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Development and demonstration of an autonomous, mobile welding robot capable of fabricating large‐scale customised structures.

An autonomous welding robot has been developed under the EC Framework V Growth program. The system comprises a global vision system for part location and orientation, and a robot transport vehicle (RTV) which carries a 6‐axis robot, robot controller, welding equipment, and local sensors at the welding torch. The RTV path, robot arm motion and weld process programming are performed automatically using sensors and specially customised simulation software.

The technology developed within the project was demonstrated, in November 2004, to be capable of identifying and welding large scale customised structures as found in the earth moving equipment and bridge fabrication industries.

The project demonstrated that current sensor technology is capable of being applied successfully to autonomous robots, but further developments in sensor technology are required to improve accuracy and joint access.

The NOMAD concept of autonomous mobile robots provides an alternative solution to welding mass customised structures.

This project demonstrated, for the first time, the capability of autonomous robots to weld large scale customised structures.

The development of robotized welding is truly impressive and is today one of the major application areas for industrial robots. The first industrial robots were introduced in the early 1960s for material transfer and machine tending. Not long after that, robots were used for spot welding and in the early 1970s for arc welding as well. During the years, significant developments have taken place both concerning the robot equipment and the welding equipment to meet the different challenges within the application area. This paper describes the development and progress of robotization in welding over the years and also some projections and trends for the near future.

The world's most powerful electron‐beam welding facility was officially commissioned in September, providing 75 k\V of beam power in a vacuum chamber measuring 7 × 3.6 × 3.6m. Single pass welds in steel up to 200m thick may be produced at high speed and prototype fabrications may be welded in the large chamber using numerically controlled manipulating equipment.

In this report, accounts will be presented on the experience obtained from approximately 100 practical applications of industrial robots. The industrial robots used derive partly from the company's own production as well as from other domestic and foreign robot manufacturers.

Surface forming control of welding bead is the fundamental study in automated welding. Considering that the vision sensing system cannot extract the height information of weld pool in pulsed GTAW process, so this paper designed a set of automatic measurement and control technology to achieve real-time arc height control via audio sensing system. The paper aims to discuss these issues.

The experiment system is based on GTAW welding with acoustic sensor and signal conditioner. A combination denoising method was used to reduce the environmental noise and pulse interference noise. After extracting features of acoustic signal, the relationship between arc height and arc sound pressure was established by linear fitting. Then in order to improve the prediction accuracy of that model, the piecewise linear fitting method was proposed. Finally, arc height linear model of arc sound signal and arc height is divided into two parts and built in two different arc height conditions, which are arc height 3-4 and 4-5-6 mm.

The combination denoising method was proved to have great effect on reducing the environmental noise and pulse interference noise. The experimental results showed that the prediction accuracy of linear model was not stable in different arc height changing state, like 3-4 and 4-5-6 mm. The maximum error was 0.635588 mm. And the average error of linear model was about 0.580487 mm, and the arc sound signal was accurately enough to meet the requirement for real-time control of arc height in pulse GTAW.

This paper tries to make a foundation work to achieve controlling of depth of welding pool through arc sound signal, then the welding quality control. So a new idea of arc height control based on automatic measuring and processing system through arc sound signal was proposed. A new way to remove environmental noise and pulse interference noise was proposed. The results of this thesis had proved that arc sound signal was an effective features and precisely enough for online arc height monitoring during pulsed GTAW.

The purpose of this paper is to investigate the corrosion of the heat‐affected zone (HAZ) and weld zone of austenitic stainless steels that have been welded using two different processes. The corrosion behavior is evaluated in synthetic seawater using the electrochemical polarization technique.

Welded and unwelded UNS S30403 specimens were welded by flux core arc, and gas tungsten arc welding (GTAW) techniques. The test equipment consisted of an electrochemical three‐electrode cell using synthetic seawater as the corrosive medium. The scan rate was 10 mV/s and the potential range was −500‐500 mV vs saturated calomel electrode. The pH for the synthetic seawater was around seven. The electrochemical tests were performed after 1, 2, 3, and, 11 weeks. The metal surface was characterized by examination using an inverted microscope and scanning electron microscopy.

