A sensor enabled robotic strategy for automated defect-free multi-pass high-integrity welding

Loukas, Charalampos and Warner, Veronica and Jones, Richard and MacLeod, Charles N. and Vasilev, Momchil and Mohseni, Ehsan and Dobie, Gordon and Sibson, Jim and Pierce, Stephen G. and Gachagan, Anthony (2022) A sensor enabled robotic strategy for automated defect-free multi-pass high-integrity welding. Materials and Design, 224. 111424. ISSN 0261-3069 (https://doi.org/10.1016/j.matdes.2022.111424)

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High-integrity welds found in safety–critical industries require flaw-free joints, but automation is challenging due to low-volume, often-unique nature of the work, alongside high-uncertainty part-localisation. As such, robotic welding still requires tedious manually taught paths or offline approaches based on nominal Computer-Aided-Design (CAD). Optical and laser sensors are commonly deployed to provide online adjustment of pre-defined paths within controlled environments. This paper presents a sensor-driven approach for defect-free welding, based on the as-built joint geometry alongside the requirement for no-accurate part localisation or CAD knowledge. The approach a) autonomously localises the specimen in the scene without CAD requirement, b) adapts and generates accurate welding paths unique to the as-built workpiece and c) generates robot kinematics based on an external-control strategy. The proposed approach is validated through experiments of unconstrained placed joints, where the increased accuracy of the generated welding paths, with no common seam tracking, is validated with an average error of 0.12 mm, 0.4°. Coupling with a multi-pass welding framework, the deployment of fully automated robotic arc welding takes place for different configurations. Non-Destructive-Testing (NDT) in the form of Ultrasound-Testing (UT) inspection validates the repeatable and flaw-free nature of the sensory-driven approach, exploiting direct benefits in quality alongside reduced re-work.