Effects of Unbalanced Forces on Product Thickness Accuracy in Multi-rollers Flow-Forming

An advantage of the flow-forming process is high accuracy of products. Most researches have studied product diametric accuracy, but they have rarely investigated thickness accuracy. In this paper, a procedure is proposed to predict the effects of unbalanced forces on the product thickness accuracy. For this purpose, affecting parameters on roller forces were distinguished and roller forces were assumed as functions of these parameters. Noting that during the process, affecting parameters only change with mandrel deflection, these parameters (and consequently rollers forces) were calculated as functions of mandrel deflections. Function's coefficients were calculated using finite element method. Considering the force equilibrium of rollers and mandrel and using the above-mentioned functions,the mandrel deflection was calculated. Consequently, product thickness error due to mandrel deflection was calculated. Experiments were also performed to validate the proposed theory. Theoretical and experimental thickness variations follow similar trends. Finally, it was demonstrated that unbalanced forces cause non-uniform thickness along the product's length.