Journal of Additive Manufacturing Technologies
The Journal of Additive Manufacturing Technologies is the peer-reviewed journal that reports research work on all aspects of additive manufacturing including additive manufacturing processes, design for additive manufacturing, modelling and simulation of additive manufacturing processes, post-processing in additive manufacturing, and applications of additive manufacturing. Papers relevant to these are all welcome. The journal aims to contribute additive manufacturing community by publishing high quality work that promote advancement of this manufacturing technology.
Non-destructive defect detection of LPBF-manufactured A205 aluminium alloy lattice structures
Engineering and design have been altered significantly by the production of metal lattice structures (MLS) utilizing additive manufacturing (AM), particularly laser powder bed fusion (LPBF). LPBF allows to produce such complex three-dimensional structures with a degree of complexity and accuracy which is not possible by conventional manufacturing, in particular regarding periodically repeated unit cells. However, despite its advantages, LPBF can cause defects, e.g. small internal porosities which in this case preferably can be observed with non-destructive inspection (NDI). Therefore, this study aims to validate the detectability of LPBF imperfections by exploring the impulse excitation technique (IET) as an NDI method for MLS and bulk samples produced by LPBF in the high-strength aluminium alloy A205 and including on-purpose manufactured defects. As a result of the measurements, the detection of selectively placed internal defects was successfully determined according to the differences in the resonant frequencies of defect-free and defected samples.
Copyright (c) 2025 Journal of Additive Manufacturing Technologies http://creativecommons.org/licenses/by/4.0
Functional island scanning strategy for powder bed fusion
Energy is transferred from the energy beam to the processed material during additive manufacturing (AM). The high energy input and uneven temperature distribution can result in a substantial temperature gradient, leading to significant thermal stress and warping deformation. One of the most influential factors in the material processing of additive manufacturing is the choice of scanning strategies. Therefore, optimizing the scanning strategy can help achieve a more even heat distribution across the part and reduce thermal distortion, which is crucial for producing high-quality SLM components. In this study, we developed a modified island scanning strategy and thermal management approach which is related to ordering the scanning sequence of islands, similar to the Traveling Salesman Problem (TSP) variant and it is also adapted for multiple laser cases. The introduction of modified island scan strategies aims to preserve the geometric integrity of the part, minimize distortion, and optimize the scanning process by considering the part’s geometric features, all while achieving the desired mechanical properties.
Localization of Acoustical Events in Laser Metal Deposition
Laser Metal Deposition (LMD) combines laser energy and powder material to create complex structures on existing components. It enables cost-effective production of multi-material compositions, like reinforcing metals with ceramic particles for enhanced wear resistance. However, dissimilar material characteristics can lead to defects, especially crack propagation and delamination. Efforts focus on optimizing process parameters and real-time monitoring to reduce the effort of mitigating defects. Assessing acoustic emissions aids in early defect detection and provides process stability insights. Besides of time- and frequency resolved information on the acoustical signals, precise defect localization is crucial, especially for manufacturing programs with multiple components on a substrate material. To instantly locate delamination defects, a multi-microphone array is proposed. This study also explores localization techniques, accuracy, and reliability. To investigate these, experiments on a test platform were used with simulated acoustical events that replicate known defect sounds.
Surface treatment effects on chemical milling performance of L-PBF produced Ti6Al4V ELI
Titanium is one of the most desirable engine materials in the cold sections of aero engines due to its low density and high strength. Titanium suffers from oxygen entrapment by the reason of heat treatment, high-temperature exposure and produced an oxygen-rich layer referred to as an alpha case. Laser Powder Bed Fusion (L-PBF) supports to production of the desired geometries that have high complexity. As a material fusion process, L-PBF causes parts to encounter the alpha case due to high temperature melting even though the process is done in an inert atmosphere. Since L-PBF produced parts that have high surface roughness value due to the semi-melted powders on the surfaces, it is difficult to remove the alpha case layer totally. In this study, Ti6Al4V ELI parts were produced by L-PBF and measured alpha case layer thickness before and after heat treatment and chemical milling. The three sandblasting (SB) parameters were used to facilitate a chemical attack on the parts surface before chemical milling processes. This study demonstrated that the SB process enhanced the chemical milling performance of L-PBF produced samples and the alpha case layer was successfully removed.
