Numerical Control Programming
Chapter 1
What Is Numerical Control & What Does It Do?

Numerical control (N/C) is the process of "feeding" a set of sequenced instructions (consisting of alpha and numeric characters)--the program--into a specially designed programmable controller and then using the controller to direct the motions of a machine tool (such as a milling machine, lathe, or flame cutter.)

The program directs the cutter to

  1. follow a predetermined path
  2. at a specific spindle speed and
  3. feedrate that will result in the production of the desired geometric shape in a workpiece.

N/C controllers are designed to control the movement of a cutter along the machine's axes of motion, the rotation of the spindle, the changing of cutting tools, and many miscellaneous functions such as turning the coolant on and off. In addition to producing the external geometry of a workpiece, internal geometries such as pockets and recesses can be produced, holes can be drilled, reamed, bored, countersunk, and/or tapped. Machine tools that are equipped with such specialized programmable controllers are called "numerical control machines".

An industrial robot is actually a form of an N/C machine, in that its motion is controlled by a controller very similar in function to that of an N/C machine (although it may be programmed differently). A robot is nothing more than an articulated mechanical arm that is controlled by a special programmable controller. The motion of its mechanical arm, to which a device called an "end effector" is attached, can be used to feed a workpiece into a machine, move a spot welder to a series of locations on an automobile body, or move a paint spray gun along a complex path that will assure complete and uniform coverage.

Conversely, an N/C machine is a form of a robot, in that it can be programmed to perform a series of operations and run itself. Both can be quickly reprogrammed to perform new tasks. N/C machines, however, are far more common in industry than are robots. It is probable that robots will never become more numerous than N/C metalworking machine tools.

Many other kinds of manufacturing equipment and manufacturing processes are controlled by other types of programmable controllers. For example, a heat-treating furnace can be equipped with such a controller that will monitor temperature and the furnace's atmospheric oxygen, nitrogen, and carbon and make automatic changes to maintain these parameters within very narrow limits.

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Updated Jan. 9, 2002
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