Feed forward control of welding process parameters through on-line ultrasonic thickness measurement

Abstract

Accurate control of welding parameters, such as arc power and wire speed, is critical for successful and appropriate weld joint penetration. The thickness of components being welded is a key parameter in defining optimum arc power for successful penetration, but is not always known beforehand or well controlled in manual and automated welding operations. This paper presents a novel feed-forward, sensor enabled, arc process control strategy based on ultrasonic thickness measurement. An ultrasonic wheel probe, deployed simultaneously alongside the welding torch, enables plate thickness measurement when coupled with a low-latency thickness measurement algorithm deployed on a real-time controller. An automated GTAW fusion control strategy, based on wheel probe measured plate thickness, provides direct input control of arc current, welding torch travel speed and filler wire feed rate. A parametric relationship between ultrasonically measured sample thickness and key arc welding parameters for welding S275 mild steel samples of thickness between 4.1 mm and 6.1 mm was established and verified. It is demonstrated that the system can measure and derive plate thickness while adapting arc power in real-time, with sufficiently low-latency, to allow consistent weld seam and uniform penetration on variable thickness steel samples, which under normal open-loop circumstances lead to sample burn-through and excessive penetration.