Copyright (c) 2022 Journal of Additive Manufacturing Technologies http://creativecommons.org/licenses/by/4.0
On the mechanical behavior and microstructural characterization of wire + arc additive manufacturing of Mn-Si based steel alloy (ER70S-6)
Wire + Arc Additive Manufacturing (WAAM) is relatively a novel manufacturing technology which uses metallic wire as the feedstock material and normal arc as the heat source to build up large scale near-net-shape parts. This process has attracted the attention of many industries such as aerospace, defense and automotive due to its ability to produce very near-net-shape components without complex tooling and molds offers potential for significant cost and lead time reductions. In this paper, the mechanical and metallurgical properties of the WAAM ER70S-6 are studied during tension loading as well as microhardness testing and its behavior is correlated with microstructural observations. The microstructure of WAAM ER70S-6 is assessed by optical microscopy (OM). The results show that the selected parameters for deposition of ER70S-6, leads to an isotropic mechanical behavior during tension loading. The microhardness level is not changing in different regions of WAAM-fabricated ER70S-6, confirming presence of relatively homogenous microstructure.
Combination of peridynamics and genetic algorithm based topology optimization methods for AM-friendly designs
Topology optimization (TO) is a practical tool to generate light-weighted engineering structures for various manufacturing industries. However, manufacturing constraints and surface smoothing are still considerable challenges for TO algorithms. Existing TO frameworks utilize mechanical analysis approaches that discretize the whole domain with elements or particles. Therefore, obtained geometries from TO have been criticized for their complex shapes. In this study, we propose a coupled framework to generate AM-friendly designs which result in less support structure and higher surface quality. For this purpose, the generative topology optimization method (GTO), which uses genetic algorithm to search for the best alternative set of geometry within all the possible topology results, is coupled with the peridynamics topology optimization (PD-TO) method to evolve the PD-TO results into AM-friendly shapes. The PD-TO discretizes the problem domain using equally spaced particles during the TO process. Hence, PD-TO generates a point cloud file with relevant artificial material density values in the final state. Then, the GTO method utilizes the point cloud and material densities as an input file to achieve better final geometry. AM-friendly designs achieved from GTO are compared with the initial results obtained from PD-TO to demonstrate the efficiency and capability of the proposed method.
Copyright (c) 2023 Journal of Additive Manufacturing Technologies http://creativecommons.org/licenses/by/4.0
Electromagnetic Characterization of 3D printed Metamaterial Absorber with Conductive Paint
In this study, electromagnetic characterization of 3D printed metamaterials manufactured by using conductive paint is carried out in terms of their absorption behavior. The samples have been prepared in sizes to fit waveguide setup in the frequency range of 12-18 GHz. 3D printing technique was used to prepare the substrate of the design while conductive paint and copper tape were used for the conductive parts of the structure including the metamaterial resonator and the ground plane. For electromagnetic characterization of the design, different thickness of substrate layers, various raster orientation (0°, ±45° and ±90°), different infill densities have been simulated and experimentally tested in terms of their effects on absorption behavior. In addition, conductivity of the paint was improved by adjusting its formulation and the resulting absorption behaviors have been compared with copper tape using the same metamaterial dimensions. Using 3D printing technology along with conductive paint rather than solid conductors in manufacturing electromagnetic absorbers will provide the possibility of producing flexible and non-planar electromagnetic absorber structures in desired frequency ranges. The design can be easily adopted to different frequencies and this technique can be used to design wideband metamaterial absorbers using 3D layered structures.
Copyright (c) 2023 Journal of Additive Manufacturing Technologies https://creativecommons.org/licenses/by/4.0/
Laser weldability of laser powder bed fused AlSi7Mg0.6
Laser Powder Bed Fusion (LPBF) allows to manufacture components with lightweight and near net shape suited to aerospace and aviation applications employing Al-alloys. The process is highly suited to one-of-a-kind or small batch production of small to medium sized parts. As the maturity of the process and its end-users increase, the demand for larger components becomes more relevant. The increase of part size by increasing the size of the LPBF machine inevitably increases the cost and the complexity of the employed system. Moreover, using multiple lasers in a large powder bed to produce larger parts may bring residual stresses, part deformation and a higher chance of process failure. In the light of these, the use of joining operations, in particular welding, appears as a suitable option for the production of large components via LPBF. Indeed, the process lends itself well to also producing dedicated joint edge preparations, thickness and section variation within the location of the welded joint. Amongst different processes, laser welding stands out as a viable option as it can provide narrower weld seam and heat affected zone, produce less deformation on the parts and be automated with cartesian or robotic manipulators. This work discusses the influence of different laser welding strategies on the LPBF produced AlSi7Mg0.6.
