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Gearwheels Get Upgrade with Laser Welding

Article by EMAG LLC

Dr. Andreas Mootz

Dr. Andreas Mootz is managing director of EMAG Automation GmbH, Heubach, and responsible for the development of the production laser welding technology (all photos courtesy of EMAG).

From the dual-clutch transmission to the classic differential: modern transmission technology is a pivotal research sector in the automotive industry. With new materials and altered geometries, designers optimize the functionality of the different gearwheels. Furthermore, these wheels are required in ever larger quantities, owing to the fact that the number of speed-gears in many passenger cars is on the increase. The innovations that promote the effectiveness of the production processes being applied include, for example, laser welding. With their ELC series of machines, EMAG has developed integrated solutions for the application of processes with high output rates.

A first glance at a typical transmission component makes it plain where the challenges lie: even a small wheel with integrated synchronous gearing represents a relatively complex design. To manufacture it efficiently and at the highest precision calls for the two different parts to be produced separately and subsequently joined in a joining+welding process.

"It is at this point in modern transmission manufacture that laser welding comes into its own," explains Dr. Andreas Mootz, managing director of EMAG Automation. "The process allows you to concentrate a carefully dosed amount of the energy emitted by the laser beam on the welding point, minimizing possible warping, while still achieving high welding speeds."

Machining area of the ELC 160 Laser Welding Machine

Machining area of the ELC 160 Laser Welding Machine for the welding of gearwheels. On up to three stations, the wheel assembly is pre-heated, joined and laser welded.

Furthermore, the welding process from EMAG uses solid-state lasers offering more energy efficiency. Whereas a classic carbon dioxide laser will achieve an efficiency factor of just about eight percent, the EMAG specialists can rely on an efficiency factor of approximately 20 percent with their technology. In other words, the power used to achieve the same optical performance is noticeably less, with energy costs in the production department massively reduced.

Similarly effective within the total process is the integration of different production sequences on the ELC system. For starters, the work spindle uses the pick-up principle to load itself. The components involved are then clamped and pressed together in the joining press. The clamping technology used ensures the highly accurate positioning of the components, providing suitable conditions for the welding process. The design of the stationary optic ensures great operating safety and optimal stability of both machine and welding process. Depending on the workpiece material, the components can be induction-preheated prior to the welding process and brushed after it - and whatever is required, the process is completed in a single setup. The complete joining+welding process for a gearwheel takes just 12 seconds. This ensures that the components for a differential are thus finish-welded within no more than 40 seconds.

Laser-welded gearwheel

Laser-welded gearwheel.

The differential housing, as an example, clearly shows the possibilities the laser welding technology opens up in the general development of vehicle production. For some time now, automotive companies have been replacing the screw-type connection between differential housing and crown gear with a welded seam. The result: the cost of materials reduces and the weight of the assembly falls by approximately 1.2 kg or about 2.65 lbs. "When looking at the advances made in lightweight construction in the automotive industry, this kind of savings means the world," explains Mootz.

EMAG has sold more than 50 ELC systems in the last decade. "It is of decisive importance that we have at our disposal a large reservoir of know-how in the manufacture of these components. We understand the entire manufacturing process, from turning and grinding, and from welding right up to the concluding ultrasound testing process," Mootz says. "We can develop and construct the whole of the process chain. This significantly simplifies the planning of new production sites and the expansion of existing ones."

The ELC 250 DUO

The ELC 250 DUO - a compact laser welding cell for the machining of differential housings. The DUO variant features two spindles. The twin-station operation allows for cycle time-concurrent loading and unloading of the work spindles.

The general market development does play into the hands of the German machine builder: It is not only the successful dual-clutch transmission that ensures the need for more gears. Conventional transmission systems also tend to have more speed gears, as this reduces gas consumption and improves the driving comfort. "Having said that, we are offering a well proven welding technology that provides an energy-saving, high-precision manufacturing process and, at the same time, helps to advance lightweight construction and reduce production costs. This is no doubt a very successful and persuasive combination," concludes Mootz.

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