A New Method for Calculating the Error Term Used in 2D Feedback Control of Laser Forming

Abstract

Laser forming of sheet metal has the potential to add to the growing repertoire of laser processing. This is of particular interest for flexible manufacturing and rapid prototyping. A factor limiting the practical use is the planning of the process parameters, such as laser scan path, laser power, laser scan speed, laser spot size, dwell time, etc. This study presents a new method for calculating the error between the target shape and the current shape. The method is based on geometrical information and uses a projection of the second derivative of the target geometry unto the current geometry. By comparing the projected second derivative with the second derivative of the current geometry, the error can be calculated. Once the error has been found, a feedback control strategy can be used to update the process parameters. The new method entails that the error can be calculated without having to solve the large scale mechanical FEM as part of the planning process. This reduces the planning time and enables a simpler approach that, for the error calculation, is independent of material properties. The method is verified for a 2D feedback system for simple bends in sheet metal, using FEM simulations of the laser forming process.