9th Conference on Industrial Computed Tomography, Padova, Italy (iCT 2019) 1 Optimization of surface determination to improve the accuracy of detecting unfused powder in AM Aluminium component Ahmed Tawfik 1 , Liam Blunt 1 , Christopher Dawson 1 , Radu Racasan 1 , Desi Bacheva 2 , Paul Bills 1 EPSRC Future Advanced Metrology Hub, University of Huddersfield 1 , Huddersfield, United Kingdom, Ahmed.Tawfik@hud.ac.uk HiETA Technologies Ltd 2 Bristol & Bath Science Park Dirac Crescent Emersons Green Bristol BS16 7FR desibacheva@hieta.biz Abstract Additive manufacturing (AM) is quickly being recognized as a core technology for producing complex and customized components, so the need for well understood non-destructive testing is more urgent than ever. The mechanical properties of cast components are well studied and non-destructive testing is well established by various methods like XCT and ultrasound. On the other hand, there are big challenges for NDT with regard to additive manufactured components as the pores are different in nature from those found in cast alternatives. In additive manufactured components, the pores could be hollow, filled with partially fused powder or unfused powder. Furthermore, porosity could be due lack of fusion of un-melted powder (low laser energy) or balling up effect (too high laser energy). There is also the possibility of unfused powder within the internal architecture of complex components. In such cases XCT becomes an essential detection tool. This paper presents the design of an Aluminum (AlSi10Mg) AM artefact / sample with built-in unfused and semi fused powder features. Several defects with different shapes and dimensions were created. Two 1mm cylinder defects were placed inside an 8mm aluminum cylinder artefact. The first defect was located 200μm from the outside envelope of the surface and the second defect was located centrally 1mm from the top surface of the artefact. The built-in defects were used as markers to identify the determined powder grey value. A Nikon XTH 225 (Nikon Metrology, Tring) industrial XCT was used to analyze the pores/ defects’ location and volume. This threshold was utili zed to ascertain the optimum ISO value for surface determination. Data processing, surface determination process and defect analysis was carried out using VG Studio Max 3.1 (Volume Graphics, Heidelberg).The artefact was then sectioned to confirm the actual location and dimensions of the designed defects using an Alicona G4 (Alicona, Graz) focus variation instrument.. The results of the scans were determined using two different surface determination strategies. The results obtained from each of the defect analysis were compared to the designed value and the focus variation. The focus of the study is on providing best practice for selecting inspection parameters, optimizing ISO value for porosity detection and identifying unfused and semi fused powder in AM SLM component. Keywords: Additive manufacturing, Surface determination, Porosity analysis, Unfused powder, Non-destructive testing. AlSi10Mg Introduction Additive manufacturing (AM) is the process in which powder or wire is sintered to build parts layer by layer. AM is a relatively new approach to manufacturing and offers great potential over subtractive machining, in terms of weight reduction, design optimization and the creation of complex components with internal and external features that would be impossible with conventional machining [1-2]. The possible weight savings through use of AM design optimization will help to achieve carbon footprint reduction by reducing fuel consumption in aerospace and automotive applications. Furthermore, the amount of material waste in the AM process can be much lower than in subtractive manufacturing [3] especially when considering powder recycling. Several metallic materials are currently used in AM, ranging from Inconel to Aluminum [4-7]. At the moment one of the main reasons stopping AM from becoming more widely used in many industries is inconsistent fatigue performance. This issue is due to the existence of internal defects as a by product of the manufacturing process. These internal defects can reduce the fatigue life of mechanical components dramatically [8]. Also, it has been found that subsurface porosity can lead to crack initiation hot spots which vastly decrease the fatigue life of any AM mechanical components [9-14]. X-ray computed tomography (XCT) is widely used for measuring and non-destructive testing of AM components, this is due to the difficulty in measuring complex outer and inner geometry using conventional measurement techniques normally through methods such as CMM which can be time consuming and still require a large amount of post processing to determine full geometries. Furthermore, the ability of AM to build internal structures within components and consequent possible existence of internal defects requires an inspection method that can acquire internal dimensions and volumes. While XCT looks promising with various different technologies available, one of the main obstacles that stops XCT from being accepted is the level of subjectivity within the process allied to a lack of verification; the only way to verify internal features is by sectioning the part thus the process becomes destructive, losing time and costs. The challenges in inspecting More info about this article: http://www.ndt.net/?id=23728