Porosity analysis of additive manufactured parts using CAQ technology

materials Article Porosity Analysis of Additive Manufactured Parts Using CAQ Technology Peter Pokorný1,* , Štefan Václav 1, Jana Petru 2and Michaela Kritikos 1   Citation: Pokorný, P.; Václav, Š.; Petru, J.; Kritikos, M. Porosity Analysis of Additive Manufactured Parts Using CAQ Technology. Materials 2021,14, 1142. https:// doi.org/10.3390/ma14051142 Academic Editor: Tuhin Mukherjee Received: 29 January 2021 Accepted: 24 February 2021 Published: 28 February 2021 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Copyright: © 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). 1Faculty of Materials Science and Technology in Trnava, Institute of Production Technologies, Slovak University of Technology in Bratislava, 917 24 Trnava, Slovakia; [email protected] (Š.V.); [email protected] (M.K.) 2Faculty of Mechanical Engineering, VŠB—Technical University of Ostrava, 70800 Ostrava, Czech Republic; [email protected] *Correspondence: peter[email protected] Abstract: Components produced by additive technology are implemented in various spheres of industry, such as automotive or aerospace. This manufacturing process can lead to making highly optimized parts. There is not enough information about the quality of the parts produced by additive technologies, especially those made from metal powder. The research in this article deals with the porosity of components produced by additive technologies. The components used for the research were manufactured by the selective laser melting (SLM) method. The shape of these components is the same as the shape used for the tensile test. The investigated parts were printed with orientation in two directions, Z and XZ with respect to the machine platform. The printing strategy was “stripe”. The material used for printing of the parts was SS 316L-0407. The printing parameters were laser power of 200 W, scanning speed of 650 mm/s, and the thickness of the layer was 50 µ m. A non-destructive method was used for the components’ porosity evaluation. The scanning was performed by CT machine METROTOM 1500. The radiation parameters used for getting 3D scans were voltage 180 kV, current 900 µ A, detector resolution 1024 × 1024 px, voxel size 119.43 µ m, number of projections 1050, and integration time 2000 ms. This entire measurement process responds to the computer aided quality (CAQ) technology. VG studio MAX 3.0 software was used to evaluate the obtained data. The porosity of the parts with Z and XZ orientation was also evaluated for parts’ thicknesses of 1, 2, and 3 mm, respectively. It has been proven by this experimental investigation that the printing direction of the part in the additive manufacturing process under question affects its porosity. Keywords: porosity; additive technology; SLM; computer tomography 1. Introduction Extensive funds are invested in additive technologies. Large corporations are building laboratories focused on research and the application of additive technologies. For example, it is possible to cite the Centre for Additive Technology [ 1 ]. Components made with additive technologies are also implemented in the automotive and aerospace industries; for example, the use of additive manufacturing to manufacture fuel nozzles [ 2 ]. Additive technologies for the production of metal components use various metal powders. Bajaj et al. dealt with steels used in the additive manufacturing process in their experimental investigation. The article compares some mechanical properties of components produced by additive technology and conventional technology. It was proven that some properties (hardness, corrosion resistance) are better for components made with additive technologies. Some properties, such as ductility or fatigue strength, are worse for components made by additive technologies in comparison to conventionally produced steel parts [ 3 ]. One of the kinds of steel powders used for additive production is 316L. Similarly, other authors have researched and described the change in the mechanical properties and change of the structure of parts produced by the selective laser melting (SLM) method [ 4 ]. Through the analysis Materials 2021,14, 1142. https://doi.org/10.3390/ma14051142 https://www.mdpi.com/journal/materials Materials 2021,14, 1142 2 of 14 of mechanical properties, these authors were able to determine the direction in which these properties were changing. Additionally, anisotropic properties of steel were studied in different papers [ 5 ]. These papers specifically examined stainless steel. The authors investigated the properties of components produced by additive technology that were oriented at different angles during production. They found out that components made at an angle of 45 ◦ had the highest tensile strength. Research has shown that the angle of orientation of a part during its production and the direction of its fibres are influenced by the tensile characteristics. In a similar way, the heat treatment, mechanical, and microstructural properties of stainless steel were discussed in investigations