Hybrid sensing for understanding of laser welding technology for process control (Hy-Las)
Antonio Ancona. To: University West From: CNR - Institute for Photonics and Nanotechnologies, Italy.
The project aims in strengthening the international networking within automation of laser beam welding (LBW) and additive manufacturing (AM) by facilitating for mobility between two strong research environments within the innovation-intensive "Sustainable production" area. This networking is expected to give both parts a more profound knowledge and thereby solve complex welding problems, both during the project and afterwards.
The aim of the project is to increase automation possibilities in existing industrial laser welding technology cells. Such increased automation would contribute to sustainable manufacturing and increased flexibility in laser welding industries. Laser processing, like LBW and laser metal wire deposition (LMD-w) are today suffering from robust monitoring and control, thus hindering from exploiting their full value. Laser welding comprises a number of benefits relative the more wide spread arc welding technologies like less heat input and thereby lower deformations and more means to control the heat input. However, the sensing system equipment for monitoring is not yet robust enough to be tractable for industry. The project will develop hybrid sensor systems with enough capacity to reliably monitor the ongoing process and thereby increase the understanding of the underlying physics. This is where Dr Ancona and his knowledge and experience will play an important role in cooperation with the industrial and scientific knowledge from University West researchers at Production Technology West (PTW), a research environment with modern industrial standard laser welding equipment and ongoing research projects with laser welding regional industries, today mainly with aeronautics focus.
Project Result Summary
The Hy-Las project aimed at developing a hybrid sensing system for monitoring laser based processes of great interest for the manufacturing industry such as Laser Beam Welding and Metal Additive Manufacturing. These processes are today suffering from the absence of robust monitoring and control Systems, so that post-process inspection techniques are often employed to assess the product quality. The "Hy-Las" approach relied on combining the information acquired by different sensors, i.e. a camerabased vision system, a spectrometer and photodiodes, to get a physical understanding of the process dynamics and detect in real-time deviations from optimal process conditions. All the sensor technologies employed in the project were non-invasive, non-contact, on-line, robust, cheap and easily integrable in a typical industrial laser-based manufacturing system, thus being very attractive for the University West industrial research partners like GKN Aerospace and Permanova.
The most relevant results of the Hy-Las project are:
- The development of a dual vision and spectroscopic monitoring system, consisting of a Camera with suitable Illumination and matched optical filters and a fast miniature spectrometer, which enables, through suitable Image and Signal processing algorithms, to detect the joint position and any misalignment of the laser beam from it. This system was demonstrated to work successfully even in the case of narrow gap butt welds, where the gap size is dose to zero (<0.1 mm) and most of the existing joint tracing Systems fall. Such a result is the base for the future development of a novel robotized control System to avoid lack of sidewall fusion is laser beam butt welds. This type of defect can hardly be noticed by ocular inspections, since they are often hidden by fused metal both on the top and root side of the weld, and is furthermore problematic to detect by non-destructive testing.
- The real time detection of alloying elements vaporization, by absorption and emission optical spectroscopy, during laser based metal additive manufacturing processes. Such a result is relevant to control and assess the chemical composition of the feedstock material and of the build during AM processes that would, indeed, affect the mechanical and corrosion resistance properties of AM manufactured metallic parts.
The Hy-Las project results have been presented and disseminated in several international scientific journal and Conference proceedings papers.
Thanks to the Hy-Las project a long term collaboration between University West (Sweden), CNR-Institute for Photonics and Nanotechnologies (Italy) and University and Politecnico of Bari (Italy) have been established. During the project, two Italien Master students and a post-graduate fellow had the chance to join the research activities at University West within the Erasmus traineeship program. A long term agreement for the exchange of PhD students has been signed between University West and University of Bari and two project proposals have been submitted for the continuation of the research collaboration between the Italien and Swedish academic institutions.
Finally, the Hy-Las project has been very beneficial for the career development of prof. Antonio Ancona, not only for the research results achieved but also for the enhancement of his teaching and supervising experience gained in the international industrial and research environment at the Production Technology West.