The polarization measurements of the flux core arc welding‐HAZ showed a high corrosion susceptibility, while GTAW‐HAZ presented good corrosion performance.

With the application and correct interpretation of this electrochemical technique, designers, welding engineers, and manufactures can access important information and take correct decisions regarding welding processes to meet corrosion resistance requirements.

The methodology and approach of interpreting the polarization plots used in this research can be applied to study other welding techniques and different welded metals in specific corrosive media, which will be of value to the welding industry.

Automatic arc‐welding machines have been used in manufacturing plant for a number of years now. They are special machines for a special purpose. But one of the main problems for automatic arc‐welding machines is presented by assembly element inaccuracies. These inaccuracies arise even when the parts are being stamped in the press. What is no problem for the manual welder, for he sees the discrepancies and is able to bridge the gap, may only be solved by automatic arc‐welding machines if powerful clamping tools are used. The same problem is also present in principle when programmable inddustrial robots are used for arc welding instead of conventional automatic machines. However, initial successes have been recorded in bridging assembly element inaccuracies with an automatic program shift and pendulum movements for the welding torch attached to the industrial robot. In recent times, these features have been supplemented by the welding power source being equipped with a parameter selection unit.

This paper addresses important technical problems related with methodological limitations of welding project methods currently adopted, mostly regarding numerical modelling procedure of welding processes. The progress in high nano‐technologies give rise to the same approaches to be applied in traditional mechanics and material science, really concerning welding processes using various methods and techniques. Recent investigations of welded joints have shown the benefits related to the employment of neutron techniques, to obtain substantial information advancing quality and durability that cannot be found by using other means. Small Angle Neutron Scattering (SANS) and Neutron Diffraction (ND), in particular, consent materials characterization at atomic and nanoscale level, offering to the existing technologies the essential contribution of precise structural methods. The basic theoretical aspects are described, and some SANS investigations of weldments are reported. An experimental programme has been recently projected to develop welding processes, with quality assurance improvement, safety enhancement, life‐time management and cost effectiveness of the considered joints.

This paper reviews the Weldex exhibition held at the NEC in Birmingham in November 2003. Highlights of the show included VirtualArc from ABB, which is able to predict weld conditions using physics of the arc, the hybrid MSG‐laser welding process from Cloos and a new spot weld‐specific Motoman robot. Several manufacturers displayed off‐the‐shelf “plug and weld” cells including Cloos, Fanuc and Autotech Robotics. Servo controlled guns were also featured by Motoman Robotics and Rexroth Bosch. The latter also promoted its ultrasonic weld monitoring systems that integrate with Rexroth's medium frequency welding systems for high quality assurance spot welding. Finally, a new laser seam tracker from Micro Epsilon is described.

The aim of this study was to develop a new generation of automatic systems based on cutting-edge design and practical welding physics to minimize downtime caused by defects and machine faults on the barges. Automatic welding has been used frequently on offshore pipeline projects.

An automated welding robot system for sub-sea pipeline installation was constructed. The system utilized the double-car double-torch welding, which is light-weight and compact, suited for offshore applications. Several state-of-the-art technologies were integrated into the control system design, including a heterogeneous network based on EtherCAT technology, network communications based on CANopen, motor synchronization, all-position welding, etc. In addition, the utilization of the CAN bus reduced the number of cable lines and increased the extensibility of the proposed welding robot system. An internal clamp with copper shoes assured a nice root weld and narrow bevel design and the welding efficiency was improved accordingly.

The trial was carried out to verify the rationality and effectiveness of the proposed automated system. The deposition rate of the backing welding could reach 17.78 kg/h; the average time for each welding was 340 s. This system was unique in that it features a dual-torch welding head that allowed for the deposition of one run with twice as much material as a single torch head. The experiment showed that the double-vehicle double-torch mode can greatly improve the welding efficiency of pipeline installation during the welding process.

The automated welding robot system will be applied to offshore pipeline projects.

This robot is the first submarine pipeline installation welding robot to use a heterogeneous network based on EtherCAT technology. Various aspects of the submarine pipeline installation welding robot’s design and performance were discussed, including mechanical body design, control system design and welding process specification.