by the authors in [ 6 – 8 ]. On the other hand, the parameters of the production process in the production of components by additive technology are important. These include, for example, distance of points and time of exposure. The combination of these parameters has also an influenced the porosity, component surface, microstructure of the material, density, and hardness. The parameters of the sintering process of the powders were investigated [ 9 ]. These authors found that, with the increase of the laser energy, the temperature at the sintering site increases and thus the melt fills the voids, leading to a porosity reduction in the component. Another important parameter that affects the properties of the component is the scanning strategy used in the producing process, which in this case, is basically a computer aided manufacturing (CAM) strategy. CAM strategies are also used in conventional machining methods; for example, in the milling process. One article [ 10 ] shows the influence of milling strategies on surface accuracy. In this work, a part with simple shapes was modelled. Three finishing strategies (optimized constant Z, spiral finishing, and offset finishing) were applied to these shapes. Afterwards, the measuring of machined cylindrical surfaces was performed by the optical 3D scanner and then by Contura G2. It is clear from the results that the optimized constant Z milling strategy is the most suitable for a simple cylindrical surface. The smallest deviations were recorded in both types of measurements for this strategy. It is actually a movement along the shape of the part, which removes the material during machining and adds material during scanning in additive production. Similarly, authors [ 11 , 12 ] investigated the influence of scanning strategy parameters on residual stress by SLM technology and the impact of process on the final component properties. Three scanning strategies were used (chessboard, stripes, and the meander strategy). A high density of sintered material of up to 99.695% was found. The effect of the laser power on the residual stress was also proven. In terms of the grain structure, this was observed and detailed in the article [ 13 ], where the influence of two scanning strategies on the grain structure in the material was studied. The authors used two scanning strategies (island and back and forth). The study showed that a more homogeneous structure can only be achieved by changing the scanning strategy. Here, scanning strategies were applied to a simple sample shape (block). The structure may develop differently on a sample with more complex shape. Mechanical properties of AISI 316 stainless steel engaging different orientation of parts were presented in [ 14 ]. In this case, the samples were made with different orientations with respect to the machine platform. The sintering parameters were constant for all samples, while the orientation was the only parameter changing. Measurements have shown that some mechanical properties (such as strength) of steel produced by additive technology are better than those of steel produced by rolling. Similarly, these samples showed anisotropy of properties with respect to their orientation during production. Also, an important property of components is their porosity. The article [ 15 ] investigates porosity and microhardness of 316L. When examining the porosity, the areas on the samples with defects were evaluated. One sample was examined by the non-destructive X-ray computer tomography (XCT) method. The other samples were subjected to metallographic examination. A high sample density of more than 99% and a low porosity of about 0.82% were investigated. The pores were not evenly distributed. The samples had higher microhardness than the parts made by molding. Still, in this regard, the authors in [ 16 ] investigated density and porosity of sintered steel. The article analyzed particle size, particle shape, temperature of sintering, and time of sintering. These parameters affect the properties of the parts. They determined Materials 2021,14, 1142 3 of 14 the relationships between the parameters of the sintering process and the properties of the parts. The authors [ 17 ] described the possibility of using computer tomography (CT) to evaluate the properties of parts produced by additive technology. They analyzed the use of CT from several perspectives (defects, dimensions, density, and roughness). Based on an extensive analysis of the use of CT to measure the properties of parts produced by additive technology, they made suggestions for evaluating the relationship between the production of parts and their mechanical behaviour. In addition, they concluded that international standards for the use of CT for printing technology needed to be set; that it was necessary to specify a reference element for CT calibration; and that due to the high cost of CT machines, it was necessary to consider using other cheaper measurement methods as well to establish standards for examining the surface of parts via CT; and, thus, developing a software tool to simulate the CT