Trajectory Modification For Laser Processing Of Surface Pattern On Thin-walled Parts Considering Clamping Deformation

High-precision metallic surface pattern is the core functional structure of key parts such as high-performance antenna.Its processing is gradually based on laser etching with the parts' development of lightweight design and structure-function integration.However,due to the deformation of thin-walled surface under clamping force,the ideal machining path causes problems such as beam defocus and deviation of the pattern's shape and position,which restricts the machining accuracy.In view of this,this paper carried out the research on trajectory modification for laser processing of surface pattern on thin-walled parts considering Clamping deformation.The contents are as follows:Firstly,the requirement of workpiece-fixture friction for thin-walled rotary parts is clarified.The clamping position is simplified as the flat circular plate clamped peripherally with force-induced deformation,and the calculation shows that the deflection exceeds the traditional focal depth of laser.Based on the basic theory of heat transfer and laser,the prediction model of ablation cross-section of metal by moving pulse laser under focusing and defocusing conditions is established.The results of microgrooves on aluminum surface show that the profile and ablation size with defocusing amount are in good agreement with the predicted results,and the prediction errors of maximum ablation depth and width are 5.69%and 8.05% respectively.The allowable focal depth of laser is 0.52 mm according to the ablation size tolerance.Considering the characteristics of laser processing and the accuracy requirements of surface pattern,the method of planning step size is proposed.Secondly,the effect of radial clamping force on thin-walled cylinder is simulated by ANSYS.The size and distribution of axial,radial and tangential deformation are analyzed.The deformation direction vector of any point on the ideal surface is solved by interpolating the coordinates of that of given nodes,and combining with the surface model the surface mapping relationship is established.The quadrilateral mesh surface is constructed by the point cloud of the clamped surface,and the solution of mapping trajectory points is abstracted as the intersection of ray and quadrilateral mesh,then the algorithm flow is established.The linear pattern is processed on the flat plate,and the approximate circular clamping deformation is equivalent to the lifting amount of the laser head.The results show that there is a negative correlation between the groove depth and the lift of the laser head,which verifies the necessity of further planning of trajectory points number.Thirdly,the curves of spot path and ideal pattern are defined and the corresponding curvature radius calculation methods are established.According to the change of trajectory step size before and after mapping,the region of trajectory point number optimization is planned.According to the deviation between the actual path and the ideal path of laser focus,the error evaluation functions of ablation depth and pattern profile are established,and the method of encryption and simplification of mapping trajectory points under the constraint of error threshold is discussed.Based on the multi coordinate system model of 5-axis NC laser processing machine tool,the transformation formula of coordinate from the planning trajectory point to the laser focus is established.Furthermore,the post-processing module of trajectory points for NC laser processing is developed.Finally,the proposed method is used to plan the trajectory points for the straight line of rectangular pattern.The trajectory shape basically conforms to the deformation law of the workpiece,which verifies the universality of the method for special patterns.The pattern of star cycloid array is further processed.The results show that the error of ablation depth and width is suppressed by 72.72% and 86.41% respectively,and the deviation of etching depth and width is both less than 5%.The circumferential relative position accuracy of pattern array is improved by about 20?m.The circumferential dimension accuracy of pattern is improved by 120?m.And the geometric characteristic of star cycloid are better preserved.Based on MATLAB,the software of automatic generation of laser processing path for surface pattern on thin-walled curved surface is developed.The research results provide theoretical basis and technical support for the surface pattern processing on thin-walled surface,which can be used for reference in high-precision machining of metal pattern on typical rotary parts.It also provides a reference for manufacturing of precision parts in aerospace,information and other fields.