Instantaneous Cutting-amount Planning For Deformation Homogenization Of Thin-walled Surface Parts

Thin-walled curved surface structural parts have been widely used in aerospace industry,national defense industry,war industry and vehicles,features as small quality and higher strength.The complex curved surface thin-walled parts often work in extreme conditions,such as high temperature,high pressure,large load,so the accuracy recommend is higher and stricter.And 5-axis nc machine tool is widely used in machining thin-walled curved surface parts.Thin-walled structure makes thin-walled curved surface parts have the machining characteristic of low stiffness and the position-relationship stiffness.For the instantaneous cutting-amount is changing during 5-axis nc machine process,result in inhomogeneous deformation for the machining position of the thin walled part.As a result,the large contour error of the parts is caused,which makes the machining precision difficult to meet the requirements and affects the performance.At the present,The machining deformation compensation of thin walled surface parts is an effective way to improve the machining deformation of thin wall surface parts,however there are still some shortcomings,on one hand the conventional machining deformation error compensation relies on the accurate cutting force modeling,which is difficult for 5-axis nc machining,on the other hand the compensation effect of deformation is not ideal,so it is necessary to adopt the method of iterative calculation compensation to improve the machining precision which seriously affect the machining efficiency.Therefore,it is of great theoretical and engineering value to study the efficient method of restraining the machining deformation of thin-walled curved parts.For the deformation is effected by the cutting force and the cutting force is effected by the instantaneous cutting-amount in essence.The constantly changing cutting amount in the process causes the fluctuation of cutting force,which produces the different machining deformation along the machining position,bringing a very high requirement for the efficient compensation of machining deformation of thin wall surface.Based on the instantaneous cutting-amount model and the change rule of stiffness of thin-walled surface under the influence of geometric features,a rigidity-guided instantaneous cutting-amount planning approach in machining of the thin-walled curved surface parts is proposed in this study,so as to homogenize the machining deformation thus improving the surface quality.Based on the instantaneous cutting-amount planning to redesign of feed speed,combined with the semi-finishing parts based on deformation uniformity,one-time efficient mean error compensation,control the deformation to effectively for thin-walled curved surface parts milling process,realize the high quality and efficient processing.The main research contents of this paper are as follows:Firstly,a typical complex thin-walled impeller blade is taken as an example,based on the principle of b-spline surface,a blade geometry model is established.Then generated a non-interference machining-path for the five-coordinate end milling.Set up a coordinate system including tool coordinate system,local coordinate system and the workpiece coordinate system,studied the relationships between different coordinate system transformations.According to the geometry of micro contact relationship,considering the workpiece geometry features,cutting tool geometry and cutting conditions,established an instantaneous cutting model for end milling blade parts by flat-tool,laying the groundwork for the behind planning of instantaneous cutting amount.Then established the finite element model to simulate the actual processing,the model considered the changes of the effective cutting width during flat end milling process,the elastic deformation calculations for thin blade at each cutter contact is calculated for obtaining the stiffness variation based on geometric features of the thin blade.Based on this,a method for planning the instantaneous cutting amount of the five-coordinate end milling thin-wall curved surface is proposed.Experiments result show that the reasonable processing parameters of the plan based on the instantaneous cutting amount can effectively homogenize deformation of the thin-walled curved parts.At last,take blade section machining for example,planning tool path according to the previous section of the instantaneous cutting amount planning method,using an A/C double-turn table 5-axis nc milling machine to take experiment.The result show that the proposed method in the paper can effectively homogenize the deformation for thin-walled curved surface parts in milling process.Then the error mean compensation method was adopted to compensate the thin walled part.Compared with the conventional error compensation method,the machining accuracy can be improved by 30%.The above content provided certain reference for subsequent further studies of machining deformation for thin-walled parts with curved surface,at the same time,also provided positive guiding significance for actual production processing.