Although laser welding processes are increasingly being employed, Steed Webzell discovers that resistance spot welding is still experiencing high levels of development
Laser and resistance spot welding are two processes that compete for the same automotive applications – choosing between them requires careful analysis. Rather than go over the welltrodden advantages and disadvantages of each process, recent sales activities and technology developments arguably provide a clearer picture of current industry thinking.
In China, the sector’s most active car market, Soutec AG (now part of the Andritz Group) reports that it is about to supply laser welding systems for Chinese automotive and steel producers – both for the production of tailored blanks. Soutec Soulas systems are used for linear welding seams and each has an annual capacity of 1.2 million tailored blanks.
Beijing-based BAIC Motor, part of the Beijing Automotive Group, will use its new laser welding system to help manufacture the company’s C70G, C50E and C60F models, while PCMI Metal Product of Chongqing is ordering its first laser welding system with the intention of entering the market for tailored blanks. Installation and commissioning for both systems is scheduled for the third quarter of 2013.
Soutec says that the tailored blanks produced using its laser welding systems contribute towards making cars safer and up to 100kg lighter, thus reducing fuel consumption and CO2 emissions. This point is echoed by EMAG, a specialist in manufacturing systems for metal components.
“For every 100kg deducted in vehicle weight, fuel consumption is reduced by up to 0.3 litres per 100km,” says Dr Andreas Mootz, managing director of EMAG Automation. “The level of innovation behind these efforts is exemplified by passenger car transmissions, where gear wheels and related components are manufactured by the millions. Here, high-tech solutions such as laser welding can realise spectacular results.”
Engineers have created a simple yet highly effective weld joint that is used by German automakers to replace the previous threaded connection between differential components. “This reduces the amount of material required, which lowers the unit price. The weight of the differential housing is reduced by approximately 1.2kg – little short of impressive in the automotive world,” claims Mootz.
According to EMAG, its automated ELC equipment is used widely in the German automotive sector to manufacture such transmissions. The machine starts by loading components before pressing them together and welding the gap. Additional processes may also be carried out depending on the component. Each gear wheel is finished in just 12 seconds and all differential components are fully welded in less than 40 seconds.
Scanning the benefits
It seems that auto manufacturers looking to implement much-publicised remote laser welding processes could benefit from the merger of two technology specialists. SCANLAB, a manufacturer of scanning systems used in laser material processing, has acquired Blackbird Robotersysteme, a producer of control solutions for robotic laser welding equipment.
According to SCANLAB, the two companies have been working together since 2009 and offer what it calls “the most capable 3D scanning solution currently available for remote laser welding” – the intelliWeld high power scan heads controlled by the RobotsyncUnit.
The firms have apparently been working with BMW to develop a novel scanning technology for remote laser welding stations that are currently being installed at the auto giant’s MINI pressings facility in Swindon, UK. The new approach features a mirror that pivots within the scanning head, meaning that relatively complex welding processes for hang-on parts, such as doors, can be completed in a single, rapid sweep rather than requiring several more intricate steps that would slow the production line.
But what of resistance spot welding? Well, tier supplier Georg Fischer Automotive is exploiting an alternative version of this mature joining technology. Unlike conventional spot welding, its the company’s DeltaSpot overcomes the obstacles that have so far prevented the high productivity joining of aluminium.
Experts from Georg Fischer have been working with welding system partner, Fronius, to develop a solution for the door frame of the new Porsche Panamera. According to Wolfgang Hintsteiner, the engineer in charge of this project at Georg Fischer, the installation has proven to be both reliable and cost-effective.
GM’s aluminium breakthrough
In Detroit, General Motors’ R&D team says it has invented an industry-first aluminium welding technology expected to enable more use of the lightweight metal on future vehicles. The new resistance spot welding process uses a patented multi-ring domed electrode that does what smooth electrodes are unreliable at doing – welding aluminium to aluminium. By using this process, GM expects to eliminate around 0.9kg of rivets from aluminium body parts such as hoods, liftgates and doors.
The OEM already uses the patented method on the hood of the Cadillac CTS-V and the liftgate of hybrid versions of the Chevrolet Tahoe and GMC Yukon, and plans to use the technology more extensively throughout 2013.
“The ability to weld aluminium body structures and closures in such a robust fashion will give GM a unique manufacturing advantage,” says Jon Lauckner, GM’s chief technology officer and vice-president of Global R&D. “This new technology is an important step forward that will grow in importance as we increase the use of aluminium in our cars, trucks and crossovers over the next several years.”
“No other automaker is spot welding aluminium body structures to the extent we are planning, and this technology will allow us to do so at low cost,” adds Blair Carlson, GM’s manufacturing systems research lab group manager.
To put this capability in perpspective, according to Ducker Worldwide, a Michigan-based market research firm, aluminium use in vehicles is expected to double by 2025.