process would be of great aid. In the article [ 18 ], the authors used CT to investigate the properties of parts. Samples were made by P µ LSE stereolithography. They used CT to examine surface defects and lattice defects. Thus, they predicted the behaviour of mechanical properties and defects in the lattice. They performed shearing experiments. They summarized the findings of the experimental investigation in several points, concluding that geometry defects were related to the direction of the part building, and that geometry defects affected the development of defects in the material grid itself. On the other hand, the results of their finite element simulations showed the influence of geometry on the formation of defects in the material lattice. In this paper, we focused on the research of porosity in components made by additive technology, specifically, SLM technology. The motivation for this research was the study of materials and scientific publications on the porosity of materials produced by SLM. These studies have shown that porosity needs to be deeper examined given that it can significantly affect the mechanical properties of parts. The study of porosity and other properties of parts made by 3D printing must lead to quality products that will be produced in a shorter time. In our study, the designed parts were manufactured at constant 3D printing parameters, i.e., the sintering conditions were not changing. The influence of the parameters of the sintering process on the porosity was not observed. The shape of these components was the same as the shape used for the tensile test. Samples were manufactured with three different thicknesses (1, 2, 3 mm). The samples were printed in different directions with respect to the machine platform, specifically, in the XZ and Z directions. The CT measurement method was used to measure the porosity of components manufactured by the SLM additive technology. Porosity data were evaluated for individual part thicknesses and for individual part orientations in the machine. The main goal of the study was to determine how the orientation of the part during its production affects the porosity. 2. Materials and Methods The 316L-0407 powder from Renishaw was used in this study. This is an austenitic stainless steel. The applications of this steel are in the plastic industry and die casting molds, dies for extrusion, instruments for surgery, and parts for the navy. The material composition is in Table 1[19]. Table 1. Chemical components of the 316L-0407 powder used for experiments. Element Fe Cr Ni Mo Mn Si P C S Mass (%) Balance 16–18 10–14 2–3 ≤2≤1≤ 0.045 ≤0.03 ≤0.03 All parts were produced by using the Renishaw AM400 (Wotton-under-Edge, UK) machine. The parameters of the process used in this article were power of laser 200 W, speed of scanning 650 mm/s, and thickness of layer 50 µ m. The investigated parts were printed with orientation in two directions—Z and XZ. Material thicknesses of printed parts were 1, 2, 3 mm. (Figure 1). Materials 2021,14, 1142 4 of 14 Materials 2021, 14, x 4 of 14 printed with orientation in two directions—Z and XZ. Material thicknesses of printed parts were 1, 2, 3 mm. (Figure 1). (a) (b) Figure 1. Investigated parts printed with different orientation with respect to the machine platform (a) Part orientation in Z direction; (b) Part orientation in XZ direction. Different scanning strategies were used to produce components by the SLM method. By applying these strategies, we obtained a finer grain structure [20,21]. In this way, it is possible to produce components with thin walls [22]. Parts for our experiment were made using a “strip” strategy of scanning (Figure 2). Figure 2. Strip scanning strategy used to build our components by the selective laser melting (SLM) method. A non-destructive method for evaluation of the components’ porosity was used in this study. This method is suitable for measuring dimensions, but also for measuring the structures of materials. Goméz et. al. compared measurements by CT techniques and the coordinate measuring machine (CMM). They also discussed standards for estimating measurement uncertainty [23]. The case studies [24,25] compared the CT method and measurement techniques with classical metrology implemented on CMM. They pointed out the advantages of using CT measurement methods. Measurement strategies using CT were investigated and evaluated. The result was evidence of the suitability of CT measurement for production processes, dimensional measurement, and structural control (external, internal). Experimental investigation was performed on the device METROTOM 1500 from Zeiss (Oberkochen, Germany), using computed tomography. This device consists of these main parts: X-ray tube, rotational table, and detector, which is used for capturing two dimensional images. Software used for scanning and getting data was METROTOM OS 2.8. The X-ray set ups were made according to producer recommendations and skills of the operator: • Voltage: 180 kV • Current: 900 µA • Resolution: 1024 × 1024 px • Voxel size: 119.43 µm • Nr of projections: 1050 