Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Goodbye Absorbers: High-Precision Laser Welding of Plastics

10.07.2020

In the successfully completed NRW project SeQuLas, the Fraunhofer Institute for Laser Technology ILT and three industrial partners have developed a joining process that can be used to produce the smallest weld seams in transparent plastic components. The process makes use of a thulium fiber laser, which offers a particular advantage: Since plastics absorb the corresponding wavelength well, the process does not require additional absorbers such as soot. The process is particularly interesting for medical technology, as it should be used to increase flexibility and efficiency in industrial production.

In the life science sector, microfluidic chips have proven their worth since they can transport, mix and filter even the smallest amounts of liquid efficiently. They still pose a major challenge, however: the media-tight encapsulation of the microchannels integrated in the chips.


In the SeQuLas research project, the partners developed an electronically monitored process for gentle, high-precision laser transmission welding of small plastic components for medical technology.

© Fraunhofer ILT, Aachen, Germany


With the developed joining process, in which a thulium fiber laser is used, high-precision welding of microfluidic components can be achieved.

© Fraunhofer ILT, Aachen, Germany

Conventional joining technology reaches its limits in the micrometer range. In its place, absorber-free laser transmission welding (LDS) – with beam sources in the near-infrared (NIR) range – allows high precision and flexibility, making it the ideal solution here.

Transparent components thanks to the absence of absorbers

And that is why Fraunhofer ILT launched the SeQuLas project in 2017, together with Amtron GmbH from Aachen, Ortmann Digitaltechnik GmbH from Attendorn and Bartels Mikrotechnik GmbH from Dortmund.

The project was funded under the »Produktion.NRW« program of the LeitmarktAgentur NRW, and the acronym SeQuLas stands for »segmental quasi-simultaneous laser irradiation«. Here, a thulium fiber laser with an emission wavelength of 1940 nm was used as the beam source; plastics have a natural absorption in this wavelength range.

Since additional absorber material such as soot is not necessary, the transparency of the chip is not affected during laser processing.

However, this form of absorber-free laser transmission welding has a problem: Volume absorption creates a heat-affected zone (HAZ) that extends vertically over the entire cross-section of the component. The thermal expansion during the melting process promotes the formation of blowholes and cracks, which cause leaks in the seam structure. In addition, there is a risk that the material will warp, especially in flat components.

Quasi-simultaneous irradiation for gentle heating of materials

Quasi-simultaneous irradiation can be used to reduce the heat-affected zone from expanding vertically. In this process, a laser beam is guided several times along the weld contour at high speed with the aid of a scanner system: Thanks to this, the entire seam contour is heated simultaneously, which otherwise only melts sequentially in contour welding.

In tests with polycarbonate components, Fraunhofer ILT has demonstrated that during the welding process the heat is dissipated at the outer surfaces while heat accumulates inside the material. The increasing number of passes and the high scanning speed even reduce the vertical expansion of the heat-affected zone by up to 30 percent compared to contour welding.

Early detection of thermal damage

In a second step, the project partners developed a process control for the laser welding process. A pyrometer integrated in the beam path measures the temperature in the component during the welding process. By coupling the measurement signal with the position of the scanner mirrors, they have made it possible to record the heat distribution in the component in a spatially resolved manner.

In this way, thermal damage can be recorded and precisely localized during the welding process. The newly developed welding process can, therefore, react quickly to temperature deviations and control the laser power accordingly. In this way, homogeneous seam properties along the seam contour can be ensured.

The project »SeQuLas - Laser Welding of Absorber-Free Thermoplastics by Segmental Quasi-Simultaneous Irradiation« was completed in February 2020 and ran for three years. It was funded by the European Regional Development Fund (ERDF) and the state of North Rhine-Westphalia.

Wissenschaftliche Ansprechpartner:

M.Sc. M.Sc. Phong Nguyen
Micro Joining Group
Telephone +49 241 8906-222
phong.nguyen@ilt.fraunhofer.de

Dr.-Ing. Alexander Olowinsky
Micro Joining Group
Telephone +49 241 8906-491
alexander.olowinsky@ilt.fraunhofer.de

Weitere Informationen:

http://www.ilt.fraunhofer.de/en

Petra Nolis M.A. | Fraunhofer-Institut für Lasertechnik ILT

More articles from Materials Sciences:

nachricht Machine learning methods provide new insights into organic-inorganic interfaces
04.08.2020 | Technische Universität Graz

nachricht Unusual electron sharing found in cool crystal
31.07.2020 | Nagoya University

All articles from Materials Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: New Strategy Against Osteoporosis

An international research team has found a new approach that may be able to reduce bone loss in osteoporosis and maintain bone health.

Osteoporosis is the most common age-related bone disease which affects hundreds of millions of individuals worldwide. It is estimated that one in three women...

Im Focus: AI & single-cell genomics

New software predicts cell fate

Traditional single-cell sequencing methods help to reveal insights about cellular differences and functions - but they do this with static snapshots only...

Im Focus: TU Graz Researchers synthesize nanoparticles tailored for special applications

“Core-shell” clusters pave the way for new efficient nanomaterials that make catalysts, magnetic and laser sensors or measuring devices for detecting electromagnetic radiation more efficient.

Whether in innovative high-tech materials, more powerful computer chips, pharmaceuticals or in the field of renewable energies, nanoparticles – smallest...

Im Focus: Tailored light inspired by nature

An international research team with Prof. Cornelia Denz from the Institute of Applied Physics at the University of Münster develop for the first time light fields using caustics that do not change during propagation. With the new method, the physicists cleverly exploit light structures that can be seen in rainbows or when light is transmitted through drinking glasses.

Modern applications as high resolution microsopy or micro- or nanoscale material processing require customized laser beams that do not change during...

Im Focus: NYUAD astrophysicist investigates the possibility of life below the surface of Mars

  • A rover expected to explore below the surface of Mars in 2022 has the potential to provide more insights
  • The findings published in Scientific Reports, Springer Nature suggests the presence of traces of water on Mars, raising the question of the possibility of a life-supporting environment

Although no life has been detected on the Martian surface, a new study from astrophysicist and research scientist at the Center for Space Science at NYU Abu...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

“Conference on Laser Polishing – LaP 2020”: The final touches for surfaces

23.07.2020 | Event News

Conference radar for cybersecurity

21.07.2020 | Event News

Contact Tracing Apps against COVID-19: German National Academy Leopoldina hosts international virtual panel discussion

07.07.2020 | Event News

 
Latest News

Manifestation of quantum distance in flat band materials

05.08.2020 | Physics and Astronomy

Discovery shows promise for treating Huntington's Disease

05.08.2020 | Health and Medicine

Rock debris protects glaciers from climate change more than previously known

05.08.2020 | Earth Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>