controlled material removal, are today collectively known as subtractive manufacturing, in distinction from processes of controlled material addition, which are known as additive manufacturing. Exactly what the “controlled” part of the definition implies can vary, but it almost always implies the use of machine tools (in addition to just power tools and hand tools).
Machining is a part of the production of metal parts, but it can also be used on other materials such as wood, plastic, ceramic, and composites. Much of modern day machining is carried out by computer numerical control (CNC), in which computers are used to control the movement and operation of the mills, lathes, and other cutting machines.
Computer Numeric Control (CNC) is the automation of machine tools that are operated by precisely programmed commands encoded on a storage medium (computer command module, usually located on the device), as opposed to controlled manually by hand wheels or levers, or mechanically automated by cams alone. Most NC today is computerized numerical control (CNC), in which computers play an integral part of the control.
In modern CNC machining systems, end-to-end component design is highly automated by using computer-aided design (CAD) or computer-aided manufacturing (CAM) programs. The programs produce a computer file, interpreted to extract the commands needed to operate a particular machine by use of a post processor, and then loaded into the CNC machines for production. Since any particular component might require the use of a number of different tools – drills, saws, etc. – modern machines often combine multiple tools into a single “cell”. In other installations, a number of different machines are used with an external controller and human or robotic operators that move the component from machine to machine. In either case, the series of steps needed to produce any part is highly automated and produces a part that closely matches the original CAD design.
Machining can be dividied into 4 categoiries: drilling, turning, milling, grinding and chip formation.