Figure 1. Investigated parts printed with different orientation with respect to the machine platform ( a ) Part orientation in Z direction; (b) Part orientation in XZ direction. Different scanning strategies were used to produce components by the SLM method. By applying these strategies, we obtained a finer grain structure [ 20 , 21 ]. In this way, it is possible to produce components with thin walls [ 22 ]. Parts for our experiment were made using a “strip” strategy of scanning (Figure 2). Materials 2021, 14, x 4 of 14 printed with orientation in two directions—Z and XZ. Material thicknesses of printed parts were 1, 2, 3 mm. (Figure 1). (a) (b) Figure 1. Investigated parts printed with different orientation with respect to the machine platform (a) Part orientation in Z direction; (b) Part orientation in XZ direction. Different scanning strategies were used to produce components by the SLM method. By applying these strategies, we obtained a finer grain structure [20,21]. In this way, it is possible to produce components with thin walls [22]. Parts for our experiment were made using a “strip” strategy of scanning (Figure 2). Figure 2. Strip scanning strategy used to build our components by the selective laser melting (SLM) method. A non-destructive method for evaluation of the components’ porosity was used in this study. This method is suitable for measuring dimensions, but also for measuring the structures of materials. Goméz et. al. compared measurements by CT techniques and the coordinate measuring machine (CMM). They also discussed standards for estimating measurement uncertainty [23]. The case studies [24,25] compared the CT method and measurement techniques with classical metrology implemented on CMM. They pointed out the advantages of using CT measurement methods. Measurement strategies using CT were investigated and evaluated. The result was evidence of the suitability of CT measurement for production processes, dimensional measurement, and structural control (external, internal). Experimental investigation was performed on the device METROTOM 1500 from Zeiss (Oberkochen, Germany), using computed tomography. This device consists of these main parts: X-ray tube, rotational table, and detector, which is used for capturing two dimensional images. Software used for scanning and getting data was METROTOM OS 2.8. The X-ray set ups were made according to producer recommendations and skills of the operator: • Voltage: 180 kV • Current: 900 µA • Resolution: 1024 × 1024 px • Voxel size: 119.43 µm • Nr of projections: 1050 Figure 2. Strip scanning strategy used to build our components by the selective laser melting (SLM) method. A non-destructive method for evaluation of the components’ porosity was used in this study. This method is suitable for measuring dimensions, but also for measuring the structures of materials. Goméz et al. compared measurements by CT techniques and the coordinate measuring machine (CMM). They also discussed standards for estimating measurement uncertainty [ 23 ]. The case studies [ 24 , 25 ] compared the CT method and measurement techniques with classical metrology implemented on CMM. They pointed out the advantages of using CT measurement methods. Measurement strategies using CT were investigated and evaluated. The result was evidence of the suitability of CT measurement for production processes, dimensional measurement, and structural control (external, internal). Experimental investigation was performed on the device METROTOM 1500 from Zeiss (Oberkochen, Germany), using computed tomography. This device consists of these main parts: X-ray tube, rotational table, and detector, which is used for capturing two dimensional images. Software used for scanning and getting data was METROTOM OS 2.8. The X-ray set ups were made according to producer recommendations and skills of the operator: •Voltage: 180 kV •Current: 900 µA •Resolution: 1024 ×1024 px •Voxel size: 119.43 µm •Nr of projections: 1050 •Integration time: 2000 ms A cupper filter with thickness of 3 mm was used. The distance between the X-ray source and the scanning part was 450 mm. Materials 2021,14, 1142 5 of 14 Three dimensional models were evaluated in the VGStudio MAX 3.0 software (Volume Graphics, Heidelberg, Germany) after reconstruction. The first step was surface determination for recognition of the shape of the part. After that, 2 × compatibility porosity analysis was used. Its application shows pores scanned in each part. The principle of non-destructive measurement by CT is shown in (Figure 3). The position of the parts located in the computed tomography device is shown in (Figure 4). Materials 2021, 14, x 5 of 14 • Integration time: 2000 ms A cupper filter with thickness of 3 mm was used. The distance between the X-ray source and the scanning part was 450 mm. Three dimensional models were evaluated in the VGStudio MAX 3.0 software (Volume Graphics, Heidelberg, Germany) after reconstruction. The first step was surface determination for recognition of the shape of the part. After that, 2 × compatibility porosity analysis was used. Its application