Gear hobbing is a very efficient and typical tooth making method. It is widely used in semi finishing of hard tooth surface and precision forming of soft tooth surface (especially large gears that cannot be ground), but the structure of machine tool, tool structure and tooth surface forming mechanism are very complex. In the process of gear hobbing, there are many error sources, many error transmission paths, complex mapping relationship and great difficulty in error control. A lot of manpower and material resources have been invested in the research and development of precision hobs and gear hobbing machines at home and abroad. Now foreign gear hobbing machines can stably process gears with grade 5 precision, and domestic CNC precision gear hobbing machines can process gears with grade 6 precision (some deviation items are Grade 6, some are lower than grade 6), The workpiece tooth surface error of gear hobbing processing has a correlation with the structural parameters of the tool, the blade error, the stiffness of the tool and workpiece system, the accuracy and dynamic characteristics of the machine tool. So far, the literature on this correlation is very rich, but most of them have only carried out qualitative analysis, and a few of them have quantitative description. Among them, there are many studies on the mapping of single error to the tooth surface, There are few studies on the influence of the heredity and coupling of multiple errors in the gear hobbing manufacturing process on the gear forming accuracy. At present, there are few studies on how to process and manufacture gears with high efficiency, high precision and low cost in China, especially on the geometric accuracy and process parameters of gear surface in the gear manufacturing process The research on the relationship between tool parameters and the dynamic and static characteristics of gear hobbing machine tools is insufficient.
1. Tool error and gear hobbing accuracy
At present, many relevant scholars at home and abroad have carried out some research on the influence of the geometric error of the tool on the accuracy of the gear workpiece. For example, Yang Laoji and others deduced and analyzed the shaping error between the tooth profile of the involute hob and the tooth profile of the Archimedes hob, and found out the relationship between the shaping error of the gear hob and various factors. Sheng Buyun and others theoretically analyzed the problem of hob profile accuracy caused by the widely used approximate forming method, and summarized the main factors affecting hob profile accuracy. Zhang Weishe and others analyzed and studied the phenomenon of concave tooth profile error near the node when gear hobbing machining high-precision involute cylindrical gear profile, and obtained the gear modification coefficient selection method to avoid the tooth profile error caused by the change of the number of teeth meshed with the tool. Domestic research on the influence of tool geometric accuracy on gear geometric accuracy and surface roughness and its control methods is insufficient. At present, a large number of studies on the transmission of tool error to gear workpiece at home and abroad are still limited to qualitative research, such as: the tooth profile error of blade will increase the tooth profile error and tooth direction error of workpiece gear; The tooth direction error of the blade will increase the tooth direction error of the workpiece gear; The helix error and cogging error of the blade will affect the tooth pitch error and helix error of the workpiece gear, but the quantitative description of these interactions is rarely reported.
2. Vibration of gear hobbing machine tool and gear hobbing machining accuracy
At present, there are few research data on the rolling vibration dynamics of NC gear hobbing machine. For example, Liu Minghui and others have carried out relevant research by using the finite element method, quasi real mode theory and vibration dynamic monitoring method respectively, aiming at the dynamic characteristics of the machine tool or local optimization design. However, there is no relevant research report on the relationship between the structural vibration of machine tool and the accuracy of gear hobbing.
3. Machining system error and gear hobbing machining accuracy
Relevant scholars at home and abroad have done some research on the systematic error of gear hobbing. For example, Zhang Lei studied the transmission of gear hobbing error flow in the multi process manufacturing process, and the relationship between system error and process output size. Yan Huiping and others studied the causes of gear hobbing system error in the hobbing process of straight tooth non-circular gear. Wu Yan et al. Studied the methods of rapid judgment and elimination of systematic errors. Xu Yaodong and others analyzed the systematic error of experimental measurement. Ye Junjun and others analyzed and modeled the system error of aspheric workpiece detection. Fu qiongfang studied the error of process system and classified and discussed the error of process system. Fan Zhonghe discussed several factors affecting the process system error in machining. Li Jian et al. Proposed a modeling method of gear hobbing machining system error based on genetic algorithm. Li Yong and others put forward the systematic error prediction model and carried out experimental analysis. Mou Ying and others discussed the influence of machine tool system error on gear hobbing accuracy. However, a large number of studies on the influence of machining system error on machining accuracy of hobbing machine tools are limited to qualitative research, and there are few reports on the quantitative research of machining error of system gear hobbing on machining accuracy.
4. Machining principle error and gear hobbing machining accuracy
There is little research on the principle of gear hobbing. Domestic scholars have done some research on the principle error of gear hobbing. For example, LV Yaofeng and others analyzed the processing principle of cold rolling involute spline and established a mathematical model. Wang Shiliang and others studied the modeling error of hob. Zhao Ning et al. Put forward the scheme of using spherical hob to transform gear hobbing machine to process face gear. These studies are related to the error of gear hobbing principle, and there are few studies on the error of gear hobbing principle.