Evaluation and optimisation of micro flexible rolling process parameters by orthogonal trial design

As the strip thickness is in the range of sub-millimetre in micro flexible rolling, springback ratio in thickness direction has a significant impact on product quality, which is influenced by various process parameters during forming process. This paper focuses on performing a numerical and experimental investigation to evaluate the effects of initial strip thickness, friction coefficient and rolling speed on the springback ratio in thickness direction during the micro flexible rolling process with reductions of 20 to 50% using orthogonal trial design, and wherein the three-level factors orthogonal array is chosen and nine representative orthogonal trials for each reduction have been implemented. With the significance of each process parameter for each reduction identified by variance analysis, an optimum proposal for each reduction to obtain the minimum springback ratio has been determined numerically, which is afterwards confirmed by experimental data. Moreover, a qualitative estimate of the influences of process parameters on the rolling force, as well as a quantitative analysis of the relationship between the length of thickness transition zone and the parameter level have also been carried out with reference to the obtained results.