Investigation into the numerical model behaviour of Belleville washers in cold roll forming

With the steadily increase in demand for roll formed products due to their application for fields such as automotive, construction, architecture, etc., roll forming companies are challenge with rising customer demands. Companies are struggling to bring a product through from design to manufacture at improved rates, whilst achieving tighter tolerances. The roll forming process may also induce undesirable forming defects such as twist, distortion and straightness problems.Traditionally these issues would be resolved through an empirical approach which heavily relies on the designer's expertise and intuition. This approach can increase undesired development costs due to materials wasted and time delayed. Over the years, numerical simulations have been deployed to try and geometrically validate these defects and ultimately reduce the development phase of a product. The designer has the capability to virtually investigate changes in specific parameters without the risk of expensive tooling costs. The industry partner of this project, Hadley Group, Birmingham, implement Belleville washers into the roll tool configuration. The purpose of these washers is to apply pressure to the strip during roll forming in order to drive material through each forming station. They are also used to adjust the gap between the top and bottom forming rolls, since the incoming material gauge can vary by the nominal tolerance values from coil to coil. For the purpose of this paper, an investigation is carried out focusing on an individual parameter within the finite element analysis (FEA) of the cold roll forming process, i.e. the 'unknown' spring acting on the top roll during the forming process due to the implementation of Belleville washers in the pillar set up. The work explained in this paper shows the eects of the pressure applied to the forming process on the geometric attributes of the section being formed. The outcome will determine the viability of this parameter, which may ultimately require the numerical design methodology of roll formed products to be amended accordingly.