Speed Function
The spindle speed is normally specified using S word address. It can be specified in any of the two ways : either direct RPM, or in constant surface speed in m/min or ft/min using the following G-codes :
- G96 Surface speed in m/min or feet/min
- G97 Speed in rev/min
The default mode is generally G96. When G97 is used, the controller will continually adjust the spindle speed depending upon the X-axis coordinate in that particular block. This would be useful in turning, since the cutting speed is controlled by the diameter of the rotating workpiece rather than the cutting tool dimension as in the case of a machining centre. For example, when taper turning, facing or multiple step turning, all can use the same S word address without change. This provides uniform surface finish all along the workpiece surface.
Sometimes there is a possibility that the spindle speed may reach very high values when the workpiece diameter approaches zero, such as in the case of facing. In such cases an upper limit to the spindle speed can be programmed using a G50 code in the beginning of the program.
N020 G50 S4500 maximum spindle rpm is 4500