Development of a laminar flow local shielding device for wire + arc additive manufacture

•Determined the environmental contamination levels required for protecting AM parts.•A new local shielding was developed which provides laminar flow.•Experimental comparison of the laminar shielding device with a conventional device which showed three orders of magnitude improvement in the contamination levels.•Evaluation of laminar shielding device performance with a mock-up AM wall which showed that it could be protected up to 30 mm from the top.•A CFD model was used to evaluate the benefits of applying an argon knife.

A shielded environment is required during the wire + arc additive manufacture (WAAM) of titanium alloys to prevent oxidation. Applying local shielding can increase the flexibility of the WAAM process, however conventional devices do not provide adequate protection due to entrainment of the surrounding air. In this study, a new local shielding device based on laminar flow was developed and compared with a conventional device. The laminar local shielding device showed up to three orders of magnitude improvement with contamination levels below 2000 ppm being achieved with a stand-off distance of 30 mm. The performance was also assessed along a mock-up WAAM wall which showed that it could be protected up to 30 mm from the top. Finally, computational fluid dynamics models provided insight into the device performance and enabled the performance of an argon knife to be evaluated.