Research On Key Techniques Of Geometrically Adaptive Machining Of Trailing Edge Of Precision Casting Closed Blisk

As a core component of an aero engine,the closed blisk has the advantages of small weight,good aerodynamics,high reliability,etc.compared with the traditional tenon structure,and is widely used in the aerospace field.When the closed blisk is manufactured using precision casting molding technology,its dimensional accuracy and surface quality of blade profile can already meet the requirements of use,However,due to the small radius and large curvature at the trailing edge of the blade,it is difficult to cast at one time.It is necessary to use a combination of casting and milling technology to adaptively process the trailing edge of the blade.In this paper,a set of adaptive milling machining schemes is proposed to compensate for the two deviations in terms of the clamping error of the closed blisk,the shape deviation of the actual blank and the design model,and to achieve the milling finishing of the blade trailing edge.Aiming at the clamping error,obtain the position information of the workpiece through the on-machine contact measurement,so as to realize the rapid clamping of the workpiece.Define the trajectory of the probe movement,the approach direction of the probe and the axial direction of the probe to realize the path planning of on-machine measurement.Aiming at the measurement error and the specific situation of the workpiece,use an algorithm based on iterative measurement and the correction of the respective degrees of freedom to achieve rapid clamping of the workpiece.The algorithms based on point-to-distance alignment,alignment along a fixed axis,alignment around a fixed axis,and rigid body translation are analyzed,discussed,and solved.In view of the deviation between the workpiece and the design model due to casting errors,correct the design model based on the measurement data to obtain a part model that conforms to the workpiece shape.Based on the fitting deviation of the measurement points on the isoparametric line,the measurement point planning of the surface to be measured is realized,with as few points as possible representing the surface to be measured.The boundary of the milling boundary is extracted and the surface model after the machining of the area to be milled is completed by cubic polynomial fitting of the measurement deviation components.In order to reduce the measurement error and perform point cloud matching on the measured data,a variant ICP algorithm is proposed which adds point-to-distance constraints to the error situation that may occurs when the classic ICP algorithm uses local data for matching.The actual curved surface is obtained by correcting the theoretical model through accurate free deformation technology.For tool path correction,three tool path transformation methods are explored and their errors are analyzed including equal parameter mapping,normal projection mapping and equal arc length mapping.Based on the characteristics of freeform deformation parameters remaining unchanged,the equal parameter is selected and the path is corrected to obtain the actual path.Finally,simulation experiments and trial cutting experiments are carried out to verify the feasibility of the adaptive milling machining scheme proposed in this paper.