TABLE OF CONTENTS Addresses in a CNC program that relate to the tool position at a given moment are called the coordinate words. Coordinate words always have a dimensional value, using currently selected units - metric or imperial. Typical coordinate words are X, Y, Z, I, J, K, R, etc. They are the basis of all dimensions in CNC programs. Tens, hundreds, even thousands of calculations may have to be made to develop a program that will do what it is intended to do - to accurately machine a complete part.
Dimensional entries in a program assume two attributes:
| Imperial or Metric |
| Absolute or Incremental |
Unit of dimensions in a program can be one of two kinds - metric or imperial. The reference of dimensions can be either absolute or incremental.
Fractional values, for example 1/8, are not allowed in a CNC program and have to be converted to their decimal equivalent. In metric format, millimeters and meters are used as units, in imperial format it is inches and feet that form the basis of units. Regardless of format selected, the number of programmed decimal places can be controlled, suppression of leading and trailing zeros can be set and decimal point can be programed or omitted, as is applicable to a particular CNC system.
Drawing dimensions can be used in a program in either metric or imperial
