Many companies are focusing both research and design efforts on laser welding and its subsequent applications for many reasons, starting with efficiency and the fact that it is able to guarantee high productivity with respect to cycle times. Compared to spot welding, laser welding – especially remote laser welding – offers added flexibility in terms of ease-of-use and throughput. The technology also eliminates process downtime and is among the fastest available on the market. Yet the true advantage of laser welding is its strength. A single welding point is an asymmetric junction between the joined plates which due to its very geometry does not have a preferred direction of resistance. A linear stretch of laser welding measuring 25mm in length with a width of 8 tenths of a millimetre, appears to be more resistant by around 30 percent, depending on the type of steel to be joined.

Laser welding also ensures quicker and more accurate processing than conventional spot welding. Remote laser welding, in particular, offers further advantages in terms of increased positioning speed and the reduction of criticalities of access between the robot head and tooling to achieve the joint. Whereas a conventional focusing head needs to be moved and repositioned to complete each welding stitch, Comau’s SmartLaser technology allows remote operation (>750 mm). In addition, the welding stitch can be quickly and easily modified simply by adjusting the working angle of the laser beam and its focal length. Remote laser welding also makes it possible to reduce the flange width of the joints by up to five millimetres and use profiles elements (hydroforming) with a significantly higher process speed (two laser stitches per second) than how it would be possible with spot welding.

For these reasons it can be argued that the laser represents a significant advantage for any type of production that requires high speeds. It is especially beneficial, if not critical, for the production of moving parts and all the areas of that must be welded together to create the geometry of the body during the framing phase. And while the cost of the technology is still elevated, due exclusively to the high cost of the apparatus that generates the beam, the performance it delivers in terms of increased productivity, higher overall quality and the virtual elimination of downtimes certainly compensates the initial capital investment.

The SmartLaser welding system integrates a remote laser focusing and repositioning module with a standard articulated robot to create a comprehensive solution that combines the precision and versatility of robotics with high-speed and extremely accurate laser technology. SmartLaser consists of a patented 3D Remote Laser System that is fully integrated with a Comau robot and based on the CO2 remote laser application know-how (AgiLaser). What’s more, the entire system is controlled by a single C5G Control Unit.

How SmartLaser works is as innovative as it is easy. The high-quality gain medium (beam source) is positioned near the welding cell, and the laser beam is transmitted by an optical fibre that is coupled to the robot at the axis 4. The fast handling of the mirrors, which intercept the laser beam and direct it onto the work piece, helps eliminate stresses to the fibre as well as issues related to the presence of external equipment. The solution also combines the reduction of mechanical stress with the added simplicity of off-line programming. In addition, SmartLaser delivers a high quality of dynamics across the entire workload, with acceleration of the linear motors of up to 8G. In addition, the repositioning speed of the Z axis is equal to 10 times that of a normal articulated robot.

When using laser welding on complex objects repositioning and control become important considerations, and in Body-in-White (BIW) operations there are essentially two possible approaches. You can move the piece that needs to be welded, as in the case of gears, but this is only possible if it can be moved on a single axis. The other option is to move the beam itself, or rather the focus of the beam which, in the case of SmartLaser, is integrated within the robot, which is how bodyshells are welded. This is because the shell cannot be rotated on a single axis and bodyshell welding requires that the beam to be repositioned for each different section. However, the act of physically moving the robot from one welding point to another can significantly affect the production process, giving rise to very low yields and very high costs. If one considers the speed of the laser in terms of how quickly it welds and the reduced thickness of the sheets to be joined, the beam source would only be used for approximately 15 to 20 percent of the working cycle. The remaining 80 to 85 percent of the time would be dedicated to moving from one point to another.

Remote laser welding solutions can increase productivity and subsequent profitability, especially for high-volume operations. Sticking with our bodyshell example, the framing phase is where the geometry of the body takes shape as the top, bottom and side parts are welded together. To proceed through the framing phase multiple locking tools are activated, which means you need to go through several steps from one end of the body to another in order to weld it together. The same is true in the completion phase; even if there are fewer locking systems and the “circumnavigation” times are shorter by around 35 percent.

Here is where SmartLaser enables auto manufacturers to reduce transfer times and increase “hot” phases – those in which the laser in active and is performing welding.  Remote laser welding, in the case of SmartLaser, means the ability to obtain a weld of six millimetres in diameter from over a metre away, with the added possibility of easily redirecting the beam. This means that there are markedly fewer movements of the system, which increases the possibility for the laser to be active, thereby increasing the hot phases and rendering the entire process more efficient. Thanks to the speed of the optical cavity mirrors that direct the laser beam at the different points to be welded, and the speed of the robot during its transfer movement, the SmartLaser beam remains in the welding position for the exact time necessary to weld and then quickly move to the next step.

Laser brazing, another laser-driven technology for BIW, is largely used for aesthetic joints due to its high seam quality, which enables the assembly of the outer parts without the need for revision operations. The increased use of laser brazing has created new opportunities for Comau’s laser-driven BIW solutions that several years ago were considered impossible. Current applications areas include roof joining and the assembly of the upper and lower panels of the tailgate/decklid, for example. The big advantage of roof laser brazing is the removal of the seals and side mouldings, in addition to the obvious improvement in overall aesthetics. For the tailgate, the ability to stamp the outer panels in two parts makes it possible to simplify operations in the stamping process. This combination of precision and quality inherent to laser brazing allows it to satisfy the stylistic requirements of each customer.

Although laser welding is a process commonly used with steel, the technology can also be applied to lightweight materials, such as aluminium parts. Comau’s Smart5 NJ110 Robot for aluminium welding for roof and deck lids, for example, can perform the welding of zero-gap joint in visible areas and welding in edge and lap joints. Considering that vehicle aluminium content is expected to approach 35 billion pounds, the automotive industry will become the most important global market for this material and the laser welding technology has an increasing part to play.

 The very first application for Comau’s remote laser welding solution was at the Cassino (Fr) plant for the production of doors for the Fiat Bravo, Lancia Delta and Alfa Romeo Giulietta. Today, Comau’s SmartLaser is being used for remote laser welding, roof laser welding and underbody laser welding. On a worldwide scale, it is deployed at Fiat of Pernambuco, Brazil, passing through the Melfi factory in Italy, as well as in central China to produce Jeep and Fiat, in Serbia for the production of the 500L and in the Tofas plant in Turkey for new Fiat models.