Investigation On The Hole Incremental Flanging Process

The sheet metal numerically incremental forming process is a flexible processing,which is point by point through a digital control device using a pre-programmed control program.Applying incremental forming technology to hole flanging adapt to the development and renewal of new products without expensive die.However,there are still some problems in incremental flanging,such as inadequate processing accuracy and uncontrollable forming performance In this paper,the effects of processing factors,lubrication factors and material factors on incremental flanging process with three passes of change angle were experimentally studied,after that,the effects of process parameters on the forming accuracy and formability of incremental flanging parts were analyzed.The results show that:1)Distribution of deformation per pass in three-pass hole incremental flanging with change angle has a significant effect on flanging accuracy.In the limit forming angle,the initial forming angle is found to decrease as the spring back increase.The spring back of the previous pass can be effectively part eliminated by the latter pass forming,and the effect is more obvious as the deformation of the latter pass is larger.In a word,when multi-pass incremental forming flanging,the last pass must ensure a certain amount of deformation in order to effectively overcome the inadequacy of precision in the pre-forming process and improve the flanging accuracy.In the process of three-pass incremental flanging with change angle,the pass distribution of40-65-90 can form parts with high precision and uniform wall thickness.The actual flanging diameter is smaller than the target theoretical diameter when the depth increment is 0.3 mm.Only when the depth increment is large enough to be 1.0 mm,the actual flanging diameter is larger than the target part diameter.These finding lead to a conclusion that the flanging parts with high precision,good surface quality,uniform wall thickness and high forming height can be formed by the depth increment is 0.3-0.5 mm,the diameter of tool head is 10-12 mm,and the feed speed is about1000 mm.min^-1.2)The forming quality of three-pass hole incremental flanging parts is related to the material performance parameters.The shape accuracy of incremental flanging parts with high strength,large elongation and large enlargement is prone to negative deviation,and the maximum thinning rate is low,and the surface roughness of flanging parts is large.For 5A02 and 5182 aluminium alloys with lower strength and elongation,the shape accuracy of progressive flanging parts is prone to positive deviation,further,the maximum thinning rate of flanging parts formed by 5A02aluminium alloy sheet and the surface roughness is larger as the elongation,strength and hole enlargement is smaller.3)Three-pass hole incremental flanging of SUS304 stainless steel with change angle by small tool head diameter,because the contact area between sheet metal and tool head is small and the deformation is concentrated when the tool head diameter is small,and the smaller tool head stiffness is poor.The material is easy to accumulate on the vertical plane with the tool head axis because of the large force on the vertical plane with the tool head axis,which results in the sharp thinning of the contact area and the concave formation,which leads to the failure of the progressive extrusion process.It’s supposed that add a small angle of pre-deformation to reduce the angle between tool head and sheet metal and increase the shear force,then form successfully.