CNC is the acronym of Computer Numeric Control and it is often associated with plasma cutting as in CNC plasma cutting. A plasma cutting unit that is controlled by CNC is controlled by a computer. There are two basic classes of controls, industrial PC-based control systems and hobbyist/artisan PC-based control systems. The industrial CNC systems, such as the ones produced by Hypertherm or Burny, are robust enough to stand up the harsh production environments. They have a touch screen that can be housed inside of a heat shield for additional protection. The industrial CNCs are very costly, but they come highly recommended for any application because they are not vulnerable to typical PC problems meaning they have very little down time. Due to the high cost you will not often find industrial scale CNCs in a hobbyist’s garage. The artisan and the hobbyist plasma cutter use standard PC-based controls with I/O cards for controlling the plasma systems and the drives. Since these are regular PCs they are prone to an array of computer problems, but none that cannot be fixed.
If you want to use a CNC for your plasma cutting there are some things you will need. You will need a table for the cutting to take place on. On each side of the table you must have a rail that the drives can use to move the plasma systems; we will call this the x-axis. A bridge or gantry must span the table and each end must rest on the rails. The plasma system must be attached to a rail on the bridge which will allow it to move back and forth; the y-axis. Industrial strength set ups us fabricated steel for the construction of the table, rails and bridge. On the other hand, extruded aluminum is used for the hobbyist and artisan CNC plasma cutter set ups. The difference is that the steel is more robust and will withstand constant use whereas the aluminum can only withstand occasional use. If building one of these machines sounds a little scary to you, there are lots of kits that you can buy or you have the option of buying ready built CNC plasma cutters.
If you cruise the web you will be able to find many videos showing CNC plasma cutters in action. It is not the easiest topic in the world to explain and I suggest you check out some videos if you have not seen a CNC plasma cutter before.