| Involute columnar helical gear drive have quite many merits such as the good stationary property,big overlap ratio and small vibration,it is the key basic part of machinery related industry.In recent years,there are more and more demands for small batch,large modulu and complex profiled gear surface parts.It is difficult to achieve the best economic benefits by using conventional processing of gear cutting.Therefore,the flexible free-form milling technology using universal multi-axis NC machine tools and general cutters to achieve high flexibility,high precision and low cost has become a research hotspot in the field of gear processing.In this paper,the optimal matching relationship between the path of milling cutter and the accuracy characteristics of tooth profile is studied,the main research contents are as follows:(1)The basic theory of flexible free-form milling is studied.According to the transformation matrix between space coordinate systems,the coordinate transformation relationship between general end milling cutter and involute cylindrical helical gear is established,and the tooth surface coordinate equation and normal vector of involute cylindrical helical gear and the coordinate equation and normal vector of general end milling cutter are derived.According to the flexible free-form milling method,solve the location of flexible free-form milling cutter.(2)The mapping law between different tool path planning methods and residual height difference of tooth surface is studied.By numerical simulation method,the relationship between different cutter types and the number of tool path of free-form milling teeth is analyzed.When the residual height difference of tooth surface is the same,the number of tool path of universal end milling cutter is less than that of universal ball-end milling cutter.The influence of the two different feeding strategies of the equal residual height difference method and the equal step method on the tooth surface error is analyzed,and the angle of the error from the tooth surface is obtained when other conditions are the same.In terms of degree,the method of equal residual height difference control is better than the method of equal step length.The influence of basic parameters of gear on tooth surface error is analyzed,it is concluded that the residual height of tooth surface will be reduced when the number of teeth,pressure angle and helical angle of gear are increased,while the residual height of tooth surface will be increased when the modulus of gear is increased.(3)Realize NC simulation machining based on flexible free-form milling technology.Taking UG as the software carrier and herringbone gear with no tool withdrawal groove as the processing object,this paper combines the optimization matching algorithm between the feed strategy of equal residual height difference and the accuracy characteristics of tooth surface.Through simple parameter input,the setting of workpiece coordinate system and the setting of universal end milling cutter,the automatically generated G code is applied to general machining centers after postprocessing.(4)Experiments on flexible free-form milling technology are carried out.Taking the fouraxis gear milling center as the experimental prototype,the flexible free-form milling experiment was carried out to verify the accuracy of the tooth surface by three-coordinates measuring machine.The experimental results show that the total deviation of the tooth profile and the shape deviation of the tooth profile can reach ISO level 6.The lower tooth surface of the total deviation of the helix is smaller than that of the upper tooth surface,and the accuracy can reach ISO level 7.The shape deviation of the helix is smaller,and the accuracy level can reach ISO level 5.The research provides a theoretical basis for the popularization and application of flexible free-form milling technology. |
PDF Full Text Request