Developments towards controlled three-dimensional laser forming of continuous surfaces

There has been a considerable amount of work carried out on two-dimensional laser forming, using multipass straight line scan strategies to produce a reasonably controlled bend angle in a number of materials, including aerospace alloys. However, in order to advance the process further for realistic forming applications and for straightening and aligning operations in a manufacturing industry it is necessary to consider larger scale controlled three-dimensional (3D) laser forming. The work presented in this article uses a predictive and adaptive approach to control the 3D laser forming of a 1.5 mm mild steel sheet into a desired continuous surface. The surface considered in the study was the pillow (or dome) shape. Key to the control of the process was the development of a predictive model to give scan strategies based on a required geometry. The forming rate and distribution of the magnitude of forming across the surface were controlled by the process speed. When the geometry is not formed within one pass, an incremental adaptive approach is used for subsequent passes, utilizing the error between the current and desired geometry to give a new scan strategy, thus any unwanted distortion due to material variability can be accounted for.