What Are the Functions of Computer Numerical Control CNC?

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Read : What is CNC (Computer Numerical Control)? Advantages, Limitations, Applications
Comparison between CNC and DNC - Advantage and functions of DNC


CNC is designed to perform many functions which either difficult or impossible to perform by a NC machine. Some important function of CNC are:
  • Machine Tool Control
  • In-process compensation
  • Improved programming and operating features
  • Diagnostic

Machine Tool Control

Controlling the machine tool is the primary function of a CNC. It includes the conversion of part program instruction into machine tool motions. This conversion is done through a computer interface and servo system.

In-process compensation

It involves the real-time dynamic correction of errors in the machine tools motion during processing. Some features of in-process compensation are listed below
  1. Debugging the problem and adjusting for the error sensed by in-process probes and gauges.
  2. Recalculation of axis positions when inspection probe is locating the reference on work part.
  3. Adaptive control adjustment to the tool speed and feed.
  4. Compute the predicted tool life and select alternative tooling when indicated.
  5. Offset adjustment for tool radius and length.

Improved programming and operating features

The flexibility of soft-wired control of CNC allows the introduction of many convenient programming and operation features. The main features are listed below
  1. Manual data input and editing of part program at machine - it permits the correction and optimization of part program.
  2. Graphic display tool path help to verify the tape.
  3. Support more than one system of units.
  4. Use of specially written subroutine program.
  5. Types of interpolation technique: Cubic, circular and parabolic interpolation.
  6. Large local storage system that having  more than one  program.

Diagnostic

CNC machines are very expensive and complicated. The complexity of machine required well trained and proficient personal for maintenance. The CNC machines are often equipped with the diagnostic capability to assist during the maintenance of system. The diagnostic subsystem has several features. One of the main features is that it identifies the reason for a problem and guide the maintenance personnel so that he/ she can repair the system very quickly.

Second feature that it alerts the imminent failure of certain component, so the maintenance personnel can check/ replace the faulty component during scheduled downtime and thus avoid unplanned downtime.

Third possible function is that when a component fails, the diagnostic subsystem automatically disconnects the faulty component and activate the redundant component. It helps to avoid the further damage to machine and work; repairs can be done without breaking the normal operation.

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