1. Hard surface gear

The hard tooth surface processing technology is mainly applied to the gear finishing whose tooth surface hardness is higher than 45 HRC after heat treatment. The purpose is to improve the efficiency and quality of the gear finishing and reduce the processing cost. The main processing methods are for the hard tooth surface shaving fine rolling (scraping) tooth grinding and honing, etc. Compared with the traditional processing technology, the hard tooth surface processing method can improve the tool materials and coatings of machine tools tool technology and other higher requirements.

Hard gear surface machining technology is mainly applied to gear finishing whose tooth surface hardness is higher than 45 HRC after heat treatment, aiming to improve the efficiency and quality of gear finishing and reduce the processing cost. The main processing methods are for hard tooth surface shaving, fine rolling (scraping), grinding and honing, etc. Compared with traditional processing technology, The machining method of hard tooth surface puts forward higher requirements for machine tool, tool material and coating, tool technology and so on.

Gear honing and grinding can use electroplating or sintering grinding tools of CBN or diamond superhard abrasive. The forming grinding tools of CBN grinding wheel are shown in Figure 3, and the rough-finishing cutting tools are designed into combined cutting tools during tool design. The number of working procedures can be reduced by using coated HSS or cemented carbide cutting tools for tooth shaving and fine rolling on the hard tooth surface.

Compared with the traditional technology, the superhard tool material grinding wheel can significantly reduce the surface roughness, improve the surface quality, and improve the accuracy of 1~2 degrees. The processing efficiency is more than 25 times of the conventional tooth surface grinding. In order to adapt to the requirements of the hard tooth surface gear processing, the machining machine pays more attention to the CNC technology, high-speed machining and multi-function.

2. Strong precision honing

Due to the limitation of the gear hobbing and shaving heat treatment grinding process commonly used in gear processing in high precision automotive transmission gear processing, it is difficult to meet the technical requirements of gear to grind the hard tooth surface after heat treatment, and then adopt the honing method to improve the quality and the processing cost is high However, it is an efficient method for high precision gear machining to use strong gear honing directly on the hard tooth surface.

When the manufacturing cost is close to the traditional process, higher machining precision and surface quality and machining efficiency can be obtained, showing good economic benefits. The tooth shape and direction correction of strong gear honing can be greater than 0.05 mm, can correct the heat treatment deformation and micro-defects, surface roughness can reach Ra0.2μm below, after heat treatment using strong gear honing process, can reduce the surface wear caused by grinding teeth, avoid the resonance and noise generated in the transmission gear meshing process.

The tooth surface has a large residual compressive stress, which significantly increases the strength, wear resistance and pitting corrosion resistance of gear. In the process of strong gear honing, the tool slides relative to the tooth surface and removes the workpiece material at the same time. The cutting speed is low, which avoids the tooth surface burn caused by high-speed grinding in the process of gear grinding.

Compared with gear grinding, gear honing can process the gear with shoulder. Although the precision is slightly lower than that of gear grinding, the cost and comprehensive efficiency of strong gear honing are obviously better than that of gear grinding process. Gear honing costs about 50% of the shaving cost and 20% of the grinding cost.

Therefore, the application of strong gear honing process in high-precision gear machining of automobile transmission has great advantages, and improves the reliability and stability of transmission operation, extends the overhaul cycle, and reduces the problem of automobile noise. The process route of high-precision gear machining of automobile transmission can be simplified into rolling, shaving, honing, and even the strong gear honing can be carried out directly after hobbing.

---EDITOR: Doris Hu

---POST: Doris Hu