OVERVIEW

The majority of CNC programs will be programs for a single job - a job that is relative to a specific machine available in the shop. Such a particular job will have its unique characteristics, its special requirements as well as its own tool path. The tool path is the most important of all the features of a CNC program.

It is the CNC programmer's main responsibility to develop a functional tool path for any given job, without errors and in the most efficient way. The tool path development is very important, because it represents a machining pattern unique to the job at hand. In most programming jobs, this machining pattern is executed for the given job only and is irrelevant to any other CNC program. Often, programmers encounter opportunities, where an existing machining pattern can be used for many new jobs. This discovery will encourage development of the programs more efficiently and produce CNC programs for many additional applications and without errors.

The programming technique that addresses this issue is known as the Translation of a Machining Pattern or, more commonly, a Datum Shift. The most typical example of this technique is a temporary change of the program reference point (program zero) from the original position to a new position, so called work shift. Other programming techniques include Mirror Image, described in the next chapter, Coordinate Rotation and Scaling Function, described in the chapters that follow.

This chapter describes in detail the...