TABLE OF CONTENTS The address M in a CNC program identifies a miscellaneous function, sometimes called a machine function. Not all miscellaneous functions are related to the operation of a CNC machine - quite a few are related to the processing of the program itself. The more suitable term miscellaneous functions is used throughout this handbook.
Within the structure of a CNC program, programmers often need some means of activating certain aspects of the machine operation or controlling the program flow. Without the availability of such means, the program would be incomplete and impossible to run. First, let's look at the miscellaneous functions relating to the operation of the machine-the true machine functions.
Various physical operations of the CNC machine must be controlled by the program, to ensure fully automated machining. These functions generally use the M address and include the following operations:
| ? Spindle rotation | CW or CCW |
| ? Gear range change | Low / Medium / High |
| ? Automatic tool change | ATC |
| ? Automatic pallet change | APC |
| ? Coolant operation | ON or OFF |
| ? Tailstock or quill motion | IN or OUT |
These operations vary between machines, due to the different designs by various machine manufacturers. A machine design, from the engineering point of view, is based on a certain primary machining application. A CNC milling machine will require different functions related to the machine than a CNC machining center or a CNC lathe. A numerically controlled...
