Gap-detecting sensor and wire feed control in butt laser welding with filler wire

Abstract

To guarantee good quality of butt laser welding with filler wire, a sensor, that is used to detect gap width and seam tracking and a wire feeding system have been developed in this paper. The sensor contains a laser diode as assistant optical source and a photoelectric cell as receiving component. A step-motor drives the sensor transversally scanning above the work piece so as to detect the gap width as basis of adjusting welding parameters and the center position of the butt gap as benchmark of seam tracking. A computer calculates the required wire feeding speed and welding speed according to the gap width and transfers these values to wire feeding system and speed adjusting system. In the welding of 2mm-thick low carbon steel sheet, the wire feeding speed and welding speed are respectively changed according to gap width detection and weld bead appearance is analyzed. The results show that it is better to adjust wire feeding speed for narrower gap and adjust welding speed for wider gap. According to the detected signal of the sensor, the appearance quality of the total weld could be guaranteed by choosing wire feeding speed or welding speed as the control variable for different gap widths.