ThyssenKrupp Magazin

Laser imprint without tolerance
sun, they achieve a level of precision that cannot be achieved by humans but only by
sensor-controlled machines. Human beings have not become superfluous, but their
function is reduced to controlling the process taking place before their eyes in the
control room.
Kahl offers a technically precise definition: “We use special types of steel with a
specific chemical make-up. The laser’s imprint on these types of steel is highly compromised
in a tiny amount of space.” What that means is that shrinking is hardly noticeable
and that the cooling speed is extremely high; increases in hardness are almost
imperceptible. The highly concentrated laser beam causes a minimal thermal
burden, which also minimizes the warping of the steel sheet.”
Kahl has a plethora of impressive comparisons up his sleeve. Next to each other
are joints and profiles, several of them welded using traditional welding equipment
and the other using laser technology. It is as though one was done by a butcher, the
other by a surgeon. The traditional seam is uneven and rough, the laser-welded seam
delicate and even artistic.
THE STATE-OF-THE-ART FACILITY FOR PRE-ASSEMBLY
So is all of this new? Kahl admits that the shipbuilding industry needed many more
years to implement laser technology than did other sectors, such as automotive production,
which long ago adapted it to its needs. Research institutes and universities
did pioneering development work, and Blohm + Voss took the results and built “what
is currently the state-of-the-art facility for pre-assembly work,” according to Kahl.
“The components of maximum dimensions, 4 x 12 meters, weigh around 9 tons.”
Imagine that the beams weighed 16 tons, and the overlying component parts an
additional 10 tons. The laser facility requires flying optics with a fixed portal and three
moveable work pieces as well as a positioning and a stretching portal. The laser-beam
sources, in contrast, are stationary. Kahl stresses one effect: the quality of welding pro-
I-seam on T-end, then simultaneously
laser-welded – that’s how the profiles end
up on the steel plate. The deep-welding
effect achieves a full attachment between
plates and ribs. “You won’t find a more
stable welding seam,” says Alfred Kahl,
head of shipbuilding at Blohm + Voss.
TK Magazine | 1 | 2004 |
LASERS 87
files on coated steel plates. The expert knew immediately:
I-seam on T-end, simultaneously laser welded: that’s what
it’s about, and Kahl produces some pictures and charts
that illustrate the difference compared to conventional fillet
welds. While this method only joins the corners, the lasers
work much more intensely on the materials.
“With the deep-welding effect, we achieve a full attachment
between plates and ribs,” says Kahl. “You won’t
find a more stable welding seam. Germanische Lloyd has
certified this technology for us.”
A surgeon’s precision for products whose surfaces
can cover a whole field – that is the attractiveness of laser
technology in shipbuilding. With this, following Kahl’s
words, lightweight construction has finally made it into the
world of “fast ships.” When you think that each ship can
have 200 kilometers, or about 125 miles, of laser-beam
seams spread across an area of 60,000 square meters,
you can imagine the powerful dimensions. “The laser will
take care of it,” you might be tempted to say. But what
does that mean? Here nothing has to be straightened
warm or with a flame, since angle shrinkage, buckling and
bending are things of the past.
When the laser does its blindingly bright work on the
panels, everything fits to a T. But when it comes to tolerance,
the laser doesn’t give any slack. Because tolerance
and precision production are two things that don’t fit together.
Not one little bit. 7