Machine Vision Based Real-Time Control of Metal Transfer in Laser Enhanced GMAW

In the laser enhanced gas metal arc welding (GMAW) process developed recently, droplets of melted metal can be detached from the wire under relatively low currents with the assistance of an auxiliary force provided by a laser. The stability of the arc and the quality of the resultant welds are improved. To compete with the gas tungsten arc welding (GTAW) of the much lower productivity in joining precision, the size of the droplet can be pre-defined and be controlled to meet the requirements from different applications. For this purpose, a machine vision based control system is developed to control the metal transfer in the laser enhanced GMAW process, the growth of the droplets are monitored by a high speed camera on-line and the size of the droplets are measured by an image processing algorithm at 500 frames per second in real time, when the droplets grow to the desired size, they are then detached with the help of the auxiliary force provided by the laser. A model prediction based droplet growth model has also been proposed to make the decision of when to apply the laser to detach the droplets. Experiments are done to verify the image capturing and processing abilities of the machine vision based control system. Also, simulations results show the effectiveness of proposed the droplet growth model.