Tool Stiffness Calculation in Roll Forming

Abstract

In roll forming a metal sheet is incrementally bent at room temperature through numerous pairs of opposing forming rolls. The shafts equipped with rolls represent the most compliant assemblies in the whole roll forming mill. The shafts of one forming pass have to be aligned in the right position, relative to each other and the next as well as the prior forming pass, to avoid defects and to ensure profile dimensions which fulfil the geometric requirements. The forming forces vary greatly, depending on the roll set geometry, settings and stiffness of the individual forming passes. These forming forces lead to deflections of the shafts equipped with rolls, which need to be compensated. In this paper, a finite element model with hexahedron elements of the shafts equipped with rolls is developed, in order to determine its load-deflection behaviour. The accuracy of the model is validated with the aid of experimental data. The provided model shows high accuracy compared to the experimental data and no systematic error over the tested load range is observed. Additionally, the nonlinear stiffness behaviour is investigated in detail to understand the occurring nonlinear effects. (Received in September 2020, accepted in November 2020. This paper was with the authors 1 week for 1 revision.)