shows pores scanned in each part. The principle of nondestructive measurement by CT is shown in (Figure 3). The position of the parts located in the computed tomography device is shown in (Figure 4). Figure 3. Principle of measurement by industrial computer tomography (CT). (a) (b) (c) Figure 4. The position of the parts in the computer tomography device (a) View of the source of the X-rays, (b) View of the X-ray detector, (c) View of the experimental parts. Figure 3. Principle of measurement by industrial computer tomography (CT). Materials 2021, 14, x 5 of 14 • Integration time: 2000 ms A cupper filter with thickness of 3 mm was used. The distance between the X-ray source and the scanning part was 450 mm. Three dimensional models were evaluated in the VGStudio MAX 3.0 software (Volume Graphics, Heidelberg, Germany) after reconstruction. The first step was surface determination for recognition of the shape of the part. After that, 2 × compatibility porosity analysis was used. Its application shows pores scanned in each part. The principle of nondestructive measurement by CT is shown in (Figure 3). The position of the parts located in the computed tomography device is shown in (Figure 4). Figure 3. Principle of measurement by industrial computer tomography (CT). (a) (b) (c) Figure 4. The position of the parts in the computer tomography device (a) View of the source of the X-rays, (b) View of the X-ray detector, (c) View of the experimental parts. Figure 4. The position of the parts in the computer tomography device ( a ) View of the source of the X-rays, (b) View of the X-ray detector, (c) View of the experimental parts. 3. Results The first step was surface determination for recognition of the shape of the part. After that, 2 × compatibility porosity analysis was used. Its application shows pores scanned Materials 2021,14, 1142 6 of 14 in each part. Figure 5shows the pores in the part, which had a thickness of 1 mm and an orientation of layers in the Z direction. Materials 2021, 14, x 6 of 14 3. Results The first step was surface determination for recognition of the shape of the part. After that, 2 × compatibility porosity analysis was used. Its application shows pores scanned in each part. Figure 5 shows the pores in the part, which had a thickness of 1 mm and an orientation of layers in the Z direction. Figure 5. Pores detected in a part, which had a thickness of 1 mm oriented in Z. Identification of defects at selected locations in the sample, which had a thickness of 1 mm and was oriented in the Z direction, is shown in Figure 6. Figure 6. The biggest defects in the sample, which had a thickness of 1 mm and was oriented in Z. Figure 7 shows the statistics of evaluated values of material volume, defect volume, and defect volume ratio for a sample, which had a thickness of 1 mm and was Z oriented. Figure 7. Evaluated values for a sample with a thickness of 1 mm, which is oriented in Z. Figure 5. Pores detected in a part, which had a thickness of 1 mm oriented in Z. Identification of defects at selected locations in the sample, which had a thickness of 1 mm and was oriented in the Z direction, is shown in Figure 6. Materials 2021, 14, x 6 of 14 3. Results The first step was surface determination for recognition of the shape of the part. After that, 2 × compatibility porosity analysis was used. Its application shows pores scanned in each part. Figure 5 shows the pores in the part, which had a thickness of 1 mm and an orientation of layers in the Z direction. Figure 5. Pores detected in a part, which had a thickness of 1 mm oriented in Z. Identification of defects at selected locations in the sample, which had a thickness of 1 mm and was oriented in the Z direction, is shown in Figure 6. Figure 6. The biggest defects in the sample, which had a thickness of 1 mm and was oriented in Z. Figure 7 shows the statistics of evaluated values of material volume, defect volume, and defect volume ratio for a sample, which had a thickness of 1 mm and was Z oriented. Figure 7. Evaluated values for a sample with a thickness of 1 mm, which is oriented in Z. Figure 6. The biggest defects in the sample, which had a thickness of 1 mm and was oriented in Z. Figure 7shows the statistics of evaluated values of material volume, defect volume, and defect volume ratio for a sample, which had a thickness of 1 mm and was Z oriented. Materials 2021, 14, x 6 of 14 3. Results The first step was surface determination for recognition of the shape of the part. After that, 2 × compatibility porosity analysis was used. Its application shows pores scanned in each part. Figure 5 shows the pores in the part, which had a thickness of 1 mm and an orientation of layers in the Z direction. Figure 5. Pores detected in a part, which had a thickness of 1 mm oriented in Z. Identification of defects at selected locations in the sample, which had a thickness of 1 mm and was oriented in the Z direction, is shown in Figure 6. Figure 6. The biggest defects in the sample, which had a thickness of 1 mm and was oriented in Z. Figure 7 shows the statistics of evaluated values of