From Machine Enclosure to Pressurised Build Chamber - Enabling Additive Manufacturing of Large Components in Inert Environments

Sammanfattning

Additive manufacturing (AM) of large titanium components for the aerospace industry requiresinert environments to prevent oxidation and contamination to ensure material integrity. As theaerospace manufacturers scale up titanium AM, maintaining these inert atmospheres becomesincreasingly challenging. Permanova Lasersystem AB is developing a scaled up laser directedenergy deposition (L-DED) system with a larger and reversible build plate to enable larger andmore efficient builds and improved residual stress control. However, the current tent-based inertenclosure cannot be expanded to work with the new build plate. This thesis explores howthe existing laser safety enclosure surrounding the system can be adapted to also function as anoverpressurised inert enclosure by assessing what overpressure it should withstand and maintain,how it responds to it, what the biggest problems for maintaining it are, and how differentsolutions for solving those problems compare. Interviews, standards review and state-of-theartanalysis established that a pressure differential of 50 Pa prevents ambient air infiltration;therefore, 100 Pa was selected as the design pressure to incorporate a safety factor of two andmaintain recommended engineering margins.Leakage assessment revealed critical leakage paths at the floor interface, ceiling, corners, andpanel joints, while structural simulations identified weaknesses in the active protection panelsand part of the skeleton. Based on these findings, sealing and reinforcement concepts were developedand evaluated. The final solution was to implement metal plates and L-profiles togetherwith a polyurethane sealant for covering the major leakage paths, a fully sealed active panel tonot only prevent leakage but also to increase stiffness and an additional roof beam to eliminatedeflection. The results demonstrate that the existing laser enclosure can effectively be adaptedinto a large, overpressurised inert enclosure without extensive redesign.