A critical analysis of formability and quality parameters for forming a dome shape using multi-stage strategies in incremental forming process

Abstract

In the present work, the effect of different forming strategies on material flow in incremental forming of hemi-spherical dome shaped components is investigated. During single stage forming strategy the part has failed at 10 mm depth from the entrance of hemi-spherical dome due to steep wall angle. To overcome this problem, the sheet is deformed by adopting two different multistage forming strategies. Both these strategies have four stages with different intermediate shapes. In the first strategy, the intermediate shapes are modelled as cones with different heights and wall angles. In the second strategy, the intermediate shapes are modelled as domes with different radius of curvature and height. Even though the sheet is formed successfully in both multistage forming strategies, it is found that the intermediate shapes have significant effect on forming limits, geometric accuracy and manufacturing time. The accuracy of dome formed using first strategy is found to be deviating from the desired shape due to formation of stepped features, which has overcome by implementation of second strategy. In addition, a new theoretical model is proposed to predict the thickness of the sheet during the multi-stage forming based on the volume consistency approach. The FE simulations are also performed to study the forming behaviour in both single stage and multi-stage forming. Various quality parameters found from FE simulations such as thickness distribution, forming forces and geometrical accuracy are in agreement with the experimental results.