What type of movement increases the spindle speed, as indicated by G97?

The correct choice pertains to the programming command G97, which is used in CNC machining to set the spindle speed in revolutions per minute (RPM) for a given operation. When G97 is invoked, it instructs the CNC machine to operate in a mode where the spindle speed is defined directly by the operator. This is crucial when machining operations require a specific speed for optimal cutting performance, ensuring the tool can effectively engage with the material without causing damage or excessive wear.

Choosing the RPM setting reflects an understanding of how spindle speed is crucial in machining operations, as it allows for adjustments based on the material being worked and the type of operation being performed. This command is particularly meaningful in context because the spindle speed is paramount to achieve desired outcomes such as surface finish and tool life.

In contrast, the other options do not relate directly to setting spindle speed. Linear movement pertains to how the tool moves in straight paths, circular interpolation is about the movement along a circular path, and tool change refers to the process of swapping out cutting tools rather than adjusting their rotational speed. Each of these has its own relevance in CNC programming, but they do not have the same direct impact on spindle speed as the RPM setting indicated by G97.