A laser for divers
05/03/2017

Figure 1: Laser cutting of sheet piling under water. (Photo: LZH)

Figure 2: Metal sheets can be cut underwater by using a laser. (Photo: LZH)

Figure 3: The LZH has developed a laser cutting process for use underwater. (Photo: LZH)

Working under water is personnel- and time-intensive. The Laser Zentrum Hannover e.V. (LZH) is therefore working on developing a laser-based, automated process for cutting sheet piling under water, together with the Institute of Materials Science of the Leibniz Universität Hannover.

Sheet piling protects fortified shore areas, or can be used to dry out these areas if repairs are necessary. If the sheet piling must be dismantled, divers must cut the walls into smaller pieces using a cutting torch. Normally, a diver can cut about 20 meters a day, which corresponds to a speed of about 0.07 meters per minute. In the project LuWaPro, scientists at the LZH have now developed a process which uses a disc laser for torch cutting. The divers thus only carries out a supervisory role. The process can be used to separate the metal sheets, which are usually 10 mm thick for sheet piling, at speeds of up to 0.9 m/min.

Robust process despite unfavorable conditions
Poor visibility, currents or uneven surfaces make working underwater more difficult. The scientists of the Underwater Technology Group achieved a position tolerance of about two millimeters in their process, enabling the system to react robustly to possible impacts during underwater operation. The process was tested with two scenarios: On the one hand, standalone metal sheets were cut underwater, on the other hand, the sheets were backfilled with concrete. In the second scenario, a leaking of the molten material through the cutting kerf is achieved by tilting the laser head at an angle of 20 degrees.

Through cuts?
A further major advantage in comparison to the hand-guided process is the possibility of monitoring the process. Sensors reliably determine whether a cut is completed or not. Otherwise the diver often cannot see this due to the poor visibility underwater.

Safe laser cutting under water
The laser safety necessary for this process can be guaranteed if the diver wears conventional safety goggles under the helmet.

The project “Laser cutting under water for high productivity – LuWaPro” was supported by the Federal Ministry for Economic Affairs and Energy.

Three figures and one video are available for this press release.

 

Video: Demonstration of laser cutting at the Unterwassertechnikum (underwater technical center) Hannover (UWTH) (Video: Laser on demand GmbH)

 

Laser Zentrum Hannover e.V. (LZH)

As an independent, non-profit research institute, the Laser Zentrum Hannover e.V. (LZH) stands for innovative research, development and consulting. The LZH is supported by the Lower Saxony Ministry for Economics, Labour and Transport and is dedicated to the selfless promotion of applied research in the field of photonics and laser technology. Founded in 1986, over 170 employees are now working for the LZH.

The focus of the LZH lies on the fields of optical components and systems, optical production technologies, and biomedical photonics. Interdisciplinary cooperation between natural scientists and mechanical engineers makes innovative approaches to challenges from the most different areas possible: from the development of components for specific laser systems to process developments for the most diverse laser applications, for example for medical technology or lightweight construction in the automotive sector. Seventeen spin off companies have emerged from the LZH up to now. Thus, the LZH has created a strong transfer between fundamental science, application oriented research, and industry.