Development of sensing and control system for robotized laser-based direct metal addition system

Abstract

Laser-based direct metal addition (LBDMA) is a promising directed energy deposition technology that is well suited for the production of complex metal structures, low-volume manufacturing, and high-value component repair or modification. LBDMA is finding wide application in the automotive, biomedical, and aerospace industries. However, the process reliability and the repeatability of finished components are still problems. This work offers a solution by developing a sensing and control system for the robotically controlled 8-axis LBDMA system developed at the Research Center for Advanced Manufacturing of Southern Methodist University, Dallas, TX. The developed system consists of sensing and control units for the powder flow rate and the molten pool size. An optoelectronic sensor was developed to sense the powder flow rate. It is a main component in an on-line control system of powder flow rate in a LBDMA system. An infrared imaging setup was installed on the laser head to monitor the top full-field view of the molten pool. A simple proportional integral derivative (PID) controller, combined with feed-forward compensation was used to build a closed-loop control system for achieving a uniform molten pool size. Two L-shaped single-bead walls were built with and without closed-loop control, respectively. A good performance on achieving uniform geometry by closed-loop control of the molten pool size was approved.

Review on adaptive control of laser-directed energy deposition

“…Several researchers also monitored other signatures that may affect the final qualities, such as detection of particle-in-flight velocity with a diagnostic tool based on CCD camera 47 and monitoring of powder flow using a photoelectric sensor. 52 In general, cracks and pores are important symbols of defects in LDED and are difficult to monitor. The earliest attempt was to monitor cracks using acoustic emission sensors, 53,54 but it was easily affected by external interference in field monitoring.…”

Intelligent process planning and control of DED (directed energy deposition) for rapid manufacturing

“…On the other hand, in current CAM software, the deposition parameters remain constant during the entire process even though the required deposition amount can differ according to each tool path point. With respect to the last two requirements, such challenges can be better solved using real time monitoring and feedback control (Ding et al, 2016).…”

Skeleton arc additive manufacturing with closed loop control

“…Mazumder et al investigated closed loop during powder deposition. Ding et al [5] proposed in-situ monitoring to con-trol laser based direct metal addition moved with an eight axis robot system. Heralic [6] proposed to use 3D scanning to obtain the geometry of the layer and to compensate the difference in height with iterative learning compensation.…”