On the forming uniformity during a single layer forming of electromagnetic incremental forming

Abstract

Aiming to the precise control of forming quality in electromagnetic incremental forming (EMIF), deformation behaviors of a spherical crown-shaped thin-walled workpiece during a single layer forming of EMIF are analyzed by means of numerical simulation. The influences of the coil overlap ratio, coil moving strategy, and discharge voltage combination on the forming uniformity of the workpiece are revealed. The maximum electromagnetic force and forming depth represent a “dramatic decrease–long-term steady–moderate decrease” variation over the increase of discharge time for forming a single layer by sequential discharging. The difficult-to-deform region located outside the overlap region of coil positions deforms insufficiently, leading to poor overall uniformity. Better uniformity and higher forming efficiency are achieved by sequential discharging compared with interval discharging. With an increase in the coil overlap ratio, the circumferential uniformity of the workpiece is improved because the transition deformation region is reduced and the active deformation region subjected to electromagnetic force is increased. In addition, the forming uniformity of the workpiece can be improved significantly by an optimized discharge voltage combination with properly decreased first discharge voltage and increased last discharge voltage, respectively. A forming scheme for a spherical crown-shaped thin-walled workpiece is proposed based on the forming principles and a workpiece with high precision and good uniformity is obtained. Therefore, EMIF is demonstrated as capable to form high precision large-size thin-walled parts.