0
$\begingroup$

I am trying to really understand the difference between NC and CNC machines (not just to see the "old dark-green display" to know that it is an NC machine).

On the web people are saying that Numerical Control (NC) uses instructions of letters, numbers and symbols to control the machine, and Computer Numerical Control (CNC) uses a program to control the machine. But what is a program then a G-code, and what is G-code than a set of letters, numbers and symbols?

I do not have experience with NC machines, so I came to the question if they also use G-code, and what would be a really clear example of the difference between the NC and CNC concept?

$\endgroup$
5
  • $\begingroup$ Maybe you just don't know what to search for but I found the answer really quickly. NC Machines use punch cards. Weird huh? And they did use G-code which is why it looks so strange compared to the normal computer programming languages you are used to. They probably jumped to CNC as fast as they could since it is such a natural step. NC machines are like gyrocopters and CNC is like helicopters: a peculiar stopgap in technology that is missing extremely natural and desirable functionality. And they did use G-code. $\endgroup$
    – DKNguyen
    Oct 14 at 16:40
  • $\begingroup$ Thank you for your efforts but I was not looking for somebody who can google me an answer, rather for somebody who can speak about real world experience. If you read again your comment, you say that NC's used also G-code so people jumped to CNC. But the question still remains - what makes a CNC different from NC if they both use G-code to speak to the machine? It can not just be the colorful display on a CNC machine to say 'well, we will call this NC a CNC because it looks a bit more modern.' $\endgroup$
    – elano7
    Oct 14 at 17:37
  • $\begingroup$ Like I said, NC is punch cards as opposed to "soft"ware, as well as relays and valves. Not solid state. thomasnet.com/articles/custom-manufacturing-fabricating/… You're probably defining a computer as something broader than what the people who made the definitions are using. $\endgroup$
    – DKNguyen
    Oct 14 at 18:47
  • $\begingroup$ I can not agree with you or the author of the blog post that NC machines use only punch cards. NC machines are today still widely used and who would be crazy to use a machine with punchcards? Just type on a website like machineseeker the term NC mill and you will find tons of machines that in their names have the indication that they are NC machines (even in the specification they are defined as Numerical Controlled), and I am talking about machines manufactured on demand = new machines. As I told you, google is not the solution for this question as the answers are mostly some copywriting. $\endgroup$
    – elano7
    Oct 15 at 20:23
  • $\begingroup$ The reason you don't believe seems to be that it is just such a foreign concept to someone accustomed to modern computers. I just asked my coworker who has been a toolmaker for 50 years what the difference is and he just repeated what I told you with a few additions: "An NC machine takes punch cards or tapes. It comes with a special typewriter thing that you write your program on and the it produces the punch cards or tapes which you then you stick that into the machine and it runs straight through the program." $\endgroup$
    – DKNguyen
    Oct 15 at 21:04
0
$\begingroup$

An NC machine, instead of having wheels like a manual machine, accepts instructions and numbers. But unlike a CNC machine, a computer is not feeding it those instructions and numbers.

An NC machine comes with a special typewriter thing that you use to write your program and it produces the punch cards or magnetic tapes that the NC machine accepts. You then take the tape or card and put it into the machine and it directly runs through the instruction set. A key distinction from a CNC machine seems to be the fact the "program" in an NC machine is run straight from beginning to end, and you traditionally could not just "drop in" and make an edit in the middle, unlike computer software. If you want to debug, fix it, or make a change, you have to make a whole new tape or card set.

The fact we have desktop computers now that could produce magnetic tape (or punch cards) to stick into the NC machine eases programming (you can make edits in the middle instead of making a brand new card or tape each time), but does not change the fact that the NC mill, lathe, etc. still only accepts the magnetic tape or punch cards as the source of its instructions. This is different from a CNC machine that has a computer inside it that executes a program stored on storage media (which could be magnetic tape, but nowadays a magnetic disk, hard-drive, or flash-drive).

Some NC machines did use G-code but there were other alternatives as well.

$\endgroup$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.