Chapter List

Part Overview

INTRODUCTION TO CNC

Numerical control (NC) is the operation of a machine tool by a series of coded instructions consisting of numbers, letters of the alphabet, and symbols that the machine control unit (MCU) can understand. These instructions are converted into electrical pulses of current that the machine's motors and controls follow to carry out machining operations on a workpiece. The numbers, letters, and symbols are coded instructions that refer to specific distances, positions, functions, or motions, which the machine tool can understand as it machines the workpiece.

HISTORY

A form of NC was used in the early days of the industrial revolution, as early as 1725, when knitting machines in England used punched cards to form various patterns in cloth. Even earlier than this, rotating drums with prepositioned pins were used to control the chimes in European cathedrals and some American churches. In 1863, the first player piano was patented; it used punched paper rolls, through which air passed to control the order in which the keys were played automatically, Fig. 1-2.

The principle of mass production (interchangeable manufacture), developed by Eli Whitney, transferred many operations and functions originally performed by skilled artisans to the machine tool. As better and more precise machine tools were developed, the system of interchangeable manufacture was quickly adopted by industry in order to produce large quantities of identical parts. In the second half of the nineteenth century, a wide range of...