Experimental investigations on the role of tool size in causing and controlling defects in single point incremental forming process

Abstract

Single point incremental forming is a cost-effective alternative of conventional stamping process. However, due to inadequate knowledge, the process has not yet been employed on industrial scale. In this study, the role of tool radius in causing and controlling development of defects in single point incremental forming is investigated. Throughout the course of investigations, AA1060 aluminum is used as the experimental material. Initially, a range of tests with tool radius (r) ranging from 1t(o) to 2.35t(o) (where t(o) is sheet thickness) are conducted. It is found that defects, namely, pillow, wall and material-fold, develop in a part if forming is performed with an unduly small tool (i.e. r<2t(o)). Furthermore, as a result of these defects, the part accuracy and sheet formability reduce. In the second stage, the effect of selected process parameters (i.e. feed rate, yield strength, wall angle, sheet thickness and step size) on the growth (or size) of aforesaid defects is examined. The test results reveal that the investigated parameters, excluding feed rate, are significant. In order to prevent inappropriate selection of tool and thus to simultaneously control all the defects, a least-radius limit is defined (i.e. r(l)), and as a last stage of investigations, its correlation with the short listed significant parameters is determined. To do so, a comprehensive design of experiments is performed. According to the design of experiment findings, the radius limit r(l) varies as a process parameter is varied. Moreover, this variation effect of parameters is highly interactive. Finally, an empirical formula to predict the said radius limit is proposed and its correctness is verified.