Adaptive shape control of laser metal deposition by adjusting weld pool size

Abstract

Laser Metal Deposition (LMD) has been developed for repair of damaged components and for the direct forming of three-dimensional structures. From the aspect of productivity, shape accuracy of the deposit must be improved to shorten the machining process after LMD. The objective of this work is to control build-up shape by adjusting weld pool size. Configurations of deposits made with various LMD process conditions were measured by cross sectional observation. In addition, signal intensity of heat radiation, plume emission and laser reflection from weld pool were monitored by photodiodes integrated in a laser processing head during the LMD process. The results showed strong correlation between weld pool size and signal intensity of heat radiation. An adaptive shape control system, which consists of an in-process monitoring system and Proportional-Integral-Derivative (PID) controller using that correlation, was developed for controlling build-up shape. Due to the linear relationship with weld pool size, laser power was selected as a PID output parameter adjusted by heat radiation signal. Since the target value of heat radiation signal can be changed flexibly during LMD process in our PID control system, deposit shape is successfully controlled as required with sufficient profile accuracy of build-up layers.Laser Metal Deposition (LMD) has been developed for repair of damaged components and for the direct forming of three-dimensional structures. From the aspect of productivity, shape accuracy of the deposit must be improved to shorten the machining process after LMD. The objective of this work is to control build-up shape by adjusting weld pool size. Configurations of deposits made with various LMD process conditions were measured by cross sectional observation. In addition, signal intensity of heat radiation, plume emission and laser reflection from weld pool were monitored by photodiodes integrated in a laser processing head during the LMD process. The results showed strong correlation between weld pool size and signal intensity of heat radiation. An adaptive shape control system, which consists of an in-process monitoring system and Proportional-Integral-Derivative (PID) controller using that correlation, was developed for controlling build-up shape. Due to the linear relationship with weld pool size, las...