Online programming system for robotic fillet welding in Industry 4.0

Purpose Fillet welding is one of the most widespread types of welding in the industry, which is still carried out manually or automated by contact. This paper aims to describe an online programming system for noncontact fillet welding robots with “U”- and “L”-shaped structures, which responds to the needs of the Fourth Industrial Revolution. Design/methodology/approach In this paper, the authors propose an online robot programming methodology that eliminates unnecessary steps traditionally performed in robotic welding, so that the operator only performs three steps to complete the welding task. First, choose the piece to weld. Then, enter the welding parameters. Finally, it sends the automatically generated program to the robot. Findings The system finally managed to perform the fillet welding task with the proposed method in a more efficient preparation time than the compared methods. For this, a reduced number of components was used compared to other systems: a structured light 3 D camera, two computers and a concentrator, in addition to the six-axis industrial robotic arm. The operating complexity of the system has been reduced as much as possible. Practical implications To the best of the authors’ knowledge, there is no scientific or commercial evidence of an online robot programming system capable of performing a fillet welding process, simplifying the process so that it is completely transparent for the operator and framed in the Industry 4.0 paradigm. Its commercial potential lies mainly in its simple and low-cost implementation in a flexible system capable of adapting to any industrial fillet welding job and to any support that can accommodate it. Originality/value In this study, a robotic robust system is achieved, aligned to Industry 4.0, with a friendly, intuitive and simple interface for an operator who does not need to have knowledge of industrial robotics, allowing him to perform a fillet welding saving time and increasing productivity.

A Study on Cross-Shaped Structure of Invar Material Using Cold Wire Laser Fillet Welding (PART I: Feasibility Study for Weldability)

With the need for eco-friendly energy increasing rapidly due to global environmental issues, there is a rapidly increasing demand for liquefied natural gas (LNG). LNG is liquefied at minus 163 degrees Celsius, and its volume decreases to 1/600, giving it a relatively higher storage and transport efficiency than gaseous natural gas (NG). The material for the tanks that store cryogenic LNG must be a material with high impact toughness at cryogenic temperatures. Invar, which contains 36% nickel and has a very low coefficient of thermal expansion, is used for the membranes and corner structures of LNG cargo holds. The cross-shaped Invar structure used in an LNG cargo hold is manufactured through manual tungsten inert gas (TIG) fillet welding, which causes welding distortion and weldability problems. This study is a feasibility study that aims to reduce welding distortion, increase weldability with welding speed, and reduce the steps in an existing process by half by replacing the existing manufacturing method with automatic fiber laser fillet welding. Laser welding using fiber laser parameters are controlled for 1.5 and 3.0 mm thick Invar materials and weldability is secured through cross-section observation. Then, the optimal welding conditions with top and back beads secured are derived through a trial and error method.

Accurate FE Computation for Out-of-plane Welding Distortion Prediction of Fillet Welding with Considering Self-Constraint

Inherent deformation as key parameter plays an essential role in elastic finite element (FE) analysis for welding distortion prediction. In this study, the self-constraints supported by surrounding base material and lateral stiffener were presented, where their influences on magnitudes of inherent deformation components were qualitatively examined. In detail, self-constraint supported by the surrounding base material will distinguish the inherent deformation as an individual physical representation; and self-constraint supported by the lateral stiffener will significantly influence the bending component and final deformed mode. Taking into account fillet welding and orthogonal stiffened welded structure as the application, experiments were conducted for out-of-plane welding distortion measurement. Transient nonlinear thermal elastic-plastic FE analysis of fillet welding was carried out to evaluate inherent deformation after validation with the measured data; then, elastic FE analysis with inherent deformation was carried out to accurately predict the out-of-plane welding distortion and welding buckling behavior in fabrication of an orthogonal stiffened welded structure which is a part of typical ship panel, and there is a good agreement between the predicted and measured welding distortion.