Research On Dynamic Modeling Of Cutting Vibration Of Dry Gear Hobbing And Machining Precision

Dry gear hobbing is one kind of gear machining methods based on generating method,and it is the most popular gear machining method because of its high productivity,environment-friendly,wide versatility and high machining accuracy.In the process of gear machining,the dynamic and static characteristics of machine tool have a great influence on machining quality and gear precision.The time-varying cutting force of gear hobbing is a key factor which forces the machine tool to vibrate.The cutting force is a dynamic force relate to the variation in cutting thickness which cause self-excited vibration of cutting system and result in machining chatter.Machining chatter will reduce cutting parameters and surface quality of gears,and generate much noise and even damage the cutting tool early.For this reason,an accurate calculation method of time-varying cutting force and dynamic model of the system of the gear and cutting tool provides a basis for studying the mechanism of cutting chatter and monitoring the conditions of machining system.The paper aims at the gear hobbing system and presents a calculation method of time-varying cutting force with multi-tooth cutter.A four degrees-of-freedom dynamic model of gear hobbing vibration is established,and t he effects of different cutting parameters on the dynamic characteristics are obtained.Also,a vibration experiment of gear hobbing is carried out,and the experimental data and the results of theoretical calculation are compared and analyzed.The main research work includes:(1)According to the mechanism of gear hobbing and the theory of metal cutting,the unsteady and approximately steady stages of the process of gear hobbing are defined.A calculation method of the time-varying cutting force is proposed,by considering single tooth cutter and 2-tooth cutter.The effects of different cutting parameters on the time-varying cutting force are analyzed,and the cutting forces of different rotation rate,feed per tooth and depth of cut are obtained.(2)A four degrees-of-freedom dynamic model of gear hobbing vibration is established.The dynamic response of gear hobbing and the effect on machining accuracy by vibration are analyzed,and the effect on dynamic responses by different rotation rate,feed per tooth and depth of cut are obtained.(3)For the machine tool of dry gear hobbing,the acceleration sensor and LMS system is applied to test the influence on vibration acceleration by different rotation rate,feed per tooth and depth of cut.The theoretical and experimental results are analyzed in time domain and frequency domain,and studying the effect on profile deviations by cutting parameters in gear measuring center.