Research On Springback Control And Compensation For Stepped Feature And Open Feature Sheets On Isf

Incremental Sheet forming(ISF)is a new die-less and flexible forming technology,which is suitable for small batch production of complex sheet metal parts.Compared with conventional stamping,the development of ISF is limited by the low geometric accuracy.How to reduce the geometric deviation of complex parts formed by ISF is the research emphasis in the field of ISF at present.With the support of National Natural Science Foundation of China(Grant #1737210),the investigations on geometric accuracy of parts with stepped feature or open feature formed by ISF has been studied.The research to improve geometric accuracy in this work mainly involves the following three aspects: process parameters optimization,optimization of multi-pass ISF(MSIF)path and geometric compensation.The achievements of this work are of great significance for improving geometric accuracy of complex parts formed ISF.The key conclusions are summarized as follows:Orthogonal experiments and ANOVA were conducted to study the influence of tool diameter,step down,feed rate and rotational speed on geometric accuracy of parts with stepped feature.The combination of optimized parameters was: tool diameter as D5 mm,feed speed as 3000mm/min,and step down as 0.15 mm without tool rotation.The reasonable intermediate configurations during MSIF were designed based on CAD model and geometric deviation.The basic design criterions of stepped feature parts are summarized as follows:Firstly,the stepped flank should be formed precede stepped plane.Secondly,the optimal angle for the transition between the stepped flank and the intermediate side wall shall be more than 20°.Finally,the tool should be far away stiffness region.The new forming strategy reduced the geometric deviation by 50% compared with that of SPIF.The optimized tool path considering compensation during MSIF further decreased the geometric deviation by 30% compared with that of MSIF without compensation.The sectional profile of the part formed by MSIF with compensation is basically consistent with CAD model.Better geometric accuracy and surface quality of part with open feature can be obtained using contour toolpath compared with that using Zigzag toolpath.Parts formed by flat head tool had better geometric accuracy and roughness quality than that formed by ball head tool while keeping the same diameter of tool.Along with the decrease of wall angle,the geometric deviation of open feature parts increased gradually along the radial and vertical direction after the parts unclamped.When the forming angle is less than 20° for the open feature parts,multi-pass incremental forming was applied to improve geometric accuracy.The first pass was used to forming middle area by contour toolpath.The subsequent passes were used to forming the other area by in-to-out toolpath.MSIF has increased the plastic deformation and reduced the geometric deviation in the side wall and height direction after unclamped.