Laser zoom processing head

A new "beam tool" developed by LIMO as part of a research project brings to mind the famous marketing slogan "There's always a clever head behind it." from the Frankfurter Allgemeine Zeitung, one of Germany's major daily newspapers. The special feature of this new compact laser head is its zoom function, which delivers a processing flexibility capable of handling an incredibly wide range of surface types.

The head measures 148 mm long with a diameter of 50 mm and is enclosed in an aluminum housing. As part of the ALPS project, this laser zoom processing head was developed at the Dortmund-based LIMO Lissotschenko Mikrooptik GmbH as a new beam shaping module for surface processing. Though the prototype is no more than half the size of the typical baton used by relay runners, it converts a continuous output of 1.0 kW (maximum short-time output: 2.5 kW) from glass fiber to a line focus – despite its miniature dimensions. "This is an extremely compact processing head which stands apart mainly thanks to its zoom adjustment feature," notes Dr. Thomas Mitra, Head of the Micro-optics Development Department. "The new tool can be used to make specific modifications to the line length during processing. This means that the laser beam can be set to trace contours or adapted to fit individual workpieces." The ability to quickly and easily adjust the zoom during processing decreases the amount of setup time required. This results in greater process flexibility and therefore also enables economical laser processing of workpieces in small batch sizes. 

Mitra goes into greater detail for laser experts: "The extremely compact size was made possible by a new optical concept in which two special micro-optics are used to directly handle homogenization and length adjustment. Conventional setups first homogenize beams with micro-optics and then typically require three additional optics to adjust the line length along one axis."

Initially developed for the production of solar cells (wavelength of 808 nm to 1064 nm), this concept could also be used in laser plastic welding to adapt the line width (0.2 mm to 0.6 mm) or length (4 mm to 12 mm) to individual workpieces – without switching the laser or replacing the processing head. According to Dr. Mitra, the laser head is particularly beneficial where lasers are used to weld plastics, since it allows even those parts to be welded which have varying widths along the weld seam. Because of its compact and lightweight design, the new beam tool can also be easily mounted on a robot arm or translation stage.

Using this concept as a starting point, LIMO is currently working to develop additional beam shaping modules for outputs of 6 kW and 10 kW. Thanks to a motorized zoom adjustment feature, these modules will also be suitable for automated processes and capable of handling larger, freely variable profiles (incl. adjustability on two axes). In addition to plastic welding, this compact technology can also be used in metal hardening and roll cladding.