Multi-stage single-point incremental forming: an experimental investigation of thinning and peak forming force

Multi-stage single-point incremental forming (MSPIF) is used to form sheet metal parts of complex geometry with steep wall angles. The present paper describes an experimental investigation focused on part thinning and peak forming force acting on part formed by MSPIF. Four parameters, namely step depth, tool diameter, sheet thickness and initial wall angle, are considered to study their influence on part thinning and vertical component of forming force. Experiments are designed on the basis of central composite design of response surface methodology, and results are analyzed using analysis of variance. It is found that initial wall angle is the most significant parameter for thinning followed by sheet thickness. Thinning decreases with decrease in initial wall angle and increase in sheet thickness. For peak forming force, sheet thickness is found most significant parameter followed by tool diameter, step depth and initial wall angle. It decreases with decrease in all four process parameters. Further, regression models of thinning and forming force are developed. Optimization of process parameters is also performed to minimize thinning and forming force.