What is CNC Technology?
What is CNC Technology?
CNC technology was developed in the United States in the 1950’s for the US Air Force by metalworking machine tool builders. It was a major advance in the ability of machines to faithfully reproduce complex part machining steps more accurately without human intervention or variability.
CNC stands for Computer Numerically Controlled. CNC always refers to how a machine operates, that is, its basic method of controlling movement. Put another way, a CNC machine uses a stream of digital information (code) from a computer to move motors and other positioning systems in order to guide a spindle over raw material.
A CNC machine uses mathematics and coordinate systems to understand and process information about what to move, to where, and how fast. Most CNC machines are able to move in three controlled directions at once. These directions are called axes (pronounced ax-ees). The axes are given simple names such as X, Y and Z (based on the Cartesian Coordinate System). The X axis is always the longest distance a machine or a part of a machine must travel. X may be the movement from front to back, Y the movement from left to right, and the Z is almost always vertical movement (normally the spindle’s positioning movement up and down).
A CNC machine must be able to communicate with itself to operate. A computer numeric control unit sends position commands to motors. The motors must talk back to the control that, indeed, they have acted correctly to move the machine a given distance. The ability of CNC machines to move in three (or more) directions at once allows them to create almost any desired pattern or shape. All of this processing happens very fast.
Advantages of CNC Production
Lower Labor Requirements
A CNC machine can eliminate several processing steps. Where once a sheet of material would move from one production machine step to another, the CNC machine can do more operations in one set-up. Full sheets of material may be used, rather than “pre-blanking” on a saw or other machine. One operator can do the jobs of several people.
CNC machines require good operators to make good parts. But once the company’s part programming information (knowledge) is contained in electronic files, the craftsmanship of the company resides in the machine, not in human operators. Training for new employees relates to how the machine operates and what the company expects for finished part quality, not in teaching the operator information about basic trade skills.
Better Production Parts
No human could hope to control the movements of a machine as precisely as a CNC. These machines work with very small units of measure. A CNC is able to drill a hole at one end of the worktable, move to the far corner and return to make the same hole again with only a few ten-thousandths of an inch error. The accuracy of a CNC can be explained this way: take a hair off your head and slice it the long way six times. The sliver you have left is about the margin of error with the machine.
A CNC may also be programmed to allow for wood grain, material type and special cutter requirements. Humans are not able to balance all of these factors in a repeated way over extended periods of time. Machines may work two or three shifts per day without shut-down. The only limiting factors in CNC production relate to material availability and cutter wear.
CNC machines used to be associated with high-volume production due to the time involved in machine programming. New computer technologies, along with software advances, now allow easy programming of CNC machines for custom or one-of parts. In fact, the ability of a CNC to accept precise mathematic information to create custom parts reduces production costs by reducing potential errors.
Better, Safer Production
A CNC machine does not require any positioning of the spindle to be made by hand during production. The operator’s main job is to monitor the machining process and make any needed corrections. Most machines feature at least one emergency stop button to instantly halt production should a part processing error occur.