Laser based sandblasting with light

The Fraunhofer IWS has developed a laser technology to clean and structure surfaces in a particularly fast and environmentally friendly way. Instead of sand grains, high-energy light is used.

Sandblasting was yesterday. More precise, less expensive and more environmentally friendly than conventional systems, laser beams are suitable for cleaning and structuring surfaces. The Fraunhofer Institute for Material and Beam Technology IWS in Dresden has developed the "LIGHTblast" technology for this purpose and is now transferring it to the automotive supply industry, semiconductor manufacturing and other industries.

The Fraunhofer IWS researchers see considerable ecological and economic potential: "This is like sandblasting at the speed of light," explains Dr. Patrick Herwig, who heads the Laser Cutting Group at the institute. "We are thus enabling industry to process equipment and components faster, more environmentally friendly and cleaner than before. In addition, our process is less expensive than classic sandblasting when used in series production, considering the entire production chain. We are certain that laser technology will pay off for companies." The Fraunhofer IWS is currently preparing initial application examples with various end users. There, laser systems could soon gradually replace sandblasting systems.

The market potential is considerable. This is because the number of industries in which classic sandblasting systems are used is increasing. They not only remove any contamination from a wide variety of components, but also roughen them in a defined manner before coating, thus optimizing the result of the coating process. Occasionally, sand particles become lodged in the treated surface and remain as a defect even after intensive cleaning. In conventional processes, a jet of compressed air accelerates sand at high speed onto the surface to be treated. The sharp-edged sand particles tear away parts of the surface, wearing away the sharp edges and mixing with the resulting dust. With each use, the blasting medium becomes more contaminated and is steadily ground round. The process result continuously deteriorates. Ultimately, the mixture must be disposed of as hazardous waste, which pollutes the environment and causes additional costs. The Fraunhofer IWS uses high-energy light instead of sand grains to clean and roughen. For this purpose, researchers developed the laser-based process LIGHTblast, which realizes cleaning and structuring tasks significantly faster than conventional processes and should result in lower operating costs in series production. The process is also easier to automate with positive effects on quality, process control and occupational safety. In addition, the system works much more precisely than a sandblasting system, as a laser beam with a diameter of less than 50 micrometers (i.e. thousandths of a millimeter) replaces a particle stream several centimeters wide. "In a sense, we are working with a scalpel instead of a club," Patrick Herwig explains metaphorically. How rough the surface ends up can also be very finely adjusted with the new method.

Apart from the cost and quality benefits, the ecological balance of their manufacturing processes is becoming increasingly important for many industrial users. Not least, many pre- and post-processing steps are eliminated: light-based processing does not require any chemicals for cleaning. The laser blasting system precisely processes only the desired surfaces, consuming neither sand nor material for masking and thus saving hazardous waste and adhesive tape waste. The laser beam vaporizes parts of the surface, the expanding vapor carries away solid components and also achieves a defined roughness.

Several industrial companies have already recognized these and other advantages of light sandblasting. They now want to gradually transfer the technology into manufacturing practice together with the Fraunhofer researchers. For example, the Fraunhofer IWS is further developing the process with C4 Laser Technology to structure hard material coatings using laser technology and to decisively improve the finishing process with regard to costs and environmental compatibility. "Every brake disc is different," says René Bischoff, Chief Technology Officer at C4 Laser Technology from Freital near Dresden. "Factors such as the chemical material composition, cooling rates, the condition of the machining tools or the graphite structure near the surface are just a few parameters that exert a not inconsiderable influence on the coating process of gray cast iron surfaces. Together with the Fraunhofer IWS we have found a way to standardize the friction band surface condition of the brake disc blank before coating. In this way, we have succeeded in making the normalization process fully automatable and cost-effective, and in increasing process capability." As part of the production chain, the process thus contributes to an affordable brake disc whose significantly extended service life will ensure that less particulate matter is produced in road traffic in the future. Among other things, the Dresden institute is contributing its expertise in the design of laser-based manufacturing processes and in software development for process control.

In general, the new method can be used wherever components need to be cleaned, pre-structured or roughened for subsequent coating. Further development steps are planned for this purpose. (OM-5/23)