Research On Generating Method Of Machining Track Of Five-axis Incremental Sheet Forming Tool And Influence Of Angle Of Heel

The incremental sheet forming process is a new forming technology without mold,which has the advantages of small-batch manufacturing,good shaping capability,and high automation.It is applied widely in small-batch manufacturing,multi-type research and development,and individualized production.As a new processing technology,the deep study of the five-axis incremental forming technology has become one of the important topics in this field.This paper presents a generating method for the machining track of the five-axis incremental forming tool.The generating steps are as follows: establishing the geometric shapes of the formed workpiece,obtaining the center surface of the tool head by offset,outputting STL files,slicing STL files,extracting the intersection line of each layer,calculating the axial direction of the tool according to the normal direction of the facet or directing to a point,and outputting the tool endpoint locus and the tool axis vectors.The tool path can realize three different processing methods of tool axis normal,tool axis inclination fixed,and tool axis directing fixed point.The detailed algorithm for each step of tool machining track generation is given,and the spatial transformation of tracing points in the relevant steps is deduced.The five-axis incremental forming tool machining track creating system is developed,and the feasibility of this method is verified by experiments.Furthermore,the angle of heel introduced by the five-axis incremental forming was studied by numerical simulation,and the influence of the different angles of heel on equivalent stress,strain,thickness,and deformation force of workpiece is analyzed.The results show that the equivalent stress distribution of the workpiece with different angle of heels is relatively uniform,and the influence on the equivalent stress is small.The main strain and reduction ratio state of the workpiece with different angle of heels are close,and the strain state tends to the plane strain condition;The average thickness of the workpiece decreases with the increase of angle of heel,and the thinning is the most serious for the same workpiece thickness distribution above the middle position,which is verified by experiments.With the increase of the angle of heel,the axial and radial deformation forces of the workpiece decrease.For the tangential deformation force,there is no obvious change,and the overall deformation force decreases.The influence of the angle of heel on the sheet metal formability was studied through the variable angle cone cup experiment.The forming performance of the five-axis incremental forming is tested by forming a limit angle based on the depth of processing when the workpiece is broken.The results show that the forming performance of the fiveaxis incremental forming workpiece is higher than that of the three-axis incremental forming.With the increase of angle of heel,the forming limit angle increases,and the forming performance of the workpiece increases.At last,the influence of the different angles of heel on the workpiece surface quality is studied by measuring the surface roughness(Ra)of the workpiece.The results show that the surface roughness decreases first,then tends to be stable,and finally increases with the increase of angle of heel.Reverse engineering was used to study the influence of the different angles of heel on the forming precision of the five-axis incremental forming.The standard deviation was introduced to compare the actual workpiece size and the theoretical workpiece size.The results show that the standard deviation of the workpiece decreases first and then increases with the increase of the angle of heel.Compared with three-axis incremental forming,the five-axis incremental forming has the better surface quality and forming precision.