TABLE OF CONTENTS The three reference points available for CNC programming must be harmonized to work together correctly. Having the reference points for the part ( i.e., program zero) and the cutting tool ( i.e., tool tip) available, there has to be some means to associate them together, to fit them together. There must be some means to tell the control system exactly where each tool is physically located, within the machine work area, before it can be used. The oldest method to do all this is to register the current position of the tool into the control system memory, through the program. This method required a command called the Position Register.
The preparatory command for the tool position register is G92 for machining centers and G50 for lathes:
| G92 | Position register command (used in milling) |
| G50 | Position register command (used in turning) |
Some CNC lathes also use G92 command, but lathes supplied with Fanuc and similar controls normally use G50 command instead. In practical applications, both G92 and G50 commands have identical meaning and the following discussion applies to both commands equally. In the first part of this chapter, the focus will be on milling applications using G92 command, lathe applications using G50 command will be explained later.
In modern CNC programming, both position register commands were replaced by a much more sophisticated and flexible feature called the Work Offsets (G54 to G59), described in Chapter 18, and the Tool Length...
