Height control in GMA-AM using external wire as controlling variable

Gas metal arc additive manufacturing (GMA-AM) is gaining great attention to produce large-scale parts owing to its merits of low device investments and high deposition rates. Despite this fact, a robust control system for deposition height in thin-walled parts is yet to be developed due to the lack of an appropriate controlling variable. This study attempts to propose an external wire-based GMA-AM technique to solve this issue. The influences of arc current, travel speed, and external wire feed speed (EWFS) on layer geometry were studied. It is indicated that the EWFS exhibits a greater influence on the layer height of thin walls than the arc current and the travel speed. The nozzle to the top surface distance (NTSD), monitored via a vision sensor, was extracted by Median filter, Sobel algorithm, Canny algorithm, and Hough transform. The dynamics between the NTSD and the EWFS were established via a nonlinear model. A parameter self-tuning fuzzy controller was designed to control the NTSD via changing the EWFS. System simulation tests and control tests were performed to validate the robustness of the parameter self-tuning fuzzy controller.