Adaptive shape control of laser-deposited metal structures by adjusting weld pool size

Abstract

Adaptive direct metal/material deposition process using a fuzzy logic-based controller LMD (Laser Metal Deposition) is a technique used to repair damaged components and directly form three dimensional structures. From the aspect of productivity, improvement of the shape accuracy of the deposit is required to reduce machining process after LMD. Objective of this work is to control the build-up shape by adjusting the weld pool size. Configurations of deposits made with various LMD process conditions were measured in cross section. In addition, the signal intensity of heat radiation, plume emissions and laser reflections from the weld pool was monitored by photodiodes intergrated in laser processing head during LMD process. The results showed a strong correlation between weld pool size and signal intensity of heat radiation. Adaptive shape control system, which consists of in process monitoring system and PID (Proportional-Integral-Derivative) controller using that correlation, was developed to control build-up shape. Due to the liner relationship with weld pool size, laser power was selected as the PID output parameter adjusted by the heat radiation signal. Since the target value of the heat radiation signal can be changed flexibly during the LMD process in our PID control system, deposit shape is successfully controlled as required with sufficient profile accuracy of the build-up layers. V C 2014 Laser Institute of America.

Advancements in 3D Printing: Directed Energy Deposition Techniques, Defect Analysis, and Quality Monitoring

“…The knowledge is pivotal in the development of real-time feedback control systems, ultimately enhancing the reproducibility of a microstructure. Miyagi et al [223] utilised a CCD camera equipped with three distinct photodiodes for Near-IR, IR, and Ultraviolet (UV) spectra measurement. By simultaneously tracking the deposition area, thermal radiation, and plume emission, they gained a comprehensive understanding of the deposition process, thereby optimizing efficiency by analysing the relationship between signal intensity from a molten pool and the shape of the structure formed under various conditions.…”

Review on adaptive control of laser-directed energy deposition

“…Qi et al 65 proposed an accurate quadratic regression transfer function to obtain a stable width by changing the laser power or scanning speed. Miyagi et al 51 developed an adaptive shape control system, which consists of a process monitoring system and a PID controller. In this system, the deposited shape is successfully controlled as required using the profile accuracy of the deposited layers.…”

Real-time closed-loop control of molten pool transient area in direct laser deposition via PID algorithm with enhanced robustness

“…Salehi et al [14] applied a PID controller with real-time proportional, integral and differential components to control the molten pool temperature during processing in real time. Miyagi et al [15] used photodiodes integrated in the laser processing head to monitor the thermal radiation, plume emission, and laser reflection signal intensity of the molten pool to obtain its size characteristics. A PID controller was then constructed to successfully control the morphology of the deposited layer.…”