Product Code: ICA13_M603

Remote Micro Welding with Multi-Mode and Single-Mode Fiber Lasers – a Comparison
Authors:
Andreas Patschger, Ernst-Abbe-Fachhochschule Jena; Jena Germany
Michael Guepner, Ernst-Abbe-Fachhochschule Jena; Jena Germany
Jens Bliedtner, Ernst-Abbe-Fachhochschule Jena; Jena Germany
Jean Pierre Bergmann, Technische Universitaet Ilmenau; Ilmenau Germany
Presented at ICALEO 2013

Both, multi-mode and single-mode lasers are well established in welding applications. In micro welding, single-mode lasers are often used while multi-mode lasers are more common regarding welding tasks in macro range. However, multi-mode lasers provide several advantages. Focal shifts due to high peak intensities on beam shaping optics can be avoided. Additionally, multi-mode lasers are operated with a removable transport fiber while single-mode lasers have to work with their inseparable feeding fiber, which is furthermore limited in its length. This can lead to a longer shutdown of the entire operating system in case of fiber damages due to back reflections or dust contaminations. On the opposite, the multi-mode systems are technically limited to relatively wide beam diameters and, therefore, appear inapplicable in terms of micro welding. But there are scaling effects which lead to another thermo-mechanical behavior in micro welding. Micro welding is a very fast joining process with velocities in the range of a few m/s. Because of the short laser/material interaction time and the large surface in comparison to the volume of the joining partners, the melt cools down and solidifies very quickly. Additionally, in micro scales the adhesion force between melt and ground material and the cohesion force in the liquid phase dominate the gravitation. These are the reasons why in micro welding bigger aspect ratios can be achieved compared to macro welding. These effects allow the application of multi-mode lasers in micro welding as an alternative to single-mode lasers. In this work, a 500 W multi-mode and a 1000 W single-mode fiber laser have been compared concerning their practicability in terms of micro welding. For this reason, stainless steel foils in thicknesses of 25 µm and 50 µm have been overlap welded with focal diameters between 22 µm and 204 µm using 2D scanning systems. The process boundaries have been carried out and process behavior has been determined by examining welding regime, melt flow induced seam imperfections, and specific energy demand while welding. Additionally, measurements of hardness and tensile tests illustrate usage property and constraint of both fiber laser concepts in micro welding.