CNC Milling is a cutting process in which material is removed from a block or a casting by a rotating tool. In CNC Milling the cutting tool is moved in all three dimensions to achieve the desired part shape. In CNC Milling the cutting tool usually rotates about an axis that is perpendicular to the table that holds the material to be cut. Milling machines are often classed in two basic forms, horizontal and vertical, which refer to the orientation of the main spindle. Both types range in size from small, bench-mounted devices to room-sized machines.
A milling machine looks somewhat like a drill press at first glance. Unlike a drill press , which holds the work piece stationary as the drill moves axially to penetrate the material, milling machines also move the work piece radially against the rotating milling cutter , which cuts on its sides as well as its tip. Work piece and cutter movement are precisely controlled to less than 0.001 in (0.025 mm), usually by means of precision ground slides and lead screws or analogous technology. Milling machines may be manually operated, mechanically automated, or digitally automated via computer numerical control. Additionally, the material can be turned to various orientations in the middle of the process and cutting tools of various shapes can be used. Material is usually removed by both the end and the side of the cutting tool.
Milling machines can perform a vast number of operations, from simple (e.g., slot and keyway cutting, planing, drilling) to complex (e.g., contouring, die-sinking). Cutting fluid is often pumped to the cutting site to cool and lubricate the cut and to wash away the resulting shavings and clippings of metal.
Examples of CNC milled parts include engine components, mold tooling, complex mechanisms, and enclosures.
CNC Milling has several advantages over other manufacturing processes: