Simultaneous Control of Penetration Depth and Bead Height by Controlling Multiple Welding Parameters

One of the important subject in the study of automatic arc welding is to establish control system of welding parameters for controlling bead shape, namely penetration depth, bead width and bead height, by detecting or predicting behavior of molten pool owing to change of groove shape. This report describes the study of simultaneous control system of penetration depth and bead height despite the variation of root gap in gas metal arc welding with X-groove. In this system, root gap width is detected by image processing with CCD (charge coupled device) camera, and welding current and welding speed are controlled in order to keep constant penetration depth and bead height. Furthermore in this system, wire feeding rate and terminal voltage are controlled by using equations proposed by Lesnewich and Halmφy so that both wire extension length and arc length can be kept constant during torch height control with ACC method. This control of both wire extension length and arc length is very efective to maintain stabilized welding arc. From the result of an experiment with X-groove of SUS304 stainless steel, both penetration depth and bead height can be simultaneously controlled to be almost constant despite the variation from 0 to 3 mm of root gap width.