Researchers to optimise laser welding for 3D-printed plastics

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3D-printed sample component: The laser transmission of 3D printed plastic components depends on layer thickness and orientation. (Image: LZH)

Researchers are developing an ‘expert system’ that will optimise the 3D printing and subsequent welding of plastic components.

The system will support small and medium-sized enterprises (SMEs) by enabling them to weld 3D-printed plastic components without having to analyse each component in detail beforehand.

Laser transmission welding is already used to weld injection-molded plastic components together. For 3D printed parts however, cavities and boundary layers often prevent uniform welding. These cavities and boundary layers are individual to each component, because in additive manufacturing no two components are alike. Even components from the same series will have a different internal structure, despite being externally identical.

Addressing this issue is the therefore aim of the QualLa project (Quality assurance in laser welding of additively manufactured thermoplastic components), being undertaken by scientists at the Laser Zentrum Hannover (LZH) and the Institut für Integrierte Produktion Hannover (IPH). 

To develop their system, the researchers are analysing fused deposition modeling, a 3D printing process in which thin strands of molten plastic are superimposed layer by layer.

Even before the process starts, the researchers want their expert system’s software to provide recommendations on which material, which layer thickness, and which layer orientation are best suited to achieving the highest possible laser transmission. Thanks to this preliminary work, it will then be possible to optimally weld the printed components together.

In addition, the scientists want to develop a method to actively measure the laser transmission during welding. This will involve determining at which points the laser beam is transmitted, and to what extent, for each individual component. This data will then be used to control the laser welding process.

Fused Deposition Modeling, a 3D printing process where plastic components are built up layer by layer. (Image: IPH)

If the laser beam is transmitted less at a certain point on the component, the laser power will be increased. If the component is transmitted more at another point, the laser power will be lowered. The researchers' goal is to develop a process control system that adjusts the laser power as a function of transmission so that a uniform weld seam is produced – even if the 3D-printed component does not transmit the laser beam uniformly.

The scientists want to process the information using neural networks and machine learning. The system will then learn to recognise correlations between various input variables and the print result independently and thus predict the expected transmission.

LZH and IPH are working closely with industry on the research project, with the accompanying committee including companies from the fields of laser technology, additive manufacturing and plant engineering. The partners also welcome other companies to participate in the project – particularly those involved in artificial intelligence or additive manufacturing.

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