Advances in tooth shaving technology

(1) Improvement of the razor blade

Currently, gear shaving cutters haven't seen the same level of advancement as other cutting tools used in the gear machining industry (for example, hobs achieved excellent results by introducing TiN, TiAlN, and TiCN coatings and allowing the use of new high-speed steel materials with cutting speeds approaching 200 m/min). During gear shaving, the amount of material removed is small, and the cutting speed is low, resulting in minimal pressure on the tool edge. Nevertheless, experts still believe it's necessary to sharpen the cutting edge of gear shaving cutters to reduce wear. The manufacturing process of gear shaving cutters hasn't changed, and coating processes haven't had a significant impact (because the side surfaces of the chip grooves are not machined after heat treatment, resulting in a rough surface that makes it difficult for TiN coatings to adhere). Therefore, experts have focused on improving the surface roughness of the chip groove sides. Newly developed CNC combing machines have significantly improved the surface roughness of the chip groove sides. Furthermore, researchers in Japan have conducted experiments on cryogenic treatment with liquefied nitrogen after heat treatment of tool materials. This method alters the properties of the gear shaving material, extending its average service life and improving the performance of the gear shaving cutter.

On the other hand, it is worth emphasizing that modern CNC gear shaving and grinding machines achieve flexibility, high precision, and speed. These three main characteristics significantly improve the accuracy of gears machined using the shaving process. This is another reason why the shaving process has not been replaced by the grinding process.

(2) Development of gear shaving machine tools and technology

Over the past 50 years, gear shaving machine tools have continuously developed, and gear shaving technology has become increasingly sophisticated. The latest CNC gear shaving machine tools can execute a wide variety of gear shaving programs (including axial shaving, diagonal shaving, tangential shaving, and radial shaving), and can switch from one shaving method to another during the shaving of the same gear. These specialized processes are all implemented under the direct supervision and control of numerical control (NC). The advantage of CNC gear shaving lies in the control of various parameters such as cutting speed, radial feed, and stroke during the shaving process. Parameters such as feed rate, cutting speed, and stroke length can be changed during shaving, making it easier to select different processing conditions. In specific gear shaving processes, in addition to the standard shaving methods mentioned above, specific processes such as "Progressive Diagonal Cycle," "Disjointed Diagonal Cycle," "Mixed Cycle," and "Twin-Linked Cycle" can also be selected.
① Progressive Diagonal Shaving

During diagonal shaving, the bulging that may occur on the tooth surface is achieved by the oscillation of the worktable around the center. This action is achieved by oscillating around the x-axis and is performed under computer control. The coordinated movement of the x, y, and w axes can create a bulge or form a cone angle on both sides of the gear. If the bulge is quite large, the amount of material to be removed is excessive, or multiple oscillating shaving operations are required, the number of oscillations on the x-axis can be set to allow for gradual removal of material at both ends.

② Mixed shaving

It is well known that radial shaving takes less time than tangential shaving, but the machined surface is rougher. The solution is to remove a large amount of material radially, followed by axial or diagonal shaving for finishing. This hybrid shaving method achieves both reduced shaving time and good surface quality.

③ Discontinuous diagonal shaving cycle, double shaving

Different tooth profile corrections can be achieved by employing two special processes: discontinuous diagonal shaving cycles and double shaving. For example, discontinuous diagonal shaving divides the machining process into three segments, and different drum shape and taper requirements are formulated according to the specific machining standards of each segment. This makes it easier to obtain special and asymmetrical convex tooth profile corrections, thereby enabling the machining of tooth profiles that correspond to the deformation that may occur after quenching, changing the gear meshing condition, and reducing gear meshing noise.