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Salminen A.,Lappeenranta University of Technology | Salminen A.,Machine Technology Center Turku Ltd.
Mechanika | Year: 2010

Laser welding is gaining new applications in various industries. Often the use of filler wire is not considered due to reputation of complicity. This study has, however gained almost no interest of research groups after millennium. The study showed that when certain rules are followed the filler wire feeding can be used and applied to industrial applications. The reflection of the laser beam from wire surface can be considerable, but I can be controlled due to its behavior according to the normal reflection laws. Even the fraction of beam reflecting from the wire surface can be utilized to the process. Source


Sokolov M.,Lappeenranta University of Technology | Salminen A.,Lappeenranta University of Technology | Salminen A.,Machine Technology Center Turku Ltd.
Physics Procedia | Year: 2014

The aim of this paper is to evaluate methods for improving laser beam welding efficiency, namely, obtaining increased penetration depth and enhanced weld quality without an increase in laser power or a decrease in welding speed. Increased efficiency can be realized with several techniques: butt joint edge surface modifications, preheating and modifications of ambient atmospheric conditions. Methods for laser beam welding process efficiency improvement are analysed and compared both separately and combined. Improvement in penetration depth or welding speed with similar penetration depth was noted for all the techniques studied. © 2014 The Authors. Published by Elsevier B.V. Source


Vanska M.,Lappeenranta University of Technology | Abt F.,University of Stuttgart | Weber R.,University of Stuttgart | Salminen A.,Lappeenranta University of Technology | And 2 more authors.
Physics Procedia | Year: 2013

The material and parameters like welding speed and laser beam parameters define the geometry of the keyhole. The keyhole geometry affects the weld geometry, such as width and depth, and in some cases it should be considered when selecting welding parameters. In-situ X-ray videography makes it possible to obtain time-and space resolved information about the keyhole geometry during the welding process. This paper describes the partial penetration laser welding experiments and shows the effects of a welding speed and a focal point position change onto some geometry values of the keyhole. Two different joint types were used, bead on plate to simulate a very good machined joint preparation and laser cut I-butt joint. © 2013 The Authors. Source


Purtonen T.,Lappeenranta University of Technology | Salminen A.,Lappeenranta University of Technology | Salminen A.,Machine Technology Center Turku Ltd.
Welding in the World | Year: 2014

Laser fusion cutting is a widely used process to cut stainless steel sheets and plates. In best cases, it provides such a good quality that it can be used instead of machining, e.g.; for manufacturing tube systems and components where accurately cut holes and sections are required. The flexibility of fiber lasers provides a fast and affordable way to accomplish these demands. This paper examines the effect of cutting position on fiber laser cutting of stainless steel. The tests consist of flat sheet bevel cutting, cutting of tubes in vertical and nonvertical positions and orbital cutting. The effect of different cutting positions and parameters to the final quality of the cut edge are studied. The parameters were, e.g.; material thickness, focal length, cutting speed, and laser power. The cutting tests were performed as high-pressure nitrogen cutting using a 5-kW multi-mode fiber laser. It was shown that the changed angle of incidence in the cutting direction had affected the cutting result. With a pushing cutting position, both the cutting quality and performance were improved. The results indicated clearly that orbital cutting is possible with the same parameters that are suitable for cutting in vertical position. © 2013 International Institute of Welding. Source


Islam M.,Lappeenranta University of Technology | Purtonen T.,Lappeenranta University of Technology | Piili H.,Lappeenranta University of Technology | Salminen A.,Lappeenranta University of Technology | And 2 more authors.
Physics Procedia | Year: 2013

Powder bed fusion is a laser additive manufacturing (LAM) technology which is used to manufacture parts layer-wise from powdered metallic materials. The technology has advanced vastly in the recent years and current systems can be used to manufacture functional parts for e.g. aerospace industry. The performance and accuracy of the systems have improved also, but certain difficulties in the powder fusion process are reducing the final quality of the parts. One of these is commonly known as the balling phenomenon. The aim of this study was to define some of the process characteristics in powder bed fusion by performing comparative studies with two different test setups. This was done by comparing measured temperature profiles and on-line photography of the process. The material used during the research was EOS PH1 stainless steel. Both of the test systems were equipped with 200 W single mode fiber lasers. The main result of the research was that some of the process instabilities are resulting from the energy input during the process. © 2013 The Authors. Source

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