Surface functionalisation is present in a wide range of sectors, however when considering the application of such functionalisation in complex industrial parts, several challenges must be faced. The difficulty of reaching all surfaces of complex 3D parts is significative, especially in those with considerable size and weight. At the same time, as current regulations do not cover parts with functionalised surfaces, uncertainty about the regulatory compliance of such parts in some sectors makes a straightforward integration of this process more difficult. As a result, this limits the potential of some companies in terms of opening up new markets or attaining a competitive edge. Additionally, the creation of functional surfaces has traditionally relied on processes such as chemical reactions and/or the complete coating of the native surfaces (e.g. aerofoils). Due to their very nature, these processes generate unwanted by-products thereby leaving a significant environmental footprint, which go against the “do no significant harm” principle of The European Green Deal. In order to avoid these setbacks, a new functionalising process for complex 3D shaped parts in which the environmental footprint is reduced and where new guidelines are generated to complement the manufacturing standards of target sectors, could be a game changer.
Among the different methods available for surface functionalisation, designs inspired by nature have been able to enhance functionalities such as hydrophobicity, surface self-cleaning, surface anti-freezing, etc. Specifically, nano- and micro-structured surfaces mimicking shark skin (so-called riblet surfaces) have been shown to significantly reduce the frictional resistance of flat surfaces .
Work already exists based on aforementioned riblet microstructures to reduce aerodynamic drag of 3D parts. However, the design and application of riblets on highly rotating parts such as fan wheels or hydro turbines is still a major challenge today, as the dimensions of the riblets should ideally change continuously on the surface of these objects, and the commonly used adhesive foils including the riblet coating cannot meet this requirement. To overcome this challenge, laser structuring is a highly attractive alternative to produce tailor-made riblets with a continuously variating cross-section. An additional advantage of laser structuring is its versatility, which enables it to tackle the generation of a wide variety of nano- and microstructures on a wide range of parts of different sizes and shapes.
BILASURF aims at developing and integrating a process for high-rate laser functionalization of complex 3D surfaces using tailored designed riblets to reduce friction and improve the environmental footprint of industrial parts, ensuring a high throughput with the help of inline monitoring capabilities. This solution will provide European industry with a key tool to use a more efficient and environmentally friendly manufacturing process.
The project includes innovation in different areas: design and simulation of bio-inspired functional surfaces, precision laser tooling, manufacturing integration, inline monitoring and new manufacturing guidance, with the goal of forming the manufacturing path.
The laser processes to be developed in the project need to be robust to be able to process large, complex shaped 3D parts. At the same time, one of the final goals is to generate tools to expand the technology to multiple sectors (in addition to the ones targeted with the final demonstrators). Therefore, several laser technologies are being explored during the project: two Laser Surface Texturing (LST) techniques, Direct Laser Interference Patterning (DLIP) and Direct Laser Writing (DLW), and microcladding (μCLAD).
In-line monitoring of laser processes and manufactured parts is essential in this project to demonstrate process stability and to optimize reproducibility and quality of manufactured parts. An innovative approach for laser surface structuring is acoustic emission analysis that has been harnessed to evaluate the process condition and detect process deviations. In BILASURF, the challenge is to design a combined system based on acoustic emission (high temporal resolution) and vision-based metrology (high spatial resolution).
The technology developed during the project will be validated in two use cases that will benefit from it: hydropower turbines and industrial fan wheels. The goals for the end users are the following: Efficiency improvement, surface texturing variability reduction and strengthening the market position.
