Computer numerical control (CNC) machining is a manufacturing process that uses computers to automate various machine tools. The CNC machining process typically begins with a computer aided design (CAD) program, which can be used to create specifications for a component, part, or other manufactured product. This design is then turned into a series of numerical values that a CNC machine may use to move and operate a variety of tools. A part may be completed in one CNC machine or it may be moved manually or through robotic means between several workstations with different tools. CNC machining can include tools such as drills, presses, and saws.
Prior to the introduction of CNC machining, devices were typically set and operated by hand. An operator had to use a variety of dials to position a workpiece and operate the tool, though some mechanical automation was possible through the use of cams. The genesis of numerical control (NC) machining was in the 1940s, when punch card calculators were used to locate cuts that were then made by hand. Later processes also used punched tape as a data input method, and the holes in the cards would be interpreted as numerical values for the machine to make automatic cuts.
Modern systems use computer terminals to program and interface with the machines and can work with virtually any type of machining tool. Tape is still used in many CNC machining processes, though the original paper material has been largely replaced by sturdier mylar. New systems can also use modern data storage methods and interface with local area networks (LANs), though tape still persists in older machines and for reasons of backward compatibility.
The CNC machining process typically consists of a table that a workpiece can be placed on. These tables often provide two axes of movement to position a part, and the tool itself is a third. Certain setups also include a backgauge, which can add between one and seven additional axes to position a part more precisely.
Some CNC machines only have one tool, whether it is a drill, press, saw, or something else. Others have several different tools in a single cell so that a piece can easily be cut, drilled, and worked on in other ways. The main alternative to this is having several CNC machines hooked together so that a single program can be used to operate each. A piece may be cut on one station before being moved to another for drilling, bending, or other manipulation. This process can be entirely automated or may require a human to move the piece between machines.
