DEVELOPMENT OF 2D AND 3D LASER FORMING STRATEGIES FOR THIN SECTION MATERIALS USING SCANNING OPTICS

摘要

Laser forming offers the industrial promise ofcontrolled shaping of metallic and non-metalliccomponents for prototyping, the correction of designshape or distortion and precision adjustmentapplications. The potential process advantages includeprecise incremental adjustment, flexibility ofapplication and no mechanical 'spring-back' effect.However, the asymmetric nature of laser forming ofsheet material using conventional beam deliverymethods along multiple, continuous irradiation linesmeans that the energy input cannot readily beuniformly distributed across the work-piece, bothspatially and temporally, and each successive portionof the irradiation sequence is effectively being appliedto a part or surface of different shape to that earlier inthe sequence. Hence, a high degree of uniformity ofshape (curvature variation) in the resulting laserformed part can be difficult to achieve in practice. Theuse of scanning optics is therefore now beinginvestigated as a possible route to achieve a moreuniform temporal and spatial distribution of the laserenergy, by applying the laser energy in pulses andscanning the beam rapidly across the sheet surface. Inaddition, as the material thickness decreases itbecomes more difficult to induce high thermalgradients with conventional beam delivery methodsdue to speed limitations. Scanning optics allow highertraverse speeds and hence high thermal gradients inthin sheets and foils to ensure positive bending via theTemperature Gradient Mechanism (TGM).The work reported here centres on studies performedon a Nd:YAG laser marking system to investigate theapplication of pulsed laser energy delivered viascanning optics. Strategies developed for the 2D and3D laser forming of thin section materials arepresented. Online displacement measurements, postformingsurface contouring and metallurgicalinvestigations are included.