Research On Some Key Technologies Of Hobbing Force Prediction Of Cylindrical Gear

Every high performance gear transmission module is composed of cylindrical gear.Cylindrical gear can be manufactured with a series of methods,of which gear hobbing is the most widely applied.Cutting force is one of the basic physical phenomena of gear hobbing process,and has the direct effect on cutting vibration,cutting heat,hob wear and machining deformation.The thorough knowledge of the developed cutting forces are of great importance in order to produce cylindrical gear gears as they influence the cost of the manufacturing process and the quality of the produced gear and high performance machine tools.This thesis aims to solving geometric simulations of gear hobbing process and cutting forces prediction.The relationships of the contents of this paper are mathematical model of the hobing cylindrical gear—hobbing force modeling—identification of cutting force coefficients—hobbing force measurement—numerical analysis of strength of hob tooth.Based on three-dimensional solid modeling method,the effective solutions of application integration from geometrical simulation of the gear hobbing process to cutting force prediction was put forward.The main contents are presented as follows:(1)The mathematical model is the base of imulation of the hobbing cutting process.According to multibody system theories homogeneous coordinate transformation matrix and generating motion relationship,the position vector and velocity vector of arbitrary point on cutting edge of hob were achieved.The movement relations between hob and workpiece for different types of gears generations were analyzed.Numbering rule of hob tooth was described and the coordinate system of hob tooth was established.Then the mathematical model of hob tooth profile was presented.The active tooth numbers and its application scope were determined by imaginary rack and research results of Terashima K.The total hob travel distance was divided and chip shape was described in different hob travel distance.(2)The gear hobbing force was generally taken to be a function of geometric parameters such as chip thickness.Firstly,based on the principles of solid modeling set forth in the hobbing process,relevant calculated position was defined.The method of application of solid modeling for hobbing simulation was analysed,geometrical simulation of material remove process for gear hobbing was proposed,by which undeformed chip solid geometry and gear gap were developed.Secondly,by Coordinate transformation in spatial modeling system,the chip layer was extracted from the udeformed chip,further to determine the geometric parameters of chip thickness,which is applied in hobbing force model.Finally,the produced gear tooth profile error was analyzed and gear tooth surface was reconstructed in which the accuracy and efficiency of the above method can be proved by gear tooth profile error.(3)Reseach on modeling of cutting force in hobbing and establishment of cutting force model for gear hobbing.By studying the micro-mechanics model on cutting element analysis according to the mechanical model of Kienzle,Victor's,the cutting force model of hobbing which is modified by taking account the interference of chip flow;with tool discretization and cutting force vector superposition,cutting force model for gear hobbing is established.Simulation algorithm of hobbing force was carried out.By determining whether chip thickness was achieved by tooth,the cutting forces for different tooth could be overlapped and its process judgment criteria was also realized.(4)Cutting force coefficients is a key factor to affects the accuracy of the prediction for hobbing force.Based on research the determination method of coefficients about Kienzle-Victorl cutting force model,flycuter rotating cutting force experiment similar to turning was carried on,linear relation between cutting force Fc and cutting width b of Kienzle-Victorl cutting force model were validated and cutting force coefficients were determined.Force model of linear flycuter cutting involving chip flow interference was established.According to simulation results of linear flycuter cutting force and those obtained from experiments,the coefficients of Kienzle-Victorl cutting force model involving chip flow interference were obtained by regression analysis.The results showed that respect to a single right angle cutting edge the cutting force coefficient parameters change significantly under the interference of chip flow.(5)Experimental verification accuracy and reasonableness of hobbing mechanical model.Experiments were carried out on the DMU50 five axis machining centre,by the way the hobbing force measurement was designed including motion relationship generation and NC program edition,above all the application of electronic gear box function of SINUMERIK 840D.The total cutting forces as well as the cutting forces in every cutting edge involved in the hobbing process were calculated.By comparison between the measured hobbing forces and theoretical calculated ones,the validity and accuracy of the proposed methods were confirmed.The overall structure of simulation software HOBBING3D and its module function were described detailed.(6)Base on hobbing force model has been established,the analysis of hob strength was carried out which provide a theoretical basis for optimization of hobbing process.APDL Language in ANSYS was used for analysis of strength of hob tooth.The load applied on finite element model of hob tooth was obtained from HOBBING simulation software.Cutting force distribution area was determined by corroding to the hob cutter instantaneous unreformed chip,which improved accuracy and efficiency of analysis of strength of hob tooth.The results showed simulation results can be described knife stress state and distribution of hob tooth including to explain the early fatigue failure causes.Further more it provide a theoretical basis for optimization of hobbing process parameters.Overall,in this paper the key technologies of cylindrical gear hobbing force prediction were studied.The related research result contrary to hobbing mechanism has important theoretical and practical value.