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Ultra high-power laser for welding of towers and foundations

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onsdag 31. oktober 2012

Reduced costs and increased speed in the production of wind turbine towers and foundations. Those are the main goals for Lindoe Welding Technology with its investment in a 32kW fiber laser system.

By Tea Tramontana

Lindoe Welding Technology, LWT, has ordered a very powerful laser system. The system consists of two separate disc lasers each of 16kW which can be combined to provide 32kW at the work-piece.

“We will make this powerful laser system available to external users such as industries and universities and it is, I believe, the only such open facility in the world”, says Christian Højerslev, CEO of LWT.

Although the main aim is to develop new production methods for the renewable energy sector, other industries who are considering introducing laser welding in their production or research are welcome at LWT, which will offer education and courses, consultancy and development of production method, Feasibility studies, designing, testing, evaluations, etc.

Lindoe Welding Technology provides an environment for development and innovation with focus on welding, cutting and surface engineering. The technological pivot is its 32 kW laser system. The photo shows both how well defined weld beads the laser produces, and how flexible the technique is with respect to work-piece geometry. Photo: TRUMPF

Focusing on efficiency
32 kW is a large laser power, which will be focused at the workpiece during welding of really thick walled plates. Often, only a smaller part of the power will be needed, permitting LWT to work with process optimization instead. You can say that companies producing with a 4kW laser today will be able to carry out production as much as eight times faster with the LWT laser system.

Christian Højerslev, CEO at LWT. Photo: LWT

“Laser welding opens the possibility of cutting the processing time by up to 20 times and cutting the cost by at least half, and therefore our laser system has the potential to become a game changer,” says Christian Højerslev. Highlighting the need for efficiency in the wind turbine industry, the CEO gives an example:

”The tower is by far the single most expensive part of a wind turbine, and its relatively simple geometry makes it a suitable candidate for laser welding, which has substantial potential for reducing wind turbine tower production costs”.

Cooling rate – the greatest challenge
One of the greatest laser welding challenges in relation to the thick walled plates of 15 millimeters or more will be the cooling rate, which might be thousands of degrees per second. This causes high thermal gradients in the material during welding, which is why embrittlement, cracking and formation of pores during cooling is likely to occur – unless proper action is taken to avoid this.

When it comes to the welding of large structures such as wind turbine towers or foundations, another great challenge will be narrow tolerances, i.e. being able to prepare the joining faces for welding in a manner that ensures sufficient precision, which is a must when using laser welding.

“Though the challenges are considerable the possible gains are even greater and industry is already showing interest in working with us when we are ready by 1st of January 2013”, says Christian Højerslev. Customers are driven by many different needs:

“Some have a need for increased efficiency. Some are mainly interested in actual research and development activities and a third group of customers sees the technology as a development that will ensure them a competitive advantage in the years to come.”




Facts:


LWT ‘s laser system
LWT’s laser system consists of two separate disc lasers, each of 16kW. Each of the two 16 kW lasers uses a transport fiber to deliver the laser beam to the work piece. This gives a high flexibility with respect to processing with the lasers, a flexibility, which among others makes them suited for robotic welding. The two lasers can be combined via a special transport fiber and thereby deliver up to 32kW to the work-piece. The laser beam has a wavelength of 1030 nm and each of the two 16 kW lasers has very good beam quality – the beam parameter product, BPP, is 8 mm*mrad. (BPP is the product of a beam’s half divergence angle and the radius of the beam at its narrowest point, measured in milliradians multiplied by millimeters, ed.)

LWT’s laser system can deliver a very focused power – about 1MW/mm2. Such a concentration of energy causes local temperature rises of several thousand degrees in fractions of a second on interaction with the material. Thus, the material experiencing such thermal exposure will not melt but evaporate i.e. forming metal gases or even charged plasmas.

The approximately 1MW/mm2 that LWT’s laser system can deliver to the work-piece is comparable to the power generated by electron beam welding. But in contrast to processing with electron beams, laser beams do not require a vacuum nor nor will the laser induced plasma radiate harmful X-rays.

Lindoe Welding Technology
Lindoe Welding Technology’s initial focus is on welding; and the technological pivot is its 32kW laser system. Moreover, LWT offers access to equipment and knowledge for classical welding technologies such as MIG, MAG, TIG and SAW.

In addition to welding, LWT provides assistance and services in the fields of cutting and surface engineering. Situated at Lindø Industrial Park, LWT provides an environment for development and innovation in the form of realistic – and full scale – production facilities.

LWT is established as a partnership between FORCE Technology, a member of the GTS – Advanced Technology Group and LORC, Lindoe Offshore Renewables Center.
Visit LWT at www.lwt.dk

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