Effect of wire feeder force control on laser metal deposition process using coaxial laser head

Laser based Direct Energy Deposition (DED), also called Laser Metal Deposition (LMD), is a process that is widely used for cladding and repair applications and increasingly for additive manufacturing processes [Chen Hong, Dongdong Gu, Donghua Dai, Andres Gasser, Andreas Weisheit, Ingomar Kelbassa, Minlin Zhong, and Reinhart Poprawe, Opt. Laser Technol. 54, 98–109 (2013)]. Its controlled energy input and its ability to control the dilution allow the use of less material and the production of thin and precise layers increasing productivity and reducing costs [Erwin Werner Teichmann, “Analysis of welding process variants aiming cladding with Inconel 625 of API X46 steel pipes,” Ph.D. thesis in Mechanical Engineering, Post-Graduation Program in Mechanical Engineering, Federal University of Santa Catarina—UFSC, Florianópolis, 2016, p. 213, see https://repositorio.ufsc.br/handle/123456789/17223 (accessed 12 May 2020); Thomas Schopphoven, Andres Gasser, and Gerhard Backes, “EHLA: Extreme high-speed laser material deposition,” Laser Tech. J. 14, 26–29 (2017)]. Associated with those characteristics is the ability to operate using both powder and wire additives. The last one presents a series of advantages, as lower price per kilogram, lower porosity on the deposited material, and lower health risks for users. The use of a coaxial wire feeding laser head allows an omnidirectional operation for the laser head, presenting a great advantage when compared to lateral feeding systems. For soldering applications, some suppliers offer wire feeding systems that allow one to control the force applied by the wire on the substrate. This system measures the contact between the wire and the bottom of the melt pool, enabling a bridge metal transfer mode. The bridge transfer mode is essential, since the surface tension plays the main influence and, on the other hand, gravity plays only a minor role in the metal transfer. The results of using a force control system with different settings and a comparison between samples produced with and without this control are discussed. The material for both, samples and wire, is the stainless steel 316L. To assist the analysis, high-speed videos, process data acquisition, and macrographs are made.