Spatial Forming Model Of High-speed Dry Hobbing By Interrupted Cutting With Multiple-cutting-edge And Its Application

With the advancement and in-depth development of Chinese green manufacturing strategy, the innovation and application of new manufacturing processes and equipment have become an important approach to enhance the level of green manufacturing technology. Gear is one of the most widely used parts in mechanical engineering. Hobbing is the main technique with high efficiency in gear manufacturing. But it will consume massive cutting oil and leads to problems such as environmental pollution and health hazard. High-speed dry hobbing owns advantages of high efficiency and green property in environmental protection for completely eliminating cutting oil and has been the development direction of gear hobbing. However, without the cooling and lubrication of cutting oil, issues that tool wear, machine rigidity, thermal deformation and tooth flank deviation is more sensitive to parameters such as feed rate, chip thickness and shape, cutting load. Traditional theory of gear hobbing is mainly based on two-dimensional simplified model and lack of effective mathematical tool to support the basic research on this technique. It is urgent to develop new theory and support tools. In this context, with the support of projects as National High Technology Research and Development Program(863Program) of China(Grant No. 2012AA040107) and National Natural Science Foundation of China(Grant No. 51475058), research on the spatial forming model of high-speed dry hobbing by interrupted cutting with multiple-cutting-edge and its basic application is carried out in this paper. Parameters as chip geometry, cutting force, tooth flank deviation are precisely calculated and analyzed by mathematical method. These works would provide support theory and tools for the intensive study on issues such as machining parameter optimization and error control.Firstly, the spatial forming model of cylindrical gear hobbing by interrupted cutting with multi-cutting-edge is established. In this model, the constrain relationship between designed parameters and calculated parameters involved in the gear hobbing process is initially analyzed according to the standard specification of gear design. And then the parametric model describing the geometric structure of hob for machining involute cylindrical gear is established. According to the hobbing principle, motion functions of machine components are built based on the analysis on the structure of hob machine tool and the relative movement of its components. Based on the above results, parametric equation of the edge paths surfaces engaged in the hobbing process are derived using homogeneous coordinates transformation which describes comprehensively and precisely the geometry information in cylindrical gear hobbing process.Secondly, based on the model established above, critical basic parameters engaged in the high-speed dry hobbing process is calculated and analyzed by numerical method. Include: 1) the 3D geometry of undeformed chip and its characteristic parameters; 2) the dynamic cutting force calculated using Kienzle empirical formula according the chip geometry; 3) the enveloping texture of the tooth flank which is caused by the instinctive characteristics of the hobbing process.Then, an error model for high-speed dry hobbing machine is proposed. Focusing on the radial error δx between hob and gear, the impact of machine tool structural error components on δx is analyzed. It lays the theoretical foundation for improving the rigid of machine tool. The forming error caused by δx is simulated and analyzed based on the spatial forming model. And in allusion to the problem of thermal deformation error, an experiment is carried out to study the compensation method of the radial thermal error based on the control of M-value. The forming error caused by thermal deformation is reduced effectively after compensation.Finally, a software is developed for analysis and simulation on the high-speed dry hobbing process based on the scientific computing system-Mathematica○R. And its applications are introduced. The software can support analysis on high-speed dry hobbing process of cylindrical gear.