A parametric study on the accuracy of bending in micro W-bending using Taguchi method

High dimensional accuracy of micro-bent parts, particularly the desired bent angle, is often required. In the study reported in this paper, a micro W-bending process was used for the study addressing this issue. Four main parameters affecting the bending accuracy of the micro W-bent parts were considered: foil thickness, grain size, foil orientation and punching frequency. Based on Taguchi L8 orthogonal array (OA), a micro-sheet-metal forming machine equipped with W-shaped punch and die was used to conduct the micro W-bending experiments. The experimental results were analyzed using signal-to-noise (S/N) ratio and the analysis of variance (ANOVA). It was identified that the extent of the effect by these parameters on the micro W-bending process depends on springback behaviours. The foil thickness had highest influence on the springback amount of the bent parts. However, the negative springback was influenced mostly by the grain size, closely followed by the foil thickness. Furthermore, the optimum bending conditions for different types of the springback were obtained. Confirmation experiments were then performed not only to validate the improved bending accuracy but also to verify the extent of the contribution from each parameter to the amounts of the springbacks. Finally, mathematical models for both, positive springback and negative springback, were developed using the regression analysis. It was observed that the predicted values fit well with the experimental results, indicating the adequacy of the established models.