Tool Orientation Planning In Five-axis Milling Of Propeller Surface Based On Machining Error Estimation

The propeller is the core component of vessel dynamic propulsion system.The level of manufacturing of propeller affects the scientific research pace of vessel dynamic propulsion equipment.With the further improvement of vessel dynamic propulsion equipment permachiningance requirements,the geometric design of propeller becomes more complex.The complex features of propeller,which includes a large number and long overhanging of blades,distorted blades and big overlay district between adjacent blades,not only make the machining feasible space more narrow but also force the engineer to choice long overhanging and large length-diameter ratio tools.These cases make the tool stiffness more poor and tool demachiningation more easier to appear in machining process,leading in more difficult control of machining precision.At present,most of scholars at home and abroad study tool orientation planning from the perspective of kinematics and geometry.With the research of milling mechanism continue to make progress,it is especially important to consider cutting force,tool deflection,and other physical factors in tool orientation planning.Therefore,for the machining precision control of propeller scale model blade surface,this thesis studies the parametric cutting force model,tool deflection model and machining error model in five-axis machining.Base on these,this thesis also studies tool orientation planning method and applies it in machining of propeller scale model.A parametric cutting force model based on the mechanical model in five-axis milling is built.Undemachininged chip thickness model is built and parameterized expression machiningula of undemachininged chip thickness is deduced.Three cutter/workpiece engagement area boundary curve equations is deduced and parameterized model of cutter/workpiece engagement area is built,and then the judgment algorithm of cutter/workpiece engagement area is given.Base on these,parametric cutting force model is built and the three-direction cutting forces are expressed as a function of tool lead angle and tool tilt angle.In the end,the validity of the cutting force model is verified by eight experiment groups under different tool orientation.A tool deflection model and a machining error model are built.The developing of cutter static flexibility model is divided into two parts.One is the stiffness model of motion-spindle-handle system,which is obtained from experimental calibration and theoretical calculation,another is the stiffness model of cutter system,which is obtained from accurate theoretical calculation.Calculating the instantaneous cutting force of cutting the cutter contact point and building the model of the static cutter deflection.Building the machining error model by projecting the deflection displacement of the end of the tool to the normal vector of the workpiece surface.In the end,the validity of the machining error model is verified by 36 experiment groups under different tool orientation.A tool orientation planning model based on machining error estimation of workpiece surface is proposed.For the milling of the main blade area of propeller scale model,the tool orientation planning optimization objective based on the minimum machining error is established in the first,and then the simplified workpiece surface and the space constraints of tool orientation are established.The machining efficiency constraints are given based on the minimum material removing rate and the maximum scallop height.Building the tool orientation planning model and developing the planning process of tool orientation planning,and then the program calculating progress of solving the model and tool path generation.In the end,the validity of the tool orientation planning model is verified by six comparison experiment groups.The tool orientation planning method is applied in machining of propeller scale model.Appling the tool orientation planning method in the machining of the whole blade area and the edge area of blade,and the measurement results verify that the method can satisfy the requirements of machining precision and achieve good permachiningance.