CNC machining is the modern replacement of analog devices, in which movement was dictated by turning wheels, levers and cams controlled by a machinist. This earlier process utilized simple scales and patterns that resulted in a lack of uniformity and low precision.

In comparison, CNC machines are digitally controlled using numerical coordinates defining their continuous movement. Digital controls ensure that cutting is uniform and repeatable, resulting in consistent high-quality milled parts. Though CNC machines can be used in combination with other technologies, for the purposes of this article, we will focus on CNC use in subtractive manufacturing processes where computerized controls are used with machine tools to remove layers of material from a stock piece.

ZLD has been using CNC machines to build plastic injection tooling, silicone molding tooling and fixtures; to fabricate metal components; and to prototype plastic components prior to making production tooling.