TABLE OF CONTENTS Feedrate is the closest programming companion to the spindle function. While the spindle function controls the spindle speed and the spindle rotation direction, feedrate controls how fast the tool will move, usually to remove excessive material (stock). In this handbook, the rapid positioning, sometimes called a rapid motion or rapid traverse motion, is not considered a true feedrate and will be described separately, in Chapter 20.
| Note | Cutting feedrate is the speed at which the cutting tool removes the material by cutting action. |
The cutting action may be a rotary motion of the tool (drilling and milling, for example), the rotary motion of the part (lathe operations), or other action (flame cutting, laser cutting, water jet, electric discharge etc.). The feedrate function is used in the CNC program to select the feedrate value, suitable for the desired action.
Two feedrate types are used in CNC programming:
Feedrate per minute
Feedrate per revolution
The most common types of machines, CNC machining centers and lathes, can be programmed in either feedrate mode. In practice, it is much more common to use the feedrate per minute on machining centers and the feedrate per revolution on the lathes.
There is a significant difference in G codes used for machining centers and lathes.
| FEEDRATE | Milling | Turning Group A | Turning Group B | Turning Group C |
|---|---|---|---|---|
| Per minute | G94 | G98 | G94 | G94 |
| Per revolution | G95 | G99 | G95 | G95 |
| Note | The G code Group A is the most commonly... |
