PSI - Issue 77

2

Y.Bakir et al./ Structural Integrity Procedia 00 (2026) 000–000

Y. Bakir et al. / Procedia Structural Integrity 77 (2026) 639–648

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Nomenclature AM

Additive Manufacturing

CT Computed Tomography CMOS Complementary Metal Oxide Semiconductor HAZ Heat Affected Zone LPBF Laser Powder Bed Fusion GV Grey Value SLM Selective Laser Melting TGM Temperature Gradient Mechanism

1. Introduction Additive manufacturing (AM) is the process of building parts from 3D data by combining materials usually where subtractive manufacturing refers to building parts by removing materials from a solid block of material [1] As a type of AM process, Laser Powder Bed Fusion (LPBF) refers to fashion by which parts are produced layer by layer from material powders, such as stainless steel, maraging steel, cobalt chromium, titanium alloys and many others[2]. Selective Laser Melting(SLM) is method of AM that utilizes a laser beam that applies energy on the area of a very fine spot size, this way laser is capable of melting certain metal powders. SLM will preferred term in this work. Metal powder is melted in a layer by layer fashion to produce parts. SLM offers near unlimited geometrical freedom for the parts built. While it has been used for prototyping for a long time, SLM technology has shown significant progress in recent years regarding machine construction, production speed, variety of materials used. This way, it has become a feasible manufacturing process for serial production. However, despite its evolution one of the main challenges keeping SLM from wider adaptation is quality assurance. X-ray computed tomography(CT) can be used for ensuring internal quality of the parts. The disadvantages of CT however are, its high cost, limited accuracy and the limitation of the size of the part that can be evaluated[3]. There are variety of data gathering devices, that can be utilized gathering data during SLM process. The use of photodiodes and cameras as data gathering tools will be the focus of this work. In addition, there are also different approaches of utilizing monitoring devices. There can be differences in the placement of monitoring tools, as well as in the area of focus during data gathering and also in the processing of the data gathered. Management of the heat applied during production is very important. Excess heat may cause deformations and cracks while insufficient heat applied may result in errors in the form of un-melted powder particles. Geometry of the parts produced by SLM process, directly dictate the way the applied heat energy is managed. Thin and long parts are prone to have poorer heat conduction characteristics. For this work, thin tensile testing samples are built and tested and data is gathered by an in situ monitoring system. The goal is to investigate any possible relations between the performance of the parts and the data gathered. This work builds upon results previously reported in the author’s Master’s thesis[4]. 2. Experimental Setup 2.1. Machine and Monitoring System Set-up For the production of the parts, an EOS M290 machine was used. This machine employs a 400W ytterbium laser to melt the metal powder. Ceramic blades were used for this work as method of hard recoating. This type of recoating is known to have tendency for process interruption in case of overheating or any process instabilities that might result in deformation of part.