Joined-up thinking

A laser-based technique could overtake resistance technology as a faster welding method for automotive and other applications.

Change in automotive industry production methods happens slowly. With hundreds of millions of pounds invested in incumbent manufacturing techniques, it’s easy to see why.

But with the world’s car manufacturers increasingly keen to reduce the weight of their vehicles and to improve the efficiency of their manufacturing processes, a number of advanced manufacturing techniques are receiving increasing amounts of attention.

One technology with particular promise is remote laser welding (RLW), an emerging joining technique that many believe has potentially huge advantages over the spot welding technology that is widely used in the automotive industry.

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Laser welding could one day be used in a range of sectors

Working with €4;4m (£3.3m) of EU funding, the UK-based Warwick Manufacturing Group (WMG) has joined forces with industry partners, including tier-one automotive supplier Stadco along with Jaguar Land Rover, to help usher this innovative welding technique into the manufacturing mainstream.

Prof Darek Ceglarek, who is heading up WMG’s RLW Navigator (Remote Laser Welding System Navigator for Eco Resilient Automotive Factories) project, explained the differences between resistance spot welding and its potential rival.

Resistance spot welding – which joins parts using the heat generated by resistance to the flow of electric current – is a contact technology. This means that access is required to both sides of the part to make a joint.

By contrast, RLW is a non-contact technology and only requires access to one side of the part – a single high-power laser beam is used to create the joint. By having laser optics embedded into the robot, and a scanning mirror head as the end effector, RLW can easily create joints in different locations of the product through simple robot repositioning and laser beam redirection from a remote distance. This means that, as long as there is a ’line of sight’ between the scanning mirror and the joint location on the assembly, creating a laser weld may be feasible.

Using this approach, RLW is able to create a joint in a fraction of a second, and Ceglarek estimates that the process is as much as five times faster than spot welding.

“As RLW is faster, one robot is available to carry out more work- reducing the amount of floor space required”

But the advantages don’t end there. Because it’s faster, one robot is able to carry out more work, and this means that floor space could be reduced by as much as 50 per cent.

The requirement for fewer robots could also have major implications for maintenance costs and energy usage. Ceglarek claimed that, overall, RLW could reduce assembly costs by 10 per cent.

The technology also has some less obvious but equally compelling design implications. A vehicle’s design typically takes into account the manufacturing techniques that will be used to produce it, and most cars contain a high number of flanges on the edges of parts joined using spot welding. With RLW, these flanges – which contribute around 200kg to a car’s weight – could potentially become redundant: a very attractive advantage for an increasingly weight-conscious industry.

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Remote laser welding could help cut the weight of cars

So far, RLW has been limited to fairly niche applications of low-production-run components. This is largely because engineers have struggled to find a way of controlling the process with the degree of repeatability and accuracy required for high-volume production. Indeed, according to Ceglarek, most existing applications of RLW have relied heavily on trial and error to get the process right.

The big challenge, he said, is that effective laser welding requires the extremely close control of the gap between the parts to be joined – and the discrepancies between the tolerance of the parts to be joined can make it extremely difficult to maintain the optimum gap between the components.

The aim of the WMG project is to develop a simulation tool that will replace guesswork with precise mathematical modelling that will quickly deliver the efficiencies manufacturers want from this process. Ceglarek explained that the aim is to develop a system able to precisely model the process, configure the production systems and optimise the control of the welding.

There’s clearly a long way to go in the development of what Ceglarek describes as a high-risk project. But with Jaguar Land Rover reportedly keen to see the technology developed as quickly as possible, he hopes that it could be helping to reduce assembly times within the next few years.

In the longer term, with many of the fundamental challenges cracked, it is hoped that the technology could be deployed across a range of sectors.

in depth good fit

Laser-based technology is also playing a role in addressing welding issues in the oil and gas industry – where high-precision pipeline welding is vital to ensure smooth runningIn oil and gas pipeline projects, the welding of fatigue-sensitive pipes to tight specifications is absolutely critical.

In order to prevent bottlenecks during the welding process and to minimise project delays and risks, oil industry owners, pipelay contractors and welders need to capture, record and analyse pipe end geometry quickly and accurately. This measurement data, if used in the correct way, can then help to ensure that pipes delivered into the bead stall will fit together within the specification requirements for welding.

Typically, end dimensioning and fit-up involves two main steps: measuring and fit-up. The measuring stage involves the actual collection of pipe measurement data. Here, automatic, laser-based measurement tools can be used to measure the geometrical features of pipe ends, normally performed on shore, although this process sometimes needs to occur on a cargo barge.

Laser-based measurement tools can be used to measure the internal diameter (ID) and wall thickness (WT) of pipe ends in rapid time. Typically, several thousand IDs of a pipe can be measured in less than half a minute, enabling hundreds of pipe ends to be measured in a single shift. This means less time on site, minimising project delays and costs for the pipelay contractor.

Data from laser-based measurement tools can be made available to pipe optimisation software, which is able to predict and control the fit-up, before the pipes are brought into the bead stall for welding.

Each pipe end is measured, identified and entered into the software. The software analyses the fit-up of pipes and allows the operator to mark the best rotational position on each pipe end. In the bead stall, these marks are aligned in order to immediately achieve the best rotational position so that misalignment is minimised.

A number of pipelay contractors are benefiting from working closely with experienced, independent measurement specialists such as OMS – helping them to avoid a range of potential issues such as wall thickness problems and poor fit-up on board ’J-lay’ vessels.

production essentials

The key facts to take away from this article

  • Many believe that remote laser welding is better than spot welding
  • The laser-based method is able to create a joint in a fraction of a second
  • The technology could reduce assembly costs by up to 10 per cent
  • WMG aims to develop a mathematical simulation tool to improve efficiency