Ynneb, DNC programs have been around for quite a while in the manufacturing environment. You see, the place where hard drives are sold is a verrrry secret place, and although companies like Fanuc and Okuma and others that make controls that cost as much as a small house keep diligently looking, they don't seem to be able to discover this secret place. They've only fairly recently discovered floppy drives, but it seems they acquire them by buying a complete PC and taking the floppy out and then discarding the rest of the computer. At least, the amount they charge for the optional floppy drive would make this seem to be the case
These controls don't have lots of memory as compared to PC's either, so it has always been necessary to have some means of swapping programs in and out of any specific machine. Lots of machines are still in operation which have tape readers. Some of these have to use a card called a BTR or behind the tape reader card. This enables the machine to think its still reading data from a punched tape, when its actually reading from the memory installed on the BTR. Programs can be called from the server and downloaded into the BTR memory, and most have provisions where, if the program has to be modified at the machine to get satisfactory parts, this modified program can be uploaded back to the server. A program like camback helps facilitate all this switching and swapping, and allows access to some central storage location where all programs used in the plant are stored. One might wonder why a company would go thru all this instead of just doing a PC based retrofit and having an 80 gig hard drive at every machine. Reliability is probably one of the biggest reasons. For example, I've got a couple Okuma turning centers in my shop which are 22 years old, and the control has never been touched on either machine for any repair of any kind during that time. A person wouldn't expect reliability even approaching this level from a PC. So, you spend 1500 bucks per machine and add a BTR. Now you can plug in a laptop and load a program into the BTR memory. Or, since a laptop that's considered obsolete for most uses will still work fine for transferring files, you can put a $50 yard sale special laptop at each machine and leave it there. This approach works fine for the small shop, but you can easily see in a big plant you'd have some guy running around all day long delivering and picking up floppies and trying to remember which machine they came from or which one they go to. Not a pretty sight. So they use a DNC network and a program like camback or a similar one to replace the floppy jockey. Your guess that this type setup would be of little use to the home machinist is correct. But, to a manufacturer with tens or even hundreds of CNC machines, it's an invaluable tool for inventorying, distributing, and controlling access to hundreds of different programs.