Computer numerical controlled (CNC) machine tools that have revolutionized the design process. The NC part of CNC refers to numerical control (refers to the automation of machine tools that are operated by conceptually programmed commands programmed on various storage mediums) early models in the 1940s and '50s, based on existing tools that were modified with motors that moved the controls to follow points fed into the system on paper tape.
In modern CNC systems, end-to-end component design is greatly automated using CAD/CAM programs. The programs produce a computer file that is interpreted to extract the instructions needed to operate a particular machine, and then loaded into the CNC machines for fabrication. Components might require the use of a number of different tools—drills, saws, mills, and lathes etc.—current machines often merge multiple tools into a single "cell". A number of different machines are used with an external controller and human or robotic operators that move the component from machine to machine. The complex chain of steps needed to manufacture any part is highly automated and produces a part that closely matches the original CAD design.