Präzisionserhöhung beim Laserstrahl-Mikroschweißen durch angepasstes Energiemanagement

  • Increased precision in laser beam microwelding using an adapted energy management

Häusler, André; Poprawe, Reinhart (Thesis advisor); Bobzin, Kirsten (Thesis advisor)

1. Auflage. - Aachen : Apprimus Verlag (2021)
Book, Dissertation / PhD Thesis

In: Ergebnisse aus der Lasertechnik
Page(s)/Article-Nr.: 1 Online-Ressource (IX, 112, XIII Seiten) : Illustrationen, Diagramme

Dissertation, RWTH Aachen University, 2020

Abstract

The increasing electrification of automobiles and daily objects requires a large number of joints to electrically and thermally highly conductive materials such as copper. In addition to resistance or ultrasonic welding, joining with laser radiation is a highly automated, contactless and reproducible joining technology, which can be used flexibly for different applications or designs. The industrial laser beam sources available for this purpose work in the wavelength range λ ≈ 1 µm, in which copper-based alloys have a low absorption coefficient, which can lead to an unstable energy input and thus to process disturbances. However, in order to realize a stable deep welding process for the contacting technique, a material-dependent intensity is required, which can be achieved either by reducing the focus diameter or by increasing the laser power. Due to a higher energetic load, the latter leads to damage of thermally sensitive components. Smaller focus diameters in turn lead to smaller connection cross-sections, which are disadvantageous for electrically conductive applications. To compensate for process instabilities and small connection cross sections, the use of a spatial and temporal power modulation in laser microwelding offers new degrees of freedom with regard to the design and quality of the resulting joints. The term local power modulation refers to a circular superposition of the linear feed, which results in a spiral path movement of the laser beam, whereas the temporal power modulation leads to a continuous change of the laser power over the process time. In addition to the process fundamentals, the influences of the individual compensation methods on the efficiency and precision of a laser beam micro-welding process are investigated both experimentally and simulatively in the course of this work. The efficiency is defined as the quotient of molten volume and laser power, whereas the precision is quantified with the help of the parameters welding depth constancy and seam surface roughness. By measuring the energy input during the joining process with high temporal and spatial resolution and a combined use of spatial and temporal power modulation, this paper provides a basic understanding of the process for influencing the precision and efficiency of laser microwelding of copper-based alloys.

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