Peridynamic investigation of surface cracks in optimality criterion-based topology optimization for additive manufacturing
Topology optimization (TO) is extensively used for reducing the weight of engineering parts that require higher performance in aerospace, automotive, and defense industries. Additive manufacturing (AM), a practical layer-by-layer material deposition process, is commonly employed to fabricate geometrically complex designs obtained from TO. However, AM processes may result in manufacturing-induced structural discontinuities (surface cracks or voids) that must be considered in the design stage. Nevertheless, most TO algorithms cannot realistically handle these structural cracks/defects since they mainly employ classical continuum-mechanics formulations combined with the finite element method (FEM). On the other hand, peridynamics (PD), a non-local meshless approach, can effectively model any structural discontinuity without the need for an additional effort by breaking non-local interactions. In this study, we combine PD and optimality criterion-based TO methods to investigate the effect of surface cracks on the three-dimensional structural design. For a comparative study, these cracks are also modeled using FEM-TO by eliminating the elements in the cracked region. Optimal geometries and total strain energies obtained from PD are compared with those from FEM for the benchmark case with/without surface cracks. Finally, the advantage of PD is revealed for modeling structural discontinuities in TO.
Post-processing of surface topography data for as-built metal additive surface texture characterization
Surfaces of additively manufactured metal parts from powder-based processes typically show powder particle agglomerations and other features, resulting in high surface roughness. Proper characterization of those surfaces is necessary in order to assess part quality with respect to coatability, mechanical performance or corrosion resistance for use in aerospace, automotive, medical and more industrial applications. Optical surface texture measurement allows for collection of areal surface data, while the established contact stylus method only captures line profile data. When applying optical methods for surface topography measurements, proper data acquisition and post-processing in order to assess surface texture may be complex. A number of variables can be adjusted, such as different measurement settings, approaches to outlier removal, evaluated area size or form removal. This work shows the influence of selected z-range prior to measurement and the influence of choosing pre-defined outlier removal settings in MountainsMap 9.2 on selected ISO 25178-2:2021 parameters calculated from data obtained from confocal microscopy for as-built Ti6Al4V from laser powder bed fusion. The aim is to show the influence of variation in measurement and post-processing on calculated surface texture parameters and stress the importance of proper documentation in order to achieve reproducibility of data for quality management.
Functionally graded ceramics by lithography-based ceramic manufacturing (LCM)
With the development of new industries and technological processes, the use of pure materials in sophisticated applications is decreasing due to the demand of conflicting property requirements in single component. The interest on functionally graded ceramics (FGCs) that can be used under severe service conditions with high reliability has increased parallel to demand on complex advanced ceramics in various applications. Conventional methods are not totally capable of cost-effective fabrication of near-net shape FGCs with flexible and complex gradient designs. Lithography-based ceramic manufacturing (LCM) is an additive manufacturing (AM) method that works according to the principle of selective curing of photosensitive formulation according to the digital light processing (DLP) concept. The recently developed LCM multi-material printer allows fabrication of ceramic-ceramic and metal-ceramic combinations with high dimensional precision. Printing methodologies were developed to manufacture FGCs that show both discrete and continuous porosity gradient in parallel and perpendicular to deposition direction. FGC combinations were produced by developing suitable suspensions, optimizing the debinding and sintering processes according to the single material thermo-elastic properties, design, and optimization of printing processes. The main challenges and possible future possibilities in realization of FGCs by LCM will be presented.
