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Old June 26th, 2006, 02:55   #39
Delierious Designer of Dastardly Detonations
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Join Date: Dec 2001
Location: in the dark recesses of some metal chip filled machine shop
Yep, CNC stands for Computer Numeric Control. It's a generic term most often applied to automated machining. Before CNC there was NC which stood for Numeric Control. Machine operators punched in coordinate commands to feed machines operations one step at a time. Then they hooked up tape feed machines which read off steps in sequence (I think still called NC). Then they got rid of the tape readers and moved to computer instruction feed (CNC).

Funny thing is that modern CNC still has vestiges of the tape reel language called GCode which is still in use. GCode is a modal language which means if I instruct:

G01 X2 Y6 Z5 (go to coords 2,6,5)
X4 Y4 (now go to coords 4,4,5)

the linear move to position 1 (instructed by G01) is followed by a linear move to 4,4,5 without restating the G01 instruction or even the "Z" coordinate (which hasn't changed).

The ultimate in spaghetti code goodness as many modern programming languages do not assume implied commands as GCode does. The reason GCode allows implied commands and positions is that it required less manual keying in NC systems and less hole punching in the old tape and reel setups which ran a physical tape with holes in it! Funny bit of codecrap to carry over into the computerized machining era.

Now much of the GCode sent to CNC machines is generated by CAD extensions which crank out GCode based on solid or 2d model. Still many of the modal features persist.
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