What is the purpose of the G96 code in CNC machining?

The G96 code is used in CNC machining to specify that the machine should operate with constant surface speed (CSS) during the turning process. When G96 is set, the CNC controls the spindle speed automatically in response to the diameter of the workpiece being machined. This allows for optimal cutting conditions by maintaining a constant speed at the cutting edge, regardless of the diameter as work progresses, which can improve tool life and surface finish.

Operating with constant surface speed is especially beneficial in turning applications because it allows for higher cutting speeds on larger diameters while reducing speed on smaller diameters, thus allowing the cutting tool to perform efficiently throughout the entire machining process. This gives it an advantage over simply setting a fixed spindle speed, which would not adapt to changing diameter sizes during the cut.

The other options do not align with the specific function of G96, as spindle speed setting, feed rate specification, and tool compensation are managed by different codes or parameters within CNC programming.