Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Dual gloss: producing innovative surface designs by laser remelting

29.09.2011
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.


Fig. 1: Surface with variable structures produced by laser remelting. Fraunhofer Institute for Laser Technology ILT, Aachen.


Fig. 2: Dual gloss effect: molded plastic component produced by a selectively laser-polished tool insert. Fraunhofer Institute for Laser Technology ILT, Aachen.

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 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.

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 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 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 post-processing. 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

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 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 dual-gloss 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.

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

Axel Bauer | Fraunhofer-Institut
Further information:
http://www.ilt.fraunhofer.de

Further reports about: ILT information technology laser beam laser system production process

More articles from Trade Fair News:

nachricht COMPAMED 2017: New manufacturing processes for customized products
06.12.2017 | IVAM Fachverband für Mikrotechnik

nachricht SYSTEMS INTEGRATION 2018 in Switzerland focuses on building blocks for industrial digitalization
20.11.2017 | IVAM Fachverband für Mikrotechnik

All articles from Trade Fair News >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Towards data storage at the single molecule level

The miniaturization of the current technology of storage media is hindered by fundamental limits of quantum mechanics. A new approach consists in using so-called spin-crossover molecules as the smallest possible storage unit. Similar to normal hard drives, these special molecules can save information via their magnetic state. A research team from Kiel University has now managed to successfully place a new class of spin-crossover molecules onto a surface and to improve the molecule’s storage capacity. The storage density of conventional hard drives could therefore theoretically be increased by more than one hundred fold. The study has been published in the scientific journal Nano Letters.

Over the past few years, the building blocks of storage media have gotten ever smaller. But further miniaturization of the current technology is hindered by...

Im Focus: Successful Mechanical Testing of Nanowires

With innovative experiments, researchers at the Helmholtz-Zentrums Geesthacht and the Technical University Hamburg unravel why tiny metallic structures are extremely strong

Light-weight and simultaneously strong – porous metallic nanomaterials promise interesting applications as, for instance, for future aeroplanes with enhanced...

Im Focus: Virtual Reality for Bacteria

An interdisciplinary group of researchers interfaced individual bacteria with a computer to build a hybrid bio-digital circuit - Study published in Nature Communications

Scientists at the Institute of Science and Technology Austria (IST Austria) have managed to control the behavior of individual bacteria by connecting them to a...

Im Focus: A space-time sensor for light-matter interactions

Physicists in the Laboratory for Attosecond Physics (run jointly by LMU Munich and the Max Planck Institute for Quantum Optics) have developed an attosecond electron microscope that allows them to visualize the dispersion of light in time and space, and observe the motions of electrons in atoms.

The most basic of all physical interactions in nature is that between light and matter. This interaction takes place in attosecond times (i.e. billionths of a...

Im Focus: A transistor of graphene nanoribbons

Transistors based on carbon nanostructures: what sounds like a futuristic dream could be reality in just a few years' time. An international research team working with Empa has now succeeded in producing nanotransistors from graphene ribbons that are only a few atoms wide, as reported in the current issue of the trade journal "Nature Communications."

Graphene ribbons that are only a few atoms wide, so-called graphene nanoribbons, have special electrical properties that make them promising candidates for the...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Innovative strategies to tackle parasitic worms

08.12.2017 | Event News

AKL’18: The opportunities and challenges of digitalization in the laser industry

07.12.2017 | Event News

Blockchain is becoming more important in the energy market

05.12.2017 | Event News

 
Latest News

Making fuel out of thick air

08.12.2017 | Life Sciences

Rules for superconductivity mirrored in 'excitonic insulator'

08.12.2017 | Information Technology

Smartphone case offers blood glucose monitoring on the go

08.12.2017 | Information Technology

VideoLinks
B2B-VideoLinks
More VideoLinks >>>