Coordination of spatial and temporal laser beam profile towards ultra-fine feature fabrication in laser powder bed fusion
Laser powder bed fusion (LPBF) is a metal additive manufacturing technology that provides high shape and application flexibilities. Although dimensional flexibility is high in theory thanks to the non-contactless micro range processing tool (i.e., laser beam) and powder, the fabrication robustness of thin and ultra-thin features (dnominal?200 ?m) is still a challenge for the technology. In particular, geometrical fidelity and dimensional accuracy problems have been raising towards the ultra-thin fabrication segment. Although there were different studies that presented solutions for robust and sustainable fabrication strategy in ultra-thin segment in the literature, the vast majority of them focused on process itself directly, and the technological feasibility of the LPBF systems was not considered. However, without considering technological feasibility of the LPBF systems, the presented solutions in the literature are far from providing solid basis and they may mislead the users in the case of direct application. In this sense, this study mainly focused on the scanning capability of the systems for features under 200 µm dimensional range with temporal and spatial laser beam management in the case of conventional scanning strategy (contour and hatch). For this purpose, the fabrication process reduced to the two dimensions (scanning region) via the laser marking tests, and custom laser parameters, which are provided by the industrial grade open architecture LPBF system, has been used. Here, it has been reported that two different errors related to scanning performance and process parameters for continuous and pulsed wave laser emission modes, separation, and compensation of these two errors, and investigation methodology for technological feasibility of the LPBF machines. Moreover, in the pulsed wave laser emission mode, two linear parameters have been presented to optimize spatial energy distribution. Considering the results coming from the practical observations and measurements, it is possible to indicate that the technological feasibility of the utilized LPBF system should be key concern before laser or scan related parameters optimization. The results show that if correct scanning parameters have been selected in the technological feasibility window of the system, scan trajectories based on conventional hatching method can be carried out with sufficient geometrical accuracy.
Characterization of metal powder reused multiple times for laser powder bed fusion
Laser Powder Bed Fusion (L-PBF) enables the manufacturing of highly complex parts with less material consumption for being used in various industrial applications. Metal powders are commonly used as feedstock material and the powder can be reused several times. Especially in aerospace applications, the reused powder characteristics are quite important in terms of traceability over the part quality since the aerospace industry requires high-quality and reliable end-use parts. In this study, Alloy 718 metal powder, which is generally utilized in high-temperature applications in gas turbine engines due to their good creep and corrosion resistance, were characterized over a 20 series of L-PBF build cycles. The powder characterization was performed in order to investigate the flow behavior of powder reused multiple times by using several methods such as powder rheology, particle size distribution (PSD), and quantitative morphology analysis along with apparent and tap density measurements. The results showed that no major and meaningful difference was seen among 20 times reused powder in terms of PSD and their morphology whereas there is a prominent difference seen by density measurements and with shear cell measurements by powder rheology. These methods revealed that reusing powder causes worse flowability trend.
Surface roughness assessment of post-process effects on L-PBF alloy 718
Laser Powder Bed Fusion (L-PBF) is one of the promising Additive Manufacturing (AM) technologies to build relatively smooth surfaces belong to complex geometries with its overall technology readiness level. However, this may depend on the other parameters such as built orientation, support structures etc. Despite many advantages of AM, surface roughness of L-PBF’ed parts may still not be met in as-built condition the tight requirements of aviation industry. In this study, the surface roughness assessment of L-PBF’ed as-built Alloy 718 parts using virgin powder is evaluated by utilizing several post processes beyond the industrial preferences, in aviation standards. The surface roughness is consequently optimized based on orientation in order to define robust manufacturing tolerances in AM of aviation parts. Closed clearances or smooth surface profiles are perfectly needed in those parts to improve several aspects such as fatigue life span. In the scope of this study, Grit Blasting, Glass Bead Peening, Chemical Milling, Ultrapolish and some of their combinations on five different sloping angles were studied, surface quality were evaluated with profilometer in addition to weight loss effects based on the stock loss method. The outcomes of the study will be used as reference in the future works of TEI.
Energy Density Determination for L-PBFP of Ti-6Al-4V Alloy for Various Beam Diameters and Hatch Distances
It is important to determine the appropriate energy densities to achieve an ideal (defect-free) production in the laser powder bed fusion process. In this study, energy density levels for Ti-6Al-4V alloy were determined through simulations with a model using a dynamic volumetric heat source. Undesirable situations such as fusion problems, balling, excessive evaporation, and keyhole regime are accepted as criteria for the evaluation. The developed process window covers analysis for different beam diameters of 50, 80, and 100 micrometers, and hatch distances ranging from 30 to 100 micrometers. Laser power and laser scan speed range from 50 to 200 W and 250 to 1500 mm/s, respectively. The results have shown that higher laser power with low scan speed causes high evaporation and keyhole formation. On the other hand, unstable melt-pools, fusion problems and balling may be encountered for lower laser power with high scan speed. Consequently, the analysis results are to be used as a guide before further experimental tests.
