1.1. F parameter and Feed management (G93 G94 G95)

The F parameter defines the feed velocity during machining and it is programmed writing the letter F followed by the desired feed value (numeric value with a maximum of 9 significant digits). Programmed after G94 it defines the F velocity in “units” per minute. Example: With linear axes measured in millimeters, F100 means 100 mm/min. With linear axes measured in inches, F100 means 100 in/min. With round axes measured in degrees, F100 means 100 deg/min. G94 is active after reset and it is thus the normal mode if not otherwise specified. Programmed after G95 it defines the feed velocity as “units” per spindle round. “Units” can be millimeters, inches or degrees, depending on the axis type. Programmed after G93 it defines the velocity as the inverse of time (expressed in minutes) necessary to execute the programmed movement. In this case the F value to be programmed is equal to the velocity desired on the trajectory, divided by the length of the trajectory itself: F = Velocity (mm/min or in/min) / Space (mm or inches)

2.2 S parameter and Speed management (G96 G97)

The S parameter defines the spindle rotational speed and is programmed writing the letter S followed by the desired speed value (numeric value with a maximum of 9 significant digits). The S function doesn’t activate the spindle rotation, activated through the auxiliary functions M3 or M4. Programmed after G97 it defines the spindle rotational speed in rpm. G97 is active after reset and it is thus the normal mode if not otherwise specified. Programmed after G96 it sets the mode “ Constant cutting speed ". This is a typical functionality of lathes manufacturer: the spindle rotational speed is computed in such a way that the cutting speed is equal to the programmed S value (expressed in m/min), considering the tool distance from the rotation centre of the spindle. Note on G96 : In order to avoid excessive speed when the distance from spindle center is very small, aside G96 the parameter MS is activated (programmable also before the S value) which sets the maximum spindle rotational speed (in rpm) allowed. The active MS value is that present at the moment of last programmed S: if the parameter MS is newly programmed, the limit doesn't change until a new programming of S value. The tool may jump over the rotation centre: the speed is in every case determined by the absolute value of the distance from spindle center, while the center crossing is limited by the programmed MS. It is possible to program: MS 4000 G96 S100 M3 This programming imposes a cutting speed of 100 m/min. With a maximum speed limit of 4000 rpm.

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