OVERVIEW

Both types of CNC machines, machining centers and lathes, use spindle rotation when removing excessive material from a part. Spindle rotation may be that of the cutting tool (milling) or the part itself (lathes). In both cases, activities of machine spindle and working feedrate of the cutting tool need to be strictly controlled by the program. These CNC machines require instructions that relate to the selection of a suitable speed of machine spindle and a cut-ting feedrate for a given job.

There is a number of ways to control machine spindle and cutting feedrate and they all depend mainly on the type of CNC machine and the current machining application. In this chapter, we look at the spindle control and its programming applications.

SPINDLE FUNCTION

Program command relative to spindle speed is controlled in the CNC system by the address S. Programming format of the S address is usually within the range of 1 to 9999 for standard machines and no decimal point is allowed:

For many high speed CNC machines is not unusual to have spindle speed available up to five digits, in the range of 1 to 99999, within the S address range:

Maximum spindle speed range available in the control must always be greater than the maximum spindle speed range of the machine itself. It is quite typical that virtually all control systems support a much greater range of spindle speeds than the CNC machine...