Saturday, 11 October 2014

CNC SYSTEM

The modem CNC system, but not the old NC system, uses an internal micro processor (i.e., a
computer). This computer contains memory registers storing a variety of routines that are
capable of manipulating logical functions.
That means the part programmer or the machine operator can change the program on the control
itself (at the machine), with instantaneous results. This flexibility is the  greatest advantage of the
CNC systems and probably the key element that contributed to such a wide use of the technology
in modern manufacturing. The CNC programs and the logical functions are stored on special
computer chips, as software instructions rather than used by the hardware connections, such as
wires, that control the logical functions.
In contrast to the NC system, the CNC system is synonymous with the term 'Softwired' (because
most of their control functions are implemented by the control software programs).All numerical
control machines manufactured since the seventies are of CNC type.
The control signals in CNC systems are in the form of binary words. Each word contains a fixed
number of bits, 32 bits or 64 bits are commonly used. Each bit of data produces one BLU motion
in the controlled axis.
Theoretically a 32 -bit word could represent one of up to 2 raise to power 32 = 4,294,967,296 different axial positions. If the system resolution is, for example, BLU = 0.0001
in., this number can represent up to 429,969 in. possible motions, which is more than enough for
all types of applications.
When describing a particular subject that relates to the numerical control technology, it is
customary to use either the term NC or CNC. Keep in mind that NC can also mean CNC in
everyday talk, but CNC can never refer to the older technology.

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