Since the shaft tooth accuracy is generally determined by the ring gear diameter jump, base pitch deviation, common normal length and other factors. Therefore, once these factors deviate, the hobbing accuracy will be seriously affected. The following are the reasons for errors that are more likely to occur in the current hobbing process.
1.1 Motion eccentricity
The movement eccentricity is generally manifested as a common normal length error. The reason for this error is that the generation method is generally used in the process of gear hobbing. , the transmission ratio relationship must be regarded as the main determinant of its motion accuracy. However, the transmission chain itself is not a single structure, it is composed of many transmission elements. Therefore, when the transmission chain is in motion, there must be a situation in which the error of the parts is reflected at the end of the transmission chain, that is, the inhomogeneity in the relative motion, which will affect the machining accuracy. Here, the movement eccentricity, that is, the length of the common normal line, has a certain relationship with the distribution of the gear teeth. When the gear teeth are unevenly distributed, the change in the length of the common normal line will intuitively show the maximum range of errors.
1.2 Geometric eccentricity
The geometric eccentricity is mainly the radial runout error of the ring gear. The radial runout of the ring gear mainly refers to the gear within one revolution. The maximum variation of the probe relative to the gear tooth axis will appear, that is, the eccentricity of the gear ring gear relative to the shaft centerline, which is called geometric eccentricity.
1.3 Tooth profile error
The tooth profile error mainly refers to the distance of the ideal tooth profile line normal direction containing the actual tooth profile profile line in the tooth profile working part. Generally speaking, there is always a certain deviation in the involute tooth profile, which will affect the transmission stability, and cause asymmetry, angular error, etc., and then produce the hob tooth profile error. The specific analysis of the causes of the tooth profile error shows that in the process of determining the involute tooth profile, the gear base circle is the only decisive parameter. Therefore, once the base circle error occurs, the tooth profile error will also occur. When machining gears, the involute tooth profile is guaranteed by the fixed gear ratio between the gear blanks and the hob. It can be proved that the tooth profile error of the hob determines the tooth profile error and causes asymmetry, etc. occurrence of the phenomenon.
1.4 Tooth error
The tooth orientation error occurs only within a specific range, it occurs within the full tooth width range, and at the same time on the indexing cylindrical surface, it includes the end face distance of the two design tooth orientation lines.
1.5 Roughness analysis
Roughness is generally divided into several phenomena such as fish scales, gnawing teeth, and tearing.