Polygon scanner based ultra-short pulse laser processing in roll-to-roll manufacturing
Aim of the project
The overall objective of PoLaRoll project is to substitute the lithography step in current etching processes by directly structuring the lacquer with the PoLaRoll laser micro machining unit. The PoLaRoll-module will replace the current masking process within a continuous lithography etching process for micro-structuring stainless steel reels. This will enable a flexible and cost efficient process consequently increasing significantly the productivity . The modular concept of the laser structuring system will allow the integration into several other applications in order to substitute masking processes or direct digital structuring.
The focus of PoLaRoll is on the continuous and digital production process for structuring a lacquer film on a stainless steel web and thereby substitutes the need for a negative mask for imprinting the lacquer, which is making the current production process inflexible and expensive.
To achieve this ambitious goal, the development in PoLaRoll can be described through the following objectives:
- Objective 1: Development of a high performance laser source
The development of a high performance ultra-short pulsed laser source will focus on a huge improvement on the system’s pulse repetition rate and pulse energy, resulting in a pioneering overall optical power. This development will generate an industrial ultra-short pulsed laser source with never before presented specifications on industrial scale for high speed processing.
- Objective 2: Development of a high speed polygon scanner
Besides the increased specification levels of the laser source, the polygon scanner will be further improved to cope with the new high processing speeds and the high pulse repetition rates achieved. Additionally to this goal, a further major effort will be addressed to ensure a high accuracy over the high speed laser spot positioning based on the polygon scanning unit for the micro structuring process.
- Objective 3: Development of an in-line measurement for polygon scanner processing
To ensure a high precision for the material micro machining, two in-line measurement systems will be developed. On the one hand, the solution will address the direct measurement of the lacquer ablation results and therefore show insufficient material treatment in real-time. On the other hand the solution will measure the resulting micro structures and perform an inline evaluation of its form and position. Based on both units, a control and adaptation of the process will be implemented. This allows an automatic adjustment of laser and roll-to-roll process parameters and quality assurance.
- Objective 4: Laser based micro machining system with synchronisation between laser source and multiple polygon scanners
As previously stated, the project will result in highly improved laser source and polygon scanning units with huge achievable frequencies and speeds. Besides the synchronisation of laser source and one polygon scanner this generates further high requirements on the overall system synchronisation. In this context, the project PoLaRoll concentrates on the implementation of a highly innovative ultra-fast synchronisation unit for at least to polygon scanners operated with one laser source, which will allow the fully usage of all system specifications on real industrial context. This includes beam splitting and beam guiding to both sides of the web.
- Objective 5: Integration of laser based micro machining system for two sided laser structuring into a roll-to-roll process
A further objective is the integration of the final laser micro structuring system including the enhanced ultra-short pulsed laser source and polygon based scanning unit as well as the in-line measurement systems in the roll-to-roll system. The design and composition of the system is modular, this fact offers a high adaptability and therefore the laser source and polygon scanner are capable of being integrated in several roll-to-roll process chains. Hereby concrete actions regarding process synchronization (roll-to-roll and laser processing unit) as well as data exchange and product information will be in focus, to warrant modular and robust system integration on industrial standard.
- Demonstrator: Structured stainless steel with sieve geometry for solar shading applications
For the evaluation of the developed laser micro structuring module for individualised high speed roll-to-roll manufacturing, the developed module will be directly integrated into the end-users production line. The quality can be directly seen after the production process since all defects within the geometry result in an optical inhomogeneity. The field of application is within solar shading of glass facades. The geometry allows cutting the solar radiation and therefore reduces the energy used for cooling and ventilation. By changing the pitch between the etched holes on the front and the backside different refractive properties can be achieved and enabled through the individualised laser structuring process they can be placed on the same reel. Moreover the laser processing allows a higher production quality compared to state of the art production since transitions caused by the masking process are completely eliminated. To further improve the developed high throughput laser ablation process, a special chromate free lacquer formulation will be developed in order to achieve higher ablation rates with less energy per pulse.
Impact & Sustainability
When looking along the value chain of laser manufacturing systems, the laser sources typically are the starting point and are integrated into downstream machines and processing systems. To position the next generation Roll-to-Roll manufacturing technology in the global market place, time to market is a key factor. The PoLaRoll results will help Europe stay competitive on the international market of laser micro machining and roll-to- roll machinery solutions providing:
- Improved competiveness of laser-based manufacturing industry (equipment and suppliers) and the end-user industry
- Improved competiveness and strengthened Europe’s market position of laser-based manufacturing industry
- More efficient, more flexible and higher throughput of individualised laser-based production
Further impacts can be associated to PoLaRoll project:
- Environmental impacts: the partial replacement of environmental unfriendly chemicals on the etching process chain currently used on the foil perforation by laser based machining will lead towards a greener manufacturing. The partial replacement of unfriendly chemicals will generate environmental impacts on the reduction of this production as well as on the reduction of its waste management, which represents a direct economical aspect as well.