Increasingly connected, more precise laser processes are helping to crack the tough nuts in industrial manufacturing. From joining different raw materials, to integrating sensors into components, to specifically functionalizing surfaces.
Lightweight construction companies know how difficult it is to combine steel and aluminum robustly. This is also something shipbuilders are struggling with in order to reduce the weight of ships and, with it, their energy demand. Since hulls are still made of steel for stability rea-sons, but the superstructures are increasingly based on aluminum, permanent connections are required that will last the life of the ship. For this purpose the Laser Zentrum Hannover (LZH), together with Coherent, Precitec, B.I.G. and other industrial partners, is developing a new laser welding process. At its heart is a laser processing head that emits crossing laser beams. During the process, an X-shaped anchor digs millimeters deep into the steel-aluminum composite beneath the overlap weld seam on the surface. The process is precisely monitored with the help of spectral analyses of the process emissions and short-coherence interferometry. This makes it possible to precisely control how deep the bonded, pass-fitting undercut penetrates the material, even if there are any variances in the material.
This kind of precise metrological monitoring of laser processes, with instruments provided by photonics, is what sets modern laser-based manufacturing processes apart. This makes the vision of a world of fully networked, 100% quality-monitored, data-controlled Industry 4.0 pro-cesses into a reality. Another example of this comes from SCANLAB in the form of a new laser micro drill head that is connected to an optical measuring system from stoba Custom-ized Machinery. Its measurement data is continuously evaluated in order to readjust the pro-cess on-the-fly, even with minimal deviations from the target. Because errors can no longer creep in, this significantly reduces rejects and the effort needed for control, which makes the five-axis micro-machining system ideal for 24/7 industrial use. Because an automated fin-ished part control including documentation is implemented at the same time, the solution comes astonishingly close to the vision of almost independent Smart Factory processes. Above all this is because the femtosecond laser used in connection with the measuring sys-tem brings the necessary flexibility for smooth changeover when changing jobs.
In addition to seamless metrological monitoring, there are new possibilities for beam shaping, such as Coherent’s Adjustable Ring Mode (ARM) technology. Here, a fiber laser beams a central point that is surrounded by another laser light ring. The power and modulation of the center spot and ring spot can be controlled independently of each other and they can be switched on and off independently. This makes it possible to process even very difficult metals such as copper with high precision and without spatter using inexpensive infrared (IR) lasers. For background, because copper absorbs red light poorly, green or blue solid-state lasers are often used. The ARM process addresses this problem because the ring beam preheats the metal, which optimizes its absorption behavior and benefits the subsequent, precise machining process with the center spot. The ability to flexibly shape the beam makes IR fiber lasers a viable technological alternative – an alternative that the likes of the automotive industry are urgently looking for. That’s because, with the transformation to electric mobility, copper is becoming the standard material for motors, batteries, converters and their cabling. The industry needs solutions that can cope with large-scale production processes and create material connections that meet the highest quality standards despite the usual process speeds of a few decimeters per second.
The various current projects that the Fraunhofer Institute for Laser Technology (ILT) Aachen and its partners are advancing demonstrate what potential for productivity is yet to be uncovered in laser processes—and that it can be leveraged with ingenuity. This includes high-rate laser ablation using an ultra-short pulse (USP) laser. In principle, this is predestined to prepare the base for high-quality material connections—for example when contacting the electrodes of lithium-ion batteries. The µm-thin metal foils are coated with active material in a complex process, with gaps previously being left at regular intervals for the contact points. It would be easier to apply the active pastes consistently and then to expose the contacting zones. USP ablation would be suitable because the cold, high-precision process does not damage the wafer-thin metal foil any further. But so far the ablation process has been too slow for that. This isn’t the case with new multi-kilowatt lasers, which achieve residue-free ablation rates of up to 1,760 mm³ per minute—making them ready for industrial use.
The same applies to the exact opposite process: Extreme high speed laser application (EHLA), also developed at the ILT, in which metal powder is melted by laser in an air stream—and applied to metal surfaces. For example, highly stressed component areas can be immunized against corrosion and wear through the targeted application of at least 25-micrometer-thin layers—at speeds of up to 500 meters per minute. Here, metallurgically incompatible metals such as aluminum and titanium also form permanent bonds that are insensitive to the effects of heat. The ILT researchers are currently working with partners from the aviation and mechanical engineering sectors to make the EHLA process usable for Additive Manufacturing with high build-up rates.
In additive metal printing processes, ILT researchers also integrate sensors and actuators into metal components. The smart components are installed in door mechanisms, dampers and wheel bearings on Deutsche Bahn trains, where they collect temperature and acceleration data using AI-supported condition monitoring.
And there is another, highly exciting technological approach from the ILT and EdgeWave, which could result in a productivity boost for laser processes. It is a multi-beam system, in which a laser beam is initially divided into 16 and now even 64 partial beams. These can be controlled in parallel and individually, and used to micro-structure functional surfaces. The basis is a 500 watt USP laser from EdgeWave, whose beam is distributed by special optics to dozens of partial beams, each with the same beam parameters that can be individually modulated. All beams can be switched on and off separately. According to the ILT, the new multi-beam system is suitable for battery and hydrogen technology, but also for the large-scale structuring of aircraft wings and wind turbine blades to reduce their aerodynamic drag.
TRUMPF recently reported a productivity boost in laser production that has already been implemented. Specifically, this refers to a fully automated system for cutting sheet metal. Using laser blanking, they process up to 25 tons of rolled sheet metal without human intervention – precisely and with minimal waste. This makes the system a highly flexible alternative to the mechanical sheet metal working presses previously used, which require a new tool for every new job and every change. With the laser, such changes work without the time-consuming and costly production of a new tool. And because the cutouts can be optimally nested, TRUMPF claims that the material requirements are reduced by up to 30 percent. Laser blanking is becoming a fast, inexpensive alternative for large-scale production processes in which mechanical presses have previously come in first. Here, too, the networked, digitally controlled laser process is paving another part of the way to Industry 4.0.