The power output of commercially available continuous wave (CW) Nd:YAG lasers has increased substantially over the last few years. Models which can deliver 4 kW to the workpiece are now available. At this power level, the Nd:YAG laser can effectively compete with the CO2 laser in many laser welding applications. The easier, fibre optic based, beam delivery of the high power Nd:YAG laser makes a number of applications possible which were considered impractical using CO2 laser technology.
This paper will first describe the general characteristics of an Nd:YAG laser system as configured for welding, and contrast these features with a typical CO2 laser welding system. Points of discussion include: laser power, beam delivery options, focus spot characteristics including the capabilities of twin spot beam delivery with an Nd:YAG laser, and the interaction of the laser beam with the metal surface, including a brief description of the laser generated plasma. Some specific configurations for an Nd:YAG laser-based weld cell will then be described.
In the second section, a number of applications for Nd:YAG laser welding will be described, and sample parts and weld characteristics will be shown. These applications include: welding of tailored blanks for body stampings using 1D and 2D weld geometries, welding of reinforcing patches onto blanks for shock towers, laser welding of hemmed door and hood joints, laser welding of tailored tubes for hydroforming, laser welding of aluminum panels, and laser welding for auto body assembly.
The Nd:YAG laser is not expected to replace the CO2 laser completely, but there are a number of applications which are better suited to laser welding with an Nd:YAG than a CO2 laser. The ability to deliver the laser power to the workpiece through a flexible fibre also opens new laser welding applications, and creates more competition for traditional joining techniques.