Ten years since Rofin-Baasel Lasertech invented the sweet spot resonator, this patented now extends to a new third generation system and into the 200 W average power range.
Excess heat inside a YAG rod, which is water cooled on the outside (a standard feature of Nd:YAG lasers), creates a "thermal lens" which is influenced by the average power level. This induced thermal lens changes the divergence of the laser beam which can lead to a variation in spot size and penetration depth during the course of a seam weld. Rofin's patented sweet spot resonator ensures that the characteristics of the first laser pulse are the same as the last thus eliminating any variation in weld penetration depth and creating a more even weld profile.
The pulse-to-pulse stability and large depth of field, both key features of the sweet spot technology, enable excellent results to be obtained in manual welding applications. The extraordinary beam quality produced by this technology means that the weld quality is not wholly dependent upon exact positioning of the part within the focal point of the beam - a decisive advantage for hand welding applications.
Another area where the sweet spot resonator technology has proved to be especially effective is in the field of processing highly reflective materials such as copper, gold and silver. These materials are commonly used in jewellery production and the dental industry, where laser welding is fast becoming the preferred method of joining. In addition, Rofin's sweet spot resonator technology allows processing of the finest and most delicate components with weld spot diameters smaller than 100 μm using Rofin's MicroWeldTM function.
New application areas
Seam welding applications on sheet metal is one area where the advantages of the sweet spot resonator can be clearly seen. The consistency and predictability of the process, achieved from the excellent beam quality, vastly reduces the setup and development times normally associated with welding on thin metal components. The high pulse-to-pulse stability produced also ensures process reliability. This is particularly important on components such as medical devices and implants where fine tolerances and high quality must be achieved on each and every part.
This latest extension of the sweet spot resonator technology into the 200 W power range means that it can now be applied to many new areas. Applications such as aluminium welding or sealed membrane welding of pressure sensors will now benefit from the sweet spot resonator technology, variable pulse shaping and extremely precise parameter adjustment. In addition, the availability of 200 W of power will be highly beneficial in high volume production applications.
The efficiency of this technology enables 200 W of laser power to be produced using one single, new generation, flashlamp which also offers a considerably longer life time. This is also highly beneficial for the ongoing maintenance of the system as only one lamp has to be replaced, thus reducing operating costs in comparison to the more commonly used two lamp resonators in this class of laser.