Feedback control of variable width in gas metal arc-based additive manufacturing

Abstract

Gas metal arc additive manufacturing (GMA-AM) is one of the most promising methods to produce large-scale complex metal parts by melting metal wire layer by layer. Nevertheless, this process is prone to be affected by various disturbances and requires online monitoring and feedback control. This study aims at fabricating variable-width components in which layer width in the same layer is changeable in GMA-AM via an in-situ monitoring and control system. A passive vision sensing system, composed of a camera and a biprism, was designed to extract the layer width in real-time via the procedures of camera calibration, image correction, molten pool extraction, and molten pool edge reconstruction. A fuzzy controller was designed by adjusting the arc current to maintain the expected layer width. The controller's performance was verified by performing inter-layer temperature and travel speed disturbance tests. Two 20-layered variable-width walls were built, and the results demonstrate that the passive vision sensing and feedback control system can significantly improve the layer width stability.