Sensor for automated front face weldbead area control

Abstract

A front face area control system has been develop for DC-pulsed tungsten inert gas (TIG) welding. The system is based on a binary vision system built to interface to the BBC range of microcomputers. The system utilizes a fast charge coupled device (CCD) camera, to enable an image of the weld surface to be captured during a 3 ms interruption of the main arc current. The control system regulates the bead area by controlling the pulse duration of the TIG process. Comparisons are made between the required and the actual front face bead areas in real time, the arc current being returned to the background level when the required area is reached. The front face area control system has been tested extensively on type 304 stainless steel, using plate thicknesses from 1.65 mm to 2.7 mm, and was found to perform well. The image of the weldbead does not have to be in the centre of the screen, as long as the whole bead appears within the field of view of the camera. This leads to simple operation with a short set-up procedure.