Path Generation Of Single Point CNC Incremental Forming

At present,the constant process parameters are used to generate the machining path in the CNC incremental forming,and the complex sheet parts can not fulfill the requirements of the users.In this paper,aiming at the influence of CNC incremental forming parameters on the forming quality,a new forming path generation method is proposed to improve the forming quality and formability of the complex shape sheet part,which play an important guiding role in the future industrial extension.Firstly,considering the influence of layer distance on the quality for CNC incremental forming,a method to generate the counter path with unequal layer distance for different curved regions of forming angle was proposed,which based on the constant scallop height.First,the forming path with constant scallop height was generated;then,the contour path was inserted in to the region with large forming angle and large layer distance so as to further optimize the layer distance.Then,the forming path was generated,which could both meet the requirements of scallop height and reduce the forming force and the springback deformation.Secondly,aiming at the problems of CNC incremental forming based on constant feed rate,an unequal feed rate determination algorithm based on adaptive surface features and a finite element method based on unequal feed rate was proposed.The volume change rate threshold is obtained from the average volume change rate of the sheet volume involved in the forming sheet and the volume change rate between the adjacent two path points,and then the feed rate between the adjacent path points was determined by the threshold value.Thus for sheet parts with complex shape,can be forming according to the shape features of sheet parts,generating different feed speed of the different forming angle region,and further improve the formability and the forming quality under the same forming efficiency.At the same time,the distance between the two adjacent path points and the determined feed speed is given.The time points of the extrusion tool head at each path point are obtained,and the method of CNC incremental forming finite element analysis based on the unequal feed speed is carry out.Thirdly,aiming at the problem that it is difficult to choose the suitable size of the extrusion tool head for forming the complex shape sheet parts in CNC incremental forming,this paper presented a CNC incremental forming method for multi-diameter extrusion head of surface division.The method is cutting inner surface of formed sheet parts with the horizontal plane,extracted the triangle facet which intersects with the horizontal cutting plane.The extracted triangular facets are divided into numerous small forming surfaces according to their position relations with the horizontal cutting plane,calculated the curvature of each small forming surface in the model.When there is not only one contour line on the same height,we can calculate the minimum distance between contour lines by judging the location relation between contour lines,and then the radius of extrusion tool head is determined.Through divided the radius of curvature into intervals,the forming surface is divided into different forming regions,and the extrusion tool head with different diameters are used for CNC incremental forming in different forming regions,and the CNC incremental forming path of multi-diameter extrusion tool heads is generated.Finally,based on the ANSYS/LS-DYNA finite element analysis software and the forming experiment,the validity of the forming path in CNC incremental forming is verified.