Experimental and Numerical Analysis of Roller Leveler Straightening for Coiled Bar and Wire

Straightening has been widely used to the industry for bars and wires to remove or change curvature, such as a cast or helix (curved and twisted) of coiled bars, produced by the wire rod rolling or wire drawing process. Roller leveler straightening is one of the most popular methods on straightening wires or coiled bars. Recently, required straightness for parts of such as automobile and precision apparatus has been getting higher. But higher straightness was not able to achieved by roller leveler, and it was considered whether there was a limit in the straightening technology. The purpose of this study is to investigate roller leveler mechanism by numerical and experimental analysis. The limit value of straightness was found only when coiled bar was straightened. The limit value of straightness was caused by the 3-dimensional shape of coiled bars (curved and twisted) and the tilting of bars during straightening. The numerical results by FE analysis on straightness and tilting of bar are good agreement with the experimental ones. Therefore, the numerical analysis is promising tool for estimating the limit value of straightness and bar tilting. From the numerical and the experimental analysis, initial shape of curved and twisted coiled bar is main factor causing bar tilting.