New tool concept for bevel and hypoid gear production on the base of stick blades - Increase of productivity and quality for high performance cutting of bevel and hypoid gears

摘要

All classic stick-blade cutting processes require a blade geometry that subordinates itself to the requirements of a positive rake angle and a sensible relief angle. This means, as a consequence, that on each blade either a cutting edge for the outer side or a cutting edge for the inner side has to be realized. The cutting edge on the clearance (inactive) side has a negative rake angle. This side is not allowed to become active and is displaced to avoid cutting contact. Hereby, especially on the tip, areas are created which have to cut chips with different chip thickness. These differences cause undesirable uneven wear behavior along the cutting edge. A second item is that the strongly restricted space on the circumference of a cutter head is used for these cutting edges which are not active in the cutting process and can not help to ensure low blade wear. A new and totally different approach led to the development of a blade design using a rake angle of zero degrees. Hereby the left and right cutting edges of a blade ar technologically equal. This blade design was called a TWIN Blade design. In the process with TWIN Blade two equal cutting edges are present on each single blade, this shape of the cutting edges cart simultaneously process both the convex and concave flanks of the workpiece. This procedure works especially well with circular arc teeth with constant gap width. As TWIN Blade cutters always have the maximum tip width, the optimum cutter rigidity can be guaranteed at all times. TWIN Blades offer further potentials regarding the tool life. The cutting load on generated workpieces can, caused by the elimination of the plunging process, be shifted from the tip of the blade to the flank. The tool life of a TWIN Blade cutter can be increased in comparison to fully coated classic stick blades by approximately 30 percent and the processing time can be reduced corresponding to the amount of increased cutting edges. But the cutting process with TWIN Blades does not only represent a remarkable benefit in performance, it also leads to a significant better pitch and form quality of the produced parts. The reason for this is easily seen: As the traditional chip form which is created during the generating the chips show a tendency to distribute themselves over the space between two blades and the two tooth flanks. Often several of these chips are wedged between the inactive cutting edge of a blade and the flank. Hereby an enormous pressure is exerted on the blade which often results in carbide chipping. The tool wear rapidly accelerates, and additionally these chips scratch the already machine finished work piece surface and leads to a poor index quality and flank form.