Research On Deflection Control Strategy And Tool-path Optimization In Milling Complicated Thin-wall Parts

Complicated thin-wall parts are applied widely in the aerospace, weapons, energy,transportation and other key state development field day by day. With the high performancerequirements, the machining accuracy of such parts is required more and more highly. However,the thin-wall parts have characteristics such as thin wall, low stiffness, and poor fabricationprocedure, during high speed milling process, they generate elastic deformation easily due to themilling force and milling vibration, which led to the problem that the processing quality isdifficult to control. In the equipment manufacturing technology, as the key factor that influencesthe processing quality and accuracy, machining deformation hinders the development of nationaldefense in our country seriously. Carrying out research on deflection control strategy in millingcomplicated thin-wall parts can provide important theoretical basis and technical support forimproving process design and manufacturing level of complicated thin-wall surface parts andshortening related product development cycle, and has vital significance to the development ofChina aerospace, defense career. Therefore, taking a certain type of aircraft engine integralimpeller as the research object, aiming at the common problems of milling deflection is difficultto control, according to the milling deflection prediction model, this paper studied on the millingdeflection control strategy in milling impeller blade. The main work includes the followingaspects，(1) Deflection prediction method in finish-milling process of the complicated thin-wall partimpeller blade was studied in detail. Based on the metal cutting mechanics, the point millingprocess of integral impeller blade was analyzed and simplified reasonably. The loading methodand process of the milling force in the finite element model were analyzed. Based on finiteelement analysis software Abaqus, this paper established impeller blade milling deflectionprediction model, and then the blade machining deflection law was obtained, which providedbasis for the subsequent research on deflection control strategy.(2) Milling deflection control strategy for thin-wall parts was studied. After the factors thatresult in deflection of thin-wall parts during machining and the method reducing deflection wereanalyzed, the deflection control measures commonly used at present were summarized. Themirror compensation principle was introduced to compensate deflection at CC points, accordingto the new CC coordinates, B-spline surface reconstruction method was presented and errorcompensation surface model was obtained, namely, the ideal workpiece surface can be got after the elastic recovery of milling deflection.(3) Cross entropy method was introduced to optimize the initial tool path, which improvedthe conventional method to choose initial tool path. Then the constant scallop height tool pathplanning method was used to plan the tool path.(4) Finally, experiments of milling blade were carried out. On the one hand, the accuracy ofthe finite element prediction model was verified by comparing predicted deflections withmeasured ones, on the other hand, the validity of the deflection control strategy was provedthrough the comparison of machining errors before and after compensation.