A Study On Influencing Factors Of Quality For CNC Incremental Forming

At present,the study on influencing factors of quality for CNC incremental forming is mainly from the aspects of the feed parameters,the layer spacing and forming tool size,etc,and evaluation indicator is also considered unilaterally from the thickness or the surface roughness.But,the forming quality indexes such as contour accuracy and surface quality have not been taken into account comprehensively from the aspects of forming method,forming support die completeness and forming path.In this paper,the study on influencing factors of quality was from the aspects of forming method,support die completeness and forming path,and the design of forming scheme and path planning were given.Through the finite element analysis and the actual forming experiment,the specific influence of each factor on the forming quality of sheet metal was discussed and the optimal choice of the parameters was given.It provides a strong basis for the parameter setting and optimization of incremental forming technology,and provides a technical basis for the research and application of the technology.Firstly,for the forming of special shaped sheet parts,the forming methods were innovated.For the double convex sheet metal part,the method of CNC incremental reverse forming based on double extruding was proposed and the forming process scheme was given.For some sheet parts were not be formed only by single positive forming or negative forming,a compound forming method based on combination of positive forming and negative forming was proposed,and three kinds of forming sequences such as negative-positive forming,positive-negative forming and positive and negative parallel forming were given.Secondly,in order to solve the problems of support adoption or what type of support adopted in CNC incremental forming,the influence of support integrity on the forming quality was discussed.Taking the typical sheet metal parts as research objects,the forming quality was analyzed by three types of supports,full support die,partial support die and no bottom support die.Thirdly,by contrastively analyzing the surface residual height of incremental forming part and CNC milling part,the applicability of residual height calculation method of CNC milling in CNC incremental forming and the practicability of the constant residual height path in CNC incremental forming part were studied.Fourthly,in order to improve the contour dimensional accuracy and surface quality in CNC incremental forming,a forming process that the size errors caused by rebound deformation were corrected and the residual traces were eliminated by the secondary extrusion was proposed,and path planning and generating method of secondary extrusion forming was given,which could make the extrusion tool accurately crush the residual traces by identifying residual peaks.Finally,the forming processes of proposed methods were simulated by ANSYS/LS-DYNA finite element analysis software,and the profiles of forming were analyzed.At the same time,the actual forming experiments were carried out,and the above theoretical methods were further validated.