CNC routers are controlled by a computer. Coordinates are uploaded into the machine controller from a separate program. CNC routers are often used with two software applications—one to make designs (CAD) and another to translate those designs into a G-code program of instructions for the machine (CAM) in vertical, horizontal, and perpendicular coordinates. As with CNC milling machines, CNC routers can be controlled directly by manual programming, but CAD/CAM allows wider possibilities for contouring, speeding up the programming process, and in some cases creating programs whose manual programming would be impractical. On some controllers, the G-code can be loaded as a vector file on the router control panel. A vector file can be created from a picture file by using drawing (CAD) software.
The human operator selects the machine tool (such as a 0.25-inch v-bit or a 0.75-inch core box bit), speed, cut depth, and tool path. Most machines give the options of tracing the vectors, cutting outside the vectors, or cutting inside the vectors for the cut path. The operator determines the center point of the part, clamps the part onto the table, moves the bit directly above the marked center and down to the face of the part, and marks this as the starting point. The operator moves the bit up a few inches and selects the run G-code function. The machine begins to cut the design.