material volume, defect volume, and defect volume ratio for a sample, which had a thickness of 1 mm and was Z oriented. Figure 7. Evaluated values for a sample with a thickness of 1 mm, which is oriented in Z. Figure 7. Evaluated values for a sample with a thickness of 1 mm, which is oriented in Z. Materials 2021,14, 1142 7 of 14 Figure 8shows the pores in the 1 mm thick sample with an orientation of layers in the XZ direction. Materials 2021, 14, x 7 of 14 Figure 8 shows the pores in the 1 mm thick sample with an orientation of layers in the XZ direction. Figure 8. Defects detected in the sample with thickness of 1 mm printed in XZ directions. The identification of the biggest defects at specific locations of the sample with 1 mm thickness, which was oriented in the XZ direction, is shown in Figure 9. Figure 9. Specific defects evaluated in the sample, which had 1 mm thickness and was oriented XZ. Figure 10 shows the measured values of material volume, defect volume, and defect volume ratio for a sample, which had 1 mm thickness and was oriented XZ. Figure 10. Measured values for a sample with a thickness of 1 mm and oriented XZ. Figure 8. Defects detected in the sample with thickness of 1 mm printed in XZ directions. The identification of the biggest defects at specific locations of the sample with 1 mm thickness, which was oriented in the XZ direction, is shown in Figure 9. Materials 2021, 14, x 7 of 14 Figure 8 shows the pores in the 1 mm thick sample with an orientation of layers in the XZ direction. Figure 8. Defects detected in the sample with thickness of 1 mm printed in XZ directions. The identification of the biggest defects at specific locations of the sample with 1 mm thickness, which was oriented in the XZ direction, is shown in Figure 9. Figure 9. Specific defects evaluated in the sample, which had 1 mm thickness and was oriented XZ. Figure 10 shows the measured values of material volume, defect volume, and defect volume ratio for a sample, which had 1 mm thickness and was oriented XZ. Figure 10. Measured values for a sample with a thickness of 1 mm and oriented XZ. Figure 9. Specific defects evaluated in the sample, which had 1 mm thickness and was oriented XZ. Figure 10 shows the measured values of material volume, defect volume, and defect volume ratio for a sample, which had 1 mm thickness and was oriented XZ. Materials 2021, 14, x 7 of 14 Figure 8 shows the pores in the 1 mm thick sample with an orientation of layers in the XZ direction. Figure 8. Defects detected in the sample with thickness of 1 mm printed in XZ directions. The identification of the biggest defects at specific locations of the sample with 1 mm thickness, which was oriented in the XZ direction, is shown in Figure 9. Figure 9. Specific defects evaluated in the sample, which had 1 mm thickness and was oriented XZ. Figure 10 shows the measured values of material volume, defect volume, and defect volume ratio for a sample, which had 1 mm thickness and was oriented XZ. Figure 10. Measured values for a sample with a thickness of 1 mm and oriented XZ. Figure 10. Measured values for a sample with a thickness of 1 mm and oriented XZ. Materials 2021,14, 1142 8 of 14 Parts with 2 and 3 mm thickness with orientation in the Z and X directions were evaluated in an identical way. The identification of defects at specific locations of the sample with 2 mm thickness, which was oriented in the Z direction, is shown in Figure 11. Figure 12 shows samples printed in the XZ direction. Materials 2021, 14, x 8 of 14 Parts with 2 and 3 mm thickness with orientation in the Z and X directions were evaluated in an identical way. The identification of defects at specific locations of the sample with 2 mm thickness, which was oriented in the Z direction, is shown in Figure 11. Figure 12 shows samples printed in the XZ direction. Figure 11. Specific defects on a sample with 2 mm thickness, which was oriented in the Z direction. Figure 12. Specific defects on a sample with 2 mm thickness, which was oriented XZ. Figure 13 shows the measured values of material volume, defect volume, and defect volume ratio for the sample with thickness of 2 mm, which was oriented in the Z direction. The measured values for the sample oriented XZ are shown in Figure 14. Figure 13. Measured values for a sample with 2 mm thickness, which is oriented in Z. Figure 11. Specific defects on a sample with 2 mm thickness, which was oriented in the Z direction. Materials 2021, 14, x 8 of 14 Parts with 2 and 3 mm thickness with orientation in the Z and X directions were evaluated in an identical way. The identification of defects at specific locations of the sample with 2 mm thickness, which was oriented in the Z direction, is shown in Figure 11. Figure 12 shows samples printed in the XZ direction. Figure 11. Specific defects on a sample with 2 mm thickness, which was oriented in the Z direction. Figure 12. Specific defects on a sample with 2 mm thickness, which was oriented XZ. Figure 13 shows the measured values of material volume, defect volume, and defect volume ratio for the sample with thickness of 2 