Welding robots: new trends and developments

Citation

Norberto Pires, J. (2005), "Welding robots: new trends and developments", Industrial Robot, Vol. 32 No. 4. https://doi.org/10.1108/ir.2005.04932daa.002

Welding robots: new trends and developments

Robotic welding is one of the most successful applications of industrial robot manipulators worldwide. In fact, a huge amount of products require welding operations in their assembly processes. The car industry is probably the most important example, with the resistance spot and MIG/MAG welding operations in the car body workshops of the assembly lines. Nevertheless, there are an increasing number of smaller businesses, client oriented, manufacturing small series or unique products designed for each client. These users require a good and highly automated welding process in a way to respond to client needs in time and with high quality. It is for these companies that the concepts of agile production apply the most, obviously supported by flexible manufacturing setups. Despite all this interest, industrial robotic welding has evolved slowly and is far from being a solved technological process, at least in a general way. The welding process is complex, difficult to parameterize and to effectively monitor and control. In fact, most of the welding techniques are not fully understood, namely the effects on the welding joints, and are used based on empirical models obtained by experience under specific conditions. The effects of the welding process on the welded surfaces are currently not fully known. Welding can in most cases (i.e. MIG/MAG welding) impose extremely high temperatures concentrated in small zones. Physically, that makes the material experience extremely high and localized thermal expansion and contraction cycles, which introduce changes in the materials that may affect its mechanical behaviour along with plastic deformation. Those changes must be well known in order to minimize the effects.

The majority of industrial welding applications benefit from the introduction of robot manipulators, since most of the deficiencies attributed to the human factor are removed with advantages when robots are introduced. Also, the welding process is very dangerous and demanding in precision and operator attention, requiring substantial physical efforts from operators, which makes it a good candidate for robots. Using robots for welding tasks is not straightforward and has been a subject of various R&D efforts. And that is so because the modern world produces a huge variety of products that use welding to assemble some of their parts. If the percentage of welding connections incorporated in the product is big enough, then some kind of automation should be used to perform the welding task. This should lead to cheaper products since productivity and quality can be increased, and production costs and manpower can be decreased. Nevertheless, when a robot is added to a welding setup the problems increase in number and in complexity. Robots are still difficult to use and program by regular operators, have limited remote facilities and programming environments, and are controlled using closed systems and limited software interfaces.

In this issue a selection of papers discuss some of these problems, describing at the same time new developments and current trends. The paper by Gunnar Bolmsjo et al. (pp. 341-45) presents a task oriented system that incorporates sensor interaction into the process of programming robot welding tasks. The paper explores the idea of dividing each task into generic sub-tasks that incorporate simulated runs and actual shop-floor runs constituting a powerful testbed for new sensors, strategies and control algorithms. The paper by Jeremy Smith et al. (pp. 334-40) shows that image processing systems are still useful for weld bed measurements and subsequent process control. This very interesting paper also discusses aspects related to system integration and, i.e. related to the interface of the presented system with legacy welding equipment.

The paper by Melton et al. (pp. 346-49) shows one of the developments of the NOMAD EU IP project financed by the fifth framework program. The presented robot system is based on a robot transport vehicle which carries a six-axis robot based welding system. The system is presented along with some application examples.

Finally, the paper by Pires et al. (pp. 314-17) discusses the advantages of using CAD software packages to program robotized welding systems, showing one simple example on how that can be achieved. CAD software is used commonly within companies for product development, which makes the presented approach interesting for actual robot programming.

This issue demonstrates that welding is a very challenging activity still requiring research input and application oriented developments.

J. Norberto PiresBased at the University of Coimbra, Coimbra, Portugal