Press Release
Aachen,
September 29, 2011
Dual gloss: producing innovative surface
designs by laser remelting
The Fraunhofer Institute for Laser Technology ILT has
developed a method of structuring the metallic surfaces
of tool inserts by laser remelting. For the first time, this
method makes it possible to structure materials without
resorting to ablation and at the same time to polish them
to a brilliant gloss finish. This gives tool manufacturers
greater scope to adapt their production processes to
incorporate novel structures and design elements while
also saving them time and money. Another new
technique can additionally be used to provide tools and
products with a dual-gloss effect.
From steering wheels to toothbrush handles, we have
become accustomed to the look and feel of structured
surfaces on components we encounter in virtually all
areas of our lives. Injection molding tools made from
metal are often used to give these components their
structure, and one method that is commonly used to
produce the desired structure on the tools themselves is
photochemical etching, where specific regions of the tool
Fraunhofer Institute
for Laser Technology ILT
Marketing and Communications
Dipl.-Phys. Axel Bauer
Steinbachstraße 15
52074 Aachen
Phone +49 241 8906-194
Fax +49 241 8906-121
axel.bauer@ilt.fraunhofer.de
www.ilt.fraunhofer.de
insert are structured by etching away the unwanted
regions. However, this is a costly and time-consuming
process which requires the use and disposal of large
quantities of environmentally hazardous acids.
September 29, 2011
Page 2
A more environmentally-friendly alternative is the
technique of laser structuring by ablation, which has been
used successfully for more than ten years. This method
can achieve ablation rates of 1-10 mm3/min in processes
designed to create structures > 10 µm, but in many cases
the workpiece subsequently requires further treatment to
remove the melt residue which accumulates during
ablation. In addition, the laser requires some ten passes
to achieve a structure depth of 200 µm, which means that
the laser-based structuring of large surfaces through
ablation is generally not a cost-effective option for tool
manufacturers.
Remelting instead of ablation
Fraunhofer ILT has now developed a method of
structuring tools using laser remelting. The laser beam
travels over the workpiece and the resulting heat input
melts the metal surface. At the same time, the laser
power is modulated in order to continuously change the
size of the melt pool at defined points. »This modulation
causes the material to be redistributed, creating
mountains and valleys: half of the resulting structure lies
Fraunhofer Institute for
Laser Technology ILT
Marketing and Communications
Dipl.-Phys. Axel Bauer
Steinbachstraße 15
52074 Aachen
Phone +49 241 8906-194
Fax +49 241 8906-121
axel.bauer@ilt.fraunhofer.de
www.ilt.fraunhofer.de
above its initial level, while the other half lies below it,«
says André Temmler, project manager at Fraunhofer ILT.
Thanks to surface tension, when the uppermost layer of
the molten material solidifies, it exhibits uniformly low
roughness, and the surface is left with a brilliant polished
September 29, 2011
Page 3
finish. Unlike laser structuring by ablation, the novelty of
laser structuring by remelting is its ability to directly
produce finished surfaces which do not require any postprocessing. For a structure depth of approximately 200
µm, this method can achieve processing rates of up to
75 mm2/min, enabling a volume redistribution rate of 15
mm³/min in a single pass. A further advantage of this new
method is that it consumes less energy and fewer
resources than conventional laser-based structuring by
ablation. Less energy is required for melting than for
sublimation, the process requires significantly fewer
passes, and there is no loss of material. Depending on
the material and batch size, these benefits can yield
considerable time and cost savings for tool
manufacturers. For flat surfaces and single-curved
component geometries, the laser technique of structuring
by remelting is already available for industrial use.
Temmler and his team are now working on applying the
technique to freeform surfaces.
Dual-gloss effect by selective laser polishing
Fraunhofer Institute for
Laser Technology ILT
Marketing and Communications
Dipl.-Phys. Axel Bauer
Steinbachstraße 15
52074 Aachen
Phone +49 241 8906-194
Fax +49 241 8906-121
axel.bauer@ilt.fraunhofer.de
www.ilt.fraunhofer.de
In cases where an additional dual-gloss effect is required
for end products such as decorative elements or an entire
product surface, the first step is to apply a matt finish to
the whole surface of the tool, which is generally achieved
through blasting with glass beads or sand. Selected
September 29, 2011
Page 4
regions are then remelted using a laser beam. These
regions solidify from the melt with a polished finish – in
other words, the selective laser polishing creates a
contrast between the matt, untreated areas and the
brilliant, laser-polished areas. Depending on the intensity
of the dual gloss, this can even produce a 3D effect in
which the polished points appear to protrude from the
surface. One example of how selective laser polishing can
be used is to provide structured tools designed to apply a
leather grain structure to plastic components with a dualgloss effect which is then transferred to the end product
during the molding process. For the first time, this
selective polishing technique can now be applied on an
industrial scale for both flat and freeform surfaces.
Visitors to the joint Fraunhofer Booth C66 in Hall 11 at
EuroMold 2011 will have the opportunity to see
components produced with workpieces which were laser
structured by remelting. Our experts will also be
presenting a selection of sample objects molded in plastic
by selectively laser-polished tools.
Captions:
Fraunhofer Institute for
Laser Technology ILT
Marketing and Communications
Dipl.-Phys. Axel Bauer
Steinbachstraße 15
52074 Aachen
Phone +49 241 8906-194
Fax +49 241 8906-121
axel.bauer@ilt.fraunhofer.de
www.ilt.fraunhofer.de
Fig. 1: Surface with variable structures produced by laser
remelting.
Source: Fraunhofer Institute for Laser Technology ILT,
September 29, 2011
Page 5
Aachen.
Fig. 2: Dual gloss effect: molded plastic component
produced by a selectively laser-polished tool insert.
Source: Fraunhofer Institute for Laser Technology ILT,
Aachen.
Fraunhofer Institute for
Laser Technology ILT
Marketing and Communications
Dipl.-Phys. Axel Bauer
Steinbachstraße 15
52074 Aachen
Phone +49 241 8906-194
Fax +49 241 8906-121
axel.bauer@ilt.fraunhofer.de
www.ilt.fraunhofer.de
September 29, 2011
Page 6
Your contacts at the Fraunhofer ILT
Our experts are on hand to answer your questions:
André Temmler
Polishing
Phone +49 241 8906-299
andre.temmler@ilt.fraunhofer.de
Dr. Konrad Wissenbach
Additive Manufacturing and Functional Layers
Phone +49 241 8906-147
konrad.wissenbach@ilt.fraunhofer.de
Fraunhofer Institute for Laser Technology ILT
Steinbachstrasse 15
52074 Aachen
Phone +49 241 8906-0
Fax +49 241 8906-121
www.ilt.fraunhofer.de
Fraunhofer Institute for
Laser Technology ILT
Marketing and Communications
Dipl.-Phys. Axel Bauer
Steinbachstraße 15
52074 Aachen
Phone +49 241 8906-194
Fax +49 241 8906-121
axel.bauer@ilt.fraunhofer.de
www.ilt.fraunhofer.de