During machining, the machined surface of the workpiece is obtained by the relative motion of the cutting tool and the workpiece. According to the surface forming method, cutting can be divided into three categories: tool path method, forming tool method and generating method.
(1) The tool tip trajectory method relies on the motion trajectory of the tool tip relative to the workpiece surface to obtain the required surface geometry of the workpiece, such as turning the excircle, planing the plane, grinding the excircle, turning the formed surface with a profile, etc. the motion trajectory of the tool tip depends on the relative motion of the cutting tool provided by the machine tool and the workpiece;
(2) The forming tool method, abbreviated as forming method, is to use the forming tool that matches the final surface contour of the workpiece, or the forming grinding wheel to process the forming surface, such as forming turning, forming milling and forming grinding. Because the manufacturing of the forming tool is relatively difficult, it is generally only used to process the short forming surface;
(3) The generating method, also known as the hobbing method, refers to the relative generating motion of the cutting tool and the workpiece during machining, and the instantaneous center lines of the tool and the workpiece are pure rolling with each other, and the determined speed ratio relationship between them is maintained. The obtained machining surface is the envelope surface of the blade in this motion. Gear hobbing, gear shaping, gear shaving, gear honing and gear grinding in gear machining are all processed by the generating method.
(4) Some other cutting processes have the characteristics of both tool path method and forming tool method, such as thread turning.
