The appearance of CNC system is very similar to NC system but the way of using the program is different. In a conventional NC system, the punched tape is cycled through the tape reader for each work part in the batch. The machine control unit reads in a block of instructions on the tape executing that block before proceeding to the next block. In CNC, the entire program is entered once and stored in computer memory. The machining cycle for each part is controlled by the program contained in memory rather than from the tape itself. The general configuration of CNC system is shown in Figure 22.2.
Figure 22.2 Components of CNC Systems
Following features are associated with CNC system:
- Storage of more than one program.
- Use of floppy/discs.
- Program editing at the machine tool site.
- Fixed cycles and programming subroutines.
- Interpolation.
- Positioning features for setup.
- Cutter length compensation.
- Diagnostics.
- Communication interface.
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