Development of 2D and 3D laser forming strategies for thin section materials using scanning optics

Laser forming offers the industrial promise of controlled shaping of metallic and non-metallic components for prototyping, the correction of design shape or distortion and precision adjustment applications. The potential process advantages include precise incremental adjustment, flexibility of application and no mechanical ‘spring-back’ effect. However, the asymmetric nature of laser forming of sheet material using conventional beam delivery methods along multiple, continuous irradiation lines means that the energy input cannot readily be uniformly distributed across the work-piece, both spatially and temporally, and each successive portion of the irradiation sequence is effectively being applied to a part or surface of different shape to that earlier in the sequence. Hence, a high degree of uniformity of shape (curvature variation) in the resulting laser formed part can be difficult to achieve in practice. The use of scanning optics is therefore now being investigated as a possible route to achieve a more uniform temporal and spatial distribution of the laser energy, by applying the laser energy in pulses and scanning the beam rapidly across the sheet surface. In addition, as the material thickness decreases it becomes more difficult to induce high thermal gradients with conventional beam delivery methods due to speed limitations. Scanning optics allow higher traverse speeds and hence high thermal gradients in thin sheets and foils to ensure positive bending via the Temperature Gradient Mechanism (TGM).The work reported here centres on studies performed on a Nd:YAG laser marking system to investigate the application of pulsed laser energy delivered via scanning optics. Strategies developed for the 2D and 3D laser forming of thin section materials are presented. Online displacement measurements, post-forming surface contouring and metallurgical investigations are included.Laser forming offers the industrial promise of controlled shaping of metallic and non-metallic components for prototyping, the correction of design shape or distortion and precision adjustment applications. The potential process advantages include precise incremental adjustment, flexibility of application and no mechanical ‘spring-back’ effect. However, the asymmetric nature of laser forming of sheet material using conventional beam delivery methods along multiple, continuous irradiation lines means that the energy input cannot readily be uniformly distributed across the work-piece, both spatially and temporally, and each successive portion of the irradiation sequence is effectively being applied to a part or surface of different shape to that earlier in the sequence. Hence, a high degree of uniformity of shape (curvature variation) in the resulting laser formed part can be difficult to achieve in practice. The use of scanning optics is therefore now being investigated as a possible route to achieve a mor...