Effects of design parameters on surface roughness of additively manufactured thin-walled structures
Additive manufacturing (AM) has enabled the production of complex geometries that are not possible to be manufactured through traditional subtractive methods. Among the AM technologies, laser powder bed fusion (LPBF) has gained considerable attention in many engineering industries due to its capability to fabricate components with high resolution. The benefits of LPBF technology have also been utilized in the production of thin-wall structures in the aviation industry. Many internal thin-wall surfaces are retained as-build due to inapplicability of surface enhancement methods. Therefore, surface roughness of additively manufactured thin-wall structures is thoroughly sensitive to quality of AM process. This may adversely affect the mechanical properties of the end-product. Therefore, in this study, thin-wall specimens made of CoCr are fabricated through LPBF and effects of wall thickness, build angle, and angle of the laser incidence on the surface roughness are investigated. For that purpose, printed surface topologies are analyzed using a focus variation device and relationship between the control parameters and standard surface roughness metrics is presented.
Contact-free support structures effect on dimensional deviation of LPBF printed components with overhang features
Laser powder bed fusion (LPBF) process has gained great attention in recent years since it enables the production of very complex parts with acceptable dimensional accuracy, cost and mechanical properties. Since LPBF process is a thermal process and very high thermal stresses occur during production, dimensional deviations occur especially in very thin and overhang regions. The aim of this study is to show the feasibility of using contactless supports at thin and overhang regions for reducing dimensional deviation of the final part. For this purpose, 1.5 mm thick overhang parts with 300 inclination angles with respect to build plate were manufactured with LPBF process from In718 material. Contactless supports with different amount of gaps between the overhang surface and the support (0.23, 0.31 and 0.38 mm) were used during production. The produced parts were 3D scanned with a blue light device. Results show that contactless supports are good alternative to solid supports in the production of overhang parts with LPBF method and contactless support gaps directly affect the dimensional deviation of the final part.
Heat pipe embedded cold plate design with additive manufacturing technologies
Heat pipe embedded/integrated cold plates are mostly preferred to increase the thermal conductivity of the base material to have passive thermal management in reliable products. Thanks to Additive Manufacturing (AM) Technology, it became possible to find a high conductive product by simultaneously manufacturing the heat pipe in the cold plate. In this study, the heat pipe embedded cold plate design of an electronic chassis designed for a military product has been investigated in detail. Performing this study, it is seen that there are many outstanding advantages of using AM technology compared to the conventional heat pipe embedding techniques. Thermal analysis of a 6U size cold plate with a high thermal load is performed for aluminum & copper base material and groove type heat pipe embedded aluminum cold plate (HPECP). After that, the manufacturing constraints of both techniques are compared and outstanding design capabilities with AM technology are discussed in detail. It is seen that by using AM technology, it is possible to have a lighter cold plate with improved thermal conductivity in one piece and even lower cost.
A numerical and experimental investigation on buckling behavior of additively manufactured ribbed casings
Laser Beam Powder Bed Fusion (LB-PBF) is a thermomechanical process and residual effects that occur during the process may affect the geometrical stability. Buckling is a type of failure mode for materials, that leads thin materials to buckle under compressive loads. For a more stable buckling behavior in gas turbine engine casings, ribbing structures are being used due to their high compression strength-to-weight ratio. With the advantages of LB-PBF process such as the ability to create complex ribs and reducing machining needs, it can be preferred to manufacture ribbed engine casings via LB-PBF method. In this study, different ribbed engine casings with identical volumes are designed and residual effects caused by LB-PBF are inspected. Buckling simulations are performed on the designed and process simulation-derived casings including the residual strains and stresses, and compressive tests are physically carried out on manufactured parts to compare with simulation results. Following the results of experiments and simulations, residual effects of additive manufacturing distortions over stability were found to be fundamental. It was found that isogrid ribbing yields better resistance towards buckling loads, hinting that lateral ribs contribute more to the overall stability of casings rather than horizontal ribs.
