A camera based control method of deposition bead width in laser powder deposition process

Laser powder deposition is an additive manufacturing process that can be applied to fabricate complex components or repair worn parts. The process is sensitive to the variations of the governing parameters or unexpected disturbances, which may lead to the geometric fluctuation of the deposition bead. In this work, a closed-loop control system is developed to improve the geometric accuracy of the LPD process. The laser power is selected as the control variable. In order to control the accuracy of the deposition bead width, a CMOS camera is used to measure the bead width in the real time. The CMOS camera captures the images of molten pool and then an image process algorithm extracts the bead width from those images. The controller constitutes of a feedforward controller and a feedback controller which is a traditional PID controller. Based on the experimental data, a dynamic model of the process is developed with the system identification method. According to the simulation results, the closed-loop control system we have established can improve the reference tracking and disturbance rejection performance of the system, thus improve the geometric accuracy of the process. The performance of the controller is verified experimentally by building walls with constant and varying width. Also, the controller is applied to the repair of compressor blade tip which has a varying width.