Processing method of tyre mould in China has begun to develop in the direction ofNC, gradually abandon the traditional hand carved repair pattern process, by using five axis five linkage CNC machine carved, at the same time the design mode from atwo-dimensional design to 3D design and NC programming using CAD/CAM softwarematurity. In this paper, based on the tire mold mold 3D design and NC machining are briefly introduced.

　　1 tire tread block 3D modeling (1) tire surface model by using UG software in thesketch (SKETCH) function to establish all relevant parameters of the cavity base curve, and add the size constraint and geometric constraint. According to the radius of gyration and the needs of the pattern block rotation angle into the tire tread model using scanning characteristics of REVOLVEDBODY of the cavity base curve, as shown in figure 1.

　　(2) the curly pattern to tire top surface on the cavity curves provided by the user, the tire tread plane using TIREMAP special module will be shown in Figure 2 by theexpansion until tire top surface, and get the 3D curve in the tire top pattern (patterncurve for the space curve).

　　(3) groove modeling of tire tread pattern space curves is constructed based on three-dimensional modeling. The use of UG three-dimensional free surface modeling in the perspective of extension sheet command (EXTENSIONSHEET, ANGLED), generatingtire top part and the lateral side of the tyre tread shape, wherein the angle variablesurface using UG 3D free surface modeling in the scanning (SWEPT) generation, and through the trim body (TRIMSHEET) the excess part laid off. Through the aboveoperating groove modeling obtained as shown in.

　　The 2 key to tread pattern generating in NC machining processing program is to determine the type of processing, set up the parameter of processing, reasonable selection of tool and machine tool for the preparation of different different postprocessing program. Specific parameters need to be constantly testing, modification and get re test. UG can be processed to provide various types of optimization fordifferent processing conditions, the practical application need to be combined with the actual situation and consideration of various factors, the comprehensive use of a variety of processing methods. This paper mainly introduces two kinds of milling is closely related to the processing and the pattern block.

　　(1) the reciprocating curved surface milling reciprocating curved surface milling for processing alone have been trimmed surface.

　　By setting the tool radius and allowance for tool offset in face milling cutter, you can specify track direction, the tool path can be generated using the system, adopts the one-way cutting or reciprocating cutting. Reciprocating cutter track surface milling are parallel, the driving point generated in the processing surface. Through the chordal tolerance along the cutting direction (adjust the step size tolerances) control inputpoint number, also can specify the maximum height of two adjacent parallel tool pathcontrol of inter residue distance between parallel tool path, the maximum height and the residue is mainly affected by the cutting tool and the surface curvature effect.

　　(2) variable contour variable contour milling control method is the most complex in the NC machining, generally used for machining complex surface, in order to ensure themachining precision and efficiency. When machining cutter side or end always andsurface fitting, therefore the cutter axis is located on the surface of tangent or normal direction, in addition to the need for X, Y and Z axes, but also need to control two axes of rotation, the formation of five axis linkage