New laser welding process creates watertight seals

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A group of engineers has developed a new laser welding process that can be used to create water-tight seals, even in difficult to weld materials such as die-cast aluminium.

The engineers, from Fraunhofer IWS and Maschinenfabrik Arnold, believe the new process could be an attractive solution for medium-sized automotive suppliers and many other industrial customers.

In electric vehicles, the batteries and other electrical control devices have to be cooled. However, the electrical system must not come into contact with the cooling water, otherwise short circuits will occur. For this reason, control units are often protected by housings made of lightweight die-cast aluminium, which are then made watertight by encapsulating them with screwed-on covers and plastic seals.

While applying these covers and seals is often laborious, this must be done as it has not previously been possible to weld die-cast aluminium reliably enough to be watertight. This is due to gas-filled cavities being present in the material. When a conventional laser process cuts these cavities, the effect is similar to an abruptly opened balloon: the enclosed gas suddenly escapes from the cavity and simultaneously ejects the molten metal just produced by the laser. If the seam cools down in this state, defects remain that enable water to eventually reach the electrical system through small leaks.

Using their new laser process however, named ‘remoweldFLEX’, the engineers have now been able to achieve uniform, watertight welds in die-cast aluminium.

The process employs laser scanners, mirror optics, real-time controls and other system components in a processing head to produce an oscillating laser beam with a diameter of one tenth of millimetre. The beam is directed precisely and quickly along the desired contours of the die-cast aluminium, and is oscillated several thousand times per second in the molten bath. This results in very uniform and, above all, watertight weld seams. For real-time quality control purposes, the equipment can also be coupled with high-speed cameras. It also records sensor data during the welding process.

Using a laser instead of screws and plastic to seal batteries and electrical control devices in electric vehicles should significantly improve the service life and reliability of the vehicles’ cooling systems.

‘We have thus developed a very attractive solution for medium-sized automotive suppliers and many other industrial customers,’ remarked Dr Dirk Dittrich, who heads the Laser Beam Welding group at Fraunhofer IWS.

Industry 4.0

The ‘remoweldFLEX’ technology also offers an important step towards industry 4.0, according to the engineers.

‘Laser welding processes enable a very high degree of automation compared, for example, to screwing’, explained Dittrich.

This closes digitisation gaps in production. For example, it is difficult to translate the operator’s work steps trying to manually seal a connection pipe into computer-comprehensible values.

A laser welding head, on the other hand, works digitally. Users can obtain digital component files from the read-out process data. These detailed electronic documentations are in ever-increasing demand in more and more industries in order to achieve consistently high manufacturing quality in mass production.

‘Huge progress is possible here thanks to our procedures,’ Dittrich concluded.







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