01 Feb 2021
German partners have developed roller process to efficiently repair and laser-coat components in production.EVEREST, involving the Fraunhofer Institute for Laser Technology and three industrial partners, has developed a process and system technology to efficiently repair and coat metal components.
An adaptation of the Fraunhofer ILT’s EHLA extreme high-speed laser material deposition process and, the new approach has been tested it on a roller system.
Now after successfully completing the project, the researchers in Aachen, Germany, are seeking to establish the new process chain in industry. The partners’ goal is to coat long and large rollers and other rotating components with the EHLA process in a near-net-shape.
Almost a decade ago, researchers at ILT started to develop high-speed laser material deposition, which increased the previous process from a maximum of two to several hundred meters per minute.
The ongoing collaborative project EVEREST involves industrial partners Lunovu from Herzogenrath, BCT from Dortmund, and Drink & Schlössers, from Krefeld, Germany. Alongside the Fraunhofer ILT scientists, they have together developed process parameters and strategies for coating and repair as well as for hybrid manufacturing of sealing surfaces.
This process has been successfully tested in practice. For example, a heating roller (length: 1,200 mm, diameter: 200 mm) was coated with corrosion-resistant powders based on iron, nickel and cobalt. The coating thicknesses in the project ranged from 50 to 300 µm – at process speeds of 20 to 200 m/min.
The system technology – developed by BCT and Fraunhofer ILT for geometry acquisition and process monitoring as well as for adaptive tool path planning – played a very important role in the project. To accomplish this task, the partners used a specially developed CAM module that corrects geometric deviations from the target state in a semi-automated manner.
“We took a camera-based approach that allows us to follow the coating process from a bird's eye view, and thus draw conclusions about the stability of the process,” said Gregor Bultel, a scientist at Fraunhofer ILT. “We are now looking for the first users for it.”
The practical tests were conducted in Herzogenrath at the project consortium leader Lunovu, which also supervised the EHLA demonstration system. This manufacturer of laser systems integrated the entire process chain into the demonstrator in order to integrate the complete workflow from scanning, path planning and automatic generation of the NC program into the automatic repair process.
“The biggest problem was to combine all the subsystems involved into one process chain,” said Lunovo application developer Andreas Bartling. “The result was a reliable process chain that not only saves resources, but also features efficient system technology requiring very few employees to look after.”
In the project, those involved also analyzed the need for further action. For Bultel, the upcoming work packages include optimizing the powder materials, depositing complex geometries, increasing the final contour proximity, and developing new process strategies for crack-free deposition of very hard coatings. Bultel added, “I'm thinking about linking process chains: We could also combine the coating process with post-processing steps – perhaps even in one and the same machine.”
The roll manufacturer Drink & Schlössers took over the practical testing. “With the process and the system technology used, the component surfaces could be processed well,” summarizes Managing Director Kurt Beckers.
“We were able to produce the surfaces exactly as we had imagined.” The managing director was already familiar with powder-based laser material deposition, so he was also very interested in the significantly faster version.
After the satisfactory pilot project, Beckers sees good opportunities for EHLA: He hopes that the process technology is developed even further, which will also allow very large, long rollers with a diameter of up to 3,000 mm to be reliably coated close to the final contour.
This project was supported by funds from the European Regional Development Fund.
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