mm, which was oriented in the Z direction. The measured values for the sample oriented XZ are shown in Figure 14. Figure 13. Measured values for a sample with 2 mm thickness, which is oriented in Z. Figure 12. Specific defects on a sample with 2 mm thickness, which was oriented XZ. Figure 13 shows the measured values of material volume, defect volume, and defect volume ratio for the sample with thickness of 2 mm, which was oriented in the Z direction. The measured values for the sample oriented XZ are shown in Figure 14. Materials 2021, 14, x 8 of 14 Parts with 2 and 3 mm thickness with orientation in the Z and X directions were evaluated in an identical way. The identification of defects at specific locations of the sample with 2 mm thickness, which was oriented in the Z direction, is shown in Figure 11. Figure 12 shows samples printed in the XZ direction. Figure 11. Specific defects on a sample with 2 mm thickness, which was oriented in the Z direction. Figure 12. Specific defects on a sample with 2 mm thickness, which was oriented XZ. Figure 13 shows the measured values of material volume, defect volume, and defect volume ratio for the sample with thickness of 2 mm, which was oriented in the Z direction. The measured values for the sample oriented XZ are shown in Figure 14. Figure 13. Measured values for a sample with 2 mm thickness, which is oriented in Z. Figure 13. Measured values for a sample with 2 mm thickness, which is oriented in Z. Materials 2021,14, 1142 9 of 14 Materials 2021, 14, x 9 of 14 Figure 14. Measured values for a sample with 2 mm thickness, which is oriented in XZ. The identification of defects at specific locations of the sample with 3 mm thickness, which was oriented in the Z direction, is shown in Figure 15. Figure 15. Specific defects in the sample with 3 mm thickness, which was oriented in Z. The identification of defects at specific locations of the sample with thickness of 3 mm, which was oriented in the XZ direction, is shown in Figure 16. Figure 16. Specific defects in the sample with thickness of 3 mm, which was oriented in XZ. Figure 17 shows the measured values of material volume, defect volume, and defect volume ratio for a sample with thickness of 3 mm, which was oriented in Z. Figure 18 shows the measured values of material volume, defect volume, and defect volume ratio for the sample with thickness of 3 mm, which was oriented in XZ. Figure 14. Measured values for a sample with 2 mm thickness, which is oriented in XZ. The identification of defects at specific locations of the sample with 3 mm thickness, which was oriented in the Z direction, is shown in Figure 15. Materials 2021, 14, x 9 of 14 Figure 14. Measured values for a sample with 2 mm thickness, which is oriented in XZ. The identification of defects at specific locations of the sample with 3 mm thickness, which was oriented in the Z direction, is shown in Figure 15. Figure 15. Specific defects in the sample with 3 mm thickness, which was oriented in Z. The identification of defects at specific locations of the sample with thickness of 3 mm, which was oriented in the XZ direction, is shown in Figure 16. Figure 16. Specific defects in the sample with thickness of 3 mm, which was oriented in XZ. Figure 17 shows the measured values of material volume, defect volume, and defect volume ratio for a sample with thickness of 3 mm, which was oriented in Z. Figure 18 shows the measured values of material volume, defect volume, and defect volume ratio for the sample with thickness of 3 mm, which was oriented in XZ. Figure 15. Specific defects in the sample with 3 mm thickness, which was oriented in Z. The identification of defects at specific locations of the sample with thickness of 3 mm, which was oriented in the XZ direction, is shown in Figure 16. Materials 2021, 14, x 9 of 14 Figure 14. Measured values for a sample with 2 mm thickness, which is oriented in XZ. The identification of defects at specific locations of the sample with 3 mm thickness, which was oriented in the Z direction, is shown in Figure 15. Figure 15. Specific defects in the sample with 3 mm thickness, which was oriented in Z. The identification of defects at specific locations of the sample with thickness of 3 mm, which was oriented in the XZ direction, is shown in Figure 16. Figure 16. Specific defects in the sample with thickness of 3 mm, which was oriented in XZ. Figure 17 shows the measured values of material volume, defect volume, and defect volume ratio for a sample with thickness of 3 mm, which was oriented in Z. Figure 18 shows the measured values of material volume, defect volume, and defect volume ratio for the sample with thickness of 3 mm, which was oriented in XZ. Figure 16. Specific defects in the sample with thickness of 3 mm, which was oriented in XZ. Figure 17 shows the measured values of material volume, defect volume, and defect volume ratio for a sample with thickness of 3 mm, which was oriented in Z. Figure 18 shows the measured values of material volume, defect volume, and defect volume ratio for the sample with thickness of 3 mm, which was oriented in XZ.