Control Of Weld Shape For Stainless Steel During GTAW Based On Laser Vision Sensing

Weld shape is one of the important factors that affect welding quality, welding parameters should match joint figure to attain good shape formation. It is the operator that adjusts welding parameters manually to fit the dimensional change of groove on traditional welding equipment, while it is difficult to make adjustments in real time and repeat the adjustment. By utility of laser sensor, we can solve the above problem by rectifying welding parameters according to the detecting result of the sensor. The technique of control of weld shape for stainless steel during GTAW based on laser vision sensing is studied in this paper.A MDK based weld feature detection system is established at first. A set of image processing algorithms, including median filter, threshold segmentation, improved gray weighted centroid algorithm and linear interpolation are used to extract stripe centerline from the original laser image according to its characteristic, and then slope-analyzing method is utilized to get feature points of the centerline. The points are calibrated to get their world coordinates, then weld geometric features of the groove are calculated and digital filter is used to deal with the results. Experiments show that the system is of good reliability and accuracy.Then a control system for welding parameters is designed, consisting of USB2813A, isolator, relay, et al. Welding current, wire feed rate and welding speed are selected as the controllables based on the property of GTAW, welding source, wire feeder, travelling gear are refit to be controllable, switch signal output from USB2813A can control welding process, voltage analog can control the value of each controllable, and they are calibrated to get the relationship between voltage output and each controllable. Effects of the three controllables on weld formation are analyzed, and looking-up table scheme is selected from the practical view, to change the controllables, then the optimal welding parameters for 304 stainless steel of different groove size is obtained from experiments, thus a welding parameters table is established.Finally, based on modularization, system software is designed by C++ language. Welding of workpieces with variable groove section are implemented by both the developed system and conventional welding method, comparison of experiment results shows that the system can adjust welding parameters with the size change of groove, thus controls weld shape by melting proper amount of metal.