FUEL CELL WELDING
A SPARK OF HOPE FOR THE FUTURE ENERGY GENERATION
How does a fuel cell work?
In a fuel cell, a continuously supplied fuel, for example hydrogen, reacts with an oxidizing agent such as oxygen from the air. Each individual cell consists of two plates, each with a gas distribution structure, separated by a membrane. In a polymer electrolyte fuel cell (PEM), the hydrogen is separated into H+-ions and electrodes. The H+-ions migrate through the membrane and react with the oxygen in the air to form water. The electrons flow through an external contact and deliver the desired electrical current. The end products of this chemical reaction are water, electricity, and heat. The electrochemical reaction in the fuel cell is also known as "cold combustion" and is
particularly efficient, clean and climate friendly.
Bipolar plates consist of a tightly welded metal anode and metal cathode (white in the picture) with gas distribution structures. Together with the membrane (MEA), they are the core components in fuel cells, which are layered in tightly compressed stacks and form the core of a fuel cell system. A stack can contain several hundred bipolar plates. As an integrated component, the plates carry out the following tasks: electrical connection of the cells, gas distribution across the surface of the plate, gas separation between adjacent cells, outward sealing, and cooling.
A great partnership: Fuel cell and laser technology
The use of modern laser deflection units in fuel cell technology makes sense not only because of its speed, accuracy, and effectiveness in industrial production, it also brings with it a major competitive advantage. Lasers cut and weld the bipolar plates with extreme precision without contact, force, or wear. Laser deflection units act as true drivers of innovation in the manufacturing process because they help to bring fuel cells into series production.
LASER APPLICATIONS IN FUEL CELL MANUFACTURE: CUTTING, CLEANING, WELDING
In detail, three areas are particularly relevant for fuel cell manufacture: cutting, cleaning and welding. The process of laser cutting gives the formed metallic half-plates of a bipolar plate their final contour. This includes an external cut, but also complex contours within the plate, for example, the openings for the gases. The laser with its very small spot diameters enables burr-free trimming of even the most difficult geometries at material thicknesses of up to 50 µm.
The welding process represents an important production step in bipolar plate manufacture, in which very thin stamped metal foils with delicate contours must be welded gas-tight (see graphic above). Compared to other methods, this can be realized much more efficiently and economically with a laser deflection unit. So-called single-mode lasers with corresponding beam quality can perform a heat conduction process or a deep welding process together with deflection units to produce the desired narrow weld bead. Alternatively, the fine laser beam can be shaped into a spiral shape with dynamic and fast deflection units or, with the aid of the software and control electronics, into any lissajous figure to achieve the desired welding result.
A tight welding of the bipolar plates ensures that the gases cannot mix. Since one single defect in a stack of hundreds of plates would make the entire fuel cell unusable.
BOTTOM LINE: Using deflection units in conjunction with laser technology eliminates the need for prefabricated tools such as cutting blades and stamps, which wear out very quickly and slow down productivity. In addition, these tools are not particularly versatile, as is the case for lasers and deflection units with control cards and software.
Fuel cell manufacturers benefit from consistently good quality, more productivity in terms of higher quantities with extremely low maintenance times, and savings in personnel costs and waste; all the time maintaining maximum process stability. The biggest plus, however, is flexibility as the software can be used to adapt the laser components to literally ALL applications.
Unique on the laser market
The AXIALSCAN FIBER-30 pre-focusing deflection laser system for pre-settable process field sizes between 250 x 250 mm² and 850 x 850 mm² is to date the only one of its kind on the market and also very well suited for producing fuel cells. An optional monitoring module is also available. This offers camera monitoring with autofocusing, as well as a second channel for adapting welding monitoring systems. The automatic focus tracking of the camera, in particular, represents a unique selling point of the product in the market. Welding is supported by the software functionalities of the latest RAYGUIDE software. It includes welding ramp functions that ensure the material to be processed is heated, helping to avoid fracture, and provides different lissajous figures for a range of laser beam modulations.
Image processing software solutions for production equipment and position detection using camera technology enable "just in time" tracking of the manufacturing steps. This not only helps to immediately detect if a workpiece is incorrectly positioned, but also to correct it immediately.