Curious...What does CNC stand for?

[Pat Dowdel]

Good Morning All,

OK, time for the stupid question...
I was curious what CNC stands for; I assuming something like "cutting ..."
Also, can someone tell me kind of laser is a a CNC Laser (CO2/YAG etc)

And be gentle, remember what your 3rd grade teacher always said...there's no such thing as a stupid question ;)

Patty

[Michael Stafford]

Computer Numerical Control...let the bits and bytes do the thinking for you....;)

[Mitchell Andrus]

CNC... Computer Numeric Control. Goes with CAD and CAM.

Computer Aided Design and Computer Aided Manufacturing.

There are minor variations. This is all short hand for 'automation' but it means the machines have taken over and now, even an idiot can cut steel to 0.001" tolerance if the boss spent enough money on tooling.

Mitch

[Lee DeRaud]

Computer Numerical Control.

Term was invented to describe the codes (generated by CAD/CAM systems) used to control automated milling machines etc. The lasers and stuff we use today use a different set of control codes, but the name has stuck.

[Hale Reider]

The term CNC was an extension of NC, which stood for numerical control. Back in the 50's, someone was able to take a Bridgeport style mill and program it to move and do 2 axis contouring using punched cards created on a room sized IBM.

That evolved into the early NC controls (example GE 100) which used punched paper tape that was created on a Flexwriter or Teletype machine. The machine ran the tape each time it made a part. To reprogram it, you made a new tape. To run the same part over and over, you used a looped tape and usually made a milar tape. The tape reader had little lights in it that read the punch marks. Any stray chaff caused a wreck. In the late 70's, NC was replaced by CNC, when they figured out how to store the date.

I sell metal cutting machine tools for a regular living. We still refer to the amount of memory on many of them in feet, as in feet of punched tape. These machines still run a code called ASCII.

There is also something called DNC, Direct Computer Control, where one computer might run several machines that only are dumb controllers (no internal processor). Some multi-axis machines may have a number of processors. I sell stuff with 7 to 9 axis. A large manufacturing cell may have a dozen machine all automated and working together with a cell controller.

A stamping die to make a fender might have a million lines of code, all created by a CAD/CAM system. To smooth it out, they might use something call NURBS, another term you should look up.

Hale Reider
Tobecherished.com

[Vaughn McMillan]

Cool education Hale. Thanks for the background.

- Vaughn

[Mark Singer]

Canned Nuts of California:confused:

[Mark Card]

The term CNC was an extension of NC, which stood for numerical control. Back in the 50's, someone was able to take a Bridgeport style mill and program it to move and do 2 axis contouring using punched cards created on a room sized IBM.

I read about researchers at MIT in the late '40's having several machinists hand operate each axis on a large boring mill simulating Numeric Control. They scapped the part but it was still considerd a success in proof in concept.

That evolved into the early NC controls (example GE 100) which used punched paper tape that was created on a Flexwriter or Teletype machine. The machine ran the tape each time it made a part. To reprogram it, you made a new tape. To run the same part over and over, you used a looped tape and usually made a milar tape. The tape reader had little lights in it that read the punch marks. Any stray chaff caused a wreck. In the late 70's, NC was replaced by CNC, when they figured out how to store the date.

Adding the computer did allot more than remove the line by line reading of the tape though. Cutter compensation where the diameter/length of the cutter can be programmed as nominal and can be adjusted at the machine was huge. Early NC machines could only simulate cutting a circle. They would move in a point to point fashion so a circle would consist of say 200 mini flats, to increase the "roundness" of a circle you would increase the number of data points it moved the two axis's to increase the resolution. This gets realy ugly without the computer when you add more axis's at the same time for helical items like a spiral.

I sell metal cutting machine tools for a regular living. We still refer to the amount of memory on many of them in feet, as in feet of punched tape. These machines still run a code called ASCII.
To further extrapolate ASCII is a standard code to identify the main charecters on an english language keyboard. Its based on giving a 8 bit number to each charecter both in lower and upper case. The actual commands submitted to the machine tool are in ASCII but the native code is written in M&G commands. G00 would be rapid movement G01 would be a linear move and so on. Generaly a CAD (Computer Aided Drawing) would be submitted CAM (Computer Aided Manufacture) program to output in ASCII the M&G codes to move the axises. This can all be done by hand as well with some shop trig untill you get into 4+ axis helical movements.

There is also something called DNC, Direct Computer Control, where one computer might run several machines that only are dumb controllers (no internal processor). Some multi-axis machines may have a number of processors. I sell stuff with 7 to 9 axis. A large manufacturing cell may have a dozen machine all automated and working together with a cell controller.

A stamping die to make a fender might have a million lines of code, all created by a CAD/CAM system. To smooth it out, they might use something call NURBS, another term you should look up.

Hale Reider
Tobecherished.com
The big difference in a machine tools compared to my Explorer laser is the graphic program/print driver combination eliminates the need to generate the M&G code. The print driver coupled with our comodity priced generic computers makes the laser control a snap in comparison.

If you where to buy a hobbiest level machine tool like a Shearline mill you don't simply "print" a graphic to the mill and off it goes. You need to generate a file of commands in M&G code that give in exacting detail each move of the machines axises.

Cheers
Mark

[Dave Jones]

I'd like to add that ASCII (American Standard Code for Information Interchange) was actually a 7 bit code (originally called ASCII-7). From what I remember of punched tapes, the most common had 9 holes. Seven for the ASCII, an 8th bit for parity (exclusive-or of the 7 bits for error checking), and a ninth bit which was an index (one hole per character, almost like a sprocket hole).