The cutting tool is moved with sub-micron precision by a combination of electric motors and piezoelectric actuators. As with other CNC machines, the motion of the tool is controlled by a list of coordinates generated by a computer. Typically, the part to be created is first described using a CAD model, then converted to G-code using a CAM program, and the G-code is then executed by the machine control computer to move the cutting tool. The final surface is achieved with a series of cutting passes of decreasing depth.