Closed-loop blow forming: direct reuse of trimming scrap for new component manufacture

In this work, the direct reuse of scrap from the addendum region of previously blow-formed aluminium sheets to manufacture smaller components through a secondary forming step was studied. Numerical simulations and experimental tests were conducted to assess the feasibility of the approach and to evaluate the behaviour of the pre-deformed blank and the thickness distribution of the secondary components. After primary forming, the selected scrap region exhibited less than 6% thinning and a maximum equivalent plastic strain of 0.11. The results showed that components produced from reused material exhibited thickness distributions comparable to those obtained from virgin sheet, with an average pointwise difference of approximately 3%. From an environmental perspective, the proposed closed-loop blow forming solution enabled substantial energy savings by avoiding the production of new sheet stock and the associated material-processing operations. The cradle-to-gate assessment showed that the scrap-based route reduced cumulative energy demand by 77% and global warming potential by 83% compared with the virgin-sheet route. These findings demonstrated that direct reuse of blow forming scrap via secondary forming can produce components with thickness distributions comparable to those obtained from virgin sheet while substantially reducing environmental impacts.