Copyright (c) 2022 Journal of Additive Manufacturing Technologies https://creativecommons.org/licenses/by/4.0/
Additive manufacturing and acoustic Emission: a brief review
Additive manufacturing (AM) or 3D printing (TDP) will be the next-generation manufacturing process replacing the traditional manufacturing process. A tiny toy to a rocket part is being manufactured by the AM. Depending on the condition of use, environment, installation, vibration, fatigue, and types of motion such as static or dynamic, material properties might change day by day. Special attention is necessary for selecting and monitoring these objects or parts for human safety. Consistent and scheduled monitoring of the 3D structure is required to show the future manufacturing process and avoid such casualties. As the demand to produce AM items has been increasing exponentially, monitoring the structural health must be taken into consideration for the safety of the users. Structural health monitoring (SHM) utilizes several non-destructive techniques and methods to detect and monitor the structure. Acoustic Emission (AE) is a great way to see the crack formation of the modern structural health monitoring (SHM) system. This study mainly focused on two topics, AM and AE. Considering AM, a brief 3D printing history and types have been discussed. Also, this study connects a novel kind of review AE and AM, as per the information from different search engines.
Introducing Additive Manufacturing Technologies Journal
We are very excited to introduce our new journal, Additive Manufacturing Technologies. The Additive Manufacturing Technologies Journal will be premier open-access journal related to all aspects of additive manufacturing technologies. Additive manufacturing (AM) has been an integral tool in product development. With the recent advancements, additive manufacturing technologies have revolutionized manufactured industry with endless range of real-world applications. Today, additive manufacturing technologies can be used for digital manufacturing of fully functional and customized production parts with complex geometries and materials directly from computer models, which is not possible to achieve with any other conventional manufacturing process. However, there remain a plethora of challenges that must be addressed to fully realize the full potentials of additive manufacturing technologies, bringing new applications and opportunities. The purpose of this journal is to publish new, exciting, and high-quality peer-reviewed research results related to all aspects of additive manufacturing and its real-world applications. The journal aims to contribute additive manufacturing community by publishing high-quality work that promotes advancement of additive manufacturing technologies. The journal publishes research papers, review articles, and special issue articles including conference proceedings. Papers relevant to the scope of the Journal of Additive Manufacturing Technologies includes - but not limited to- the following topics: - Design for Additive Manufacturing - Topology optimization applications in additive manufacturing - Additive Manufacturing processes - Modeling and simulation for additive manufacturing processes - Process monitoring and control in additive manufacturing - Novel materials for additive manufacturing - Post-processing operations - Hybrid manufacturing - Process-planning for additive manufacturing - Data analytics in additive manufacturing - Composite additive manufacturing - 3D Bioprinting - 4D printing We look forward to receiving your submissions covering all aspects of additive manufacturing technologies and applications. Sincerely yours, Bahattin Koç and Yusuf Kaynak Editors-in-Chief Journal of Additive Manufacturing Technologies
Copyright (c) 2021 Journal of Additive Manufacturing Technologies https://creativecommons.org/licenses/by/4.0/
Peridynamics-informed effect of micro-cracks on topology optimization of lightweight structures
Most structures are preferred to be light-weighted when they are used in industrial applications such as automotive, aerospace, and naval structures. Classical continuum mechanics (CCM) formulations are commonly adopted to solve the topology optimization problems. However, CCM brings about some restrictions to the modeling, analysis, and solution of complex structures with structural discontinuities, defects, and micro/macro damages. Unlike CCM, peridynamic theory provides a wider range of analysis options because of its nonlocal integration nature, which can eliminate the need for partial derivatives in the equation of motion, thereby being suitable for effective modeling of cracks, damages, etc. This paper presents an application of peridynamics based topology optimization (PD-TO) to study the effect of micro-damages for designing lightweight engineering structures. The PD-TO algorithm used herein is based on the coupling of bond-based method and Optimality Criteria (OC) topology optimization method. The structure is designed by locating various microcracks for investigating the microdamage effect on the optimal topologies. To this end, the PD-TO model is implemented using an in-house MATLAB code, and strain energy density distributions are compared between different topologies. As a result, the importance of including damage regions within the lightweight design optimization stage is revealed.
An effective parameter in the deposition of 17-4PH powder with LMD technique: scanning speed
Laser metal deposition (LMD) is a novel additive manufacturing technology that has recently been utilized in the aerospace and automotive sectors to improve performance and speed up the process by minimizing connecting operations (welding, screwing, etc.) in production. In this study, the effects of scanning speed parameter on the microstructure and microhardness of 17-4 PH stainless steel produced by LMD method were investigated. 17-4 PH and AISI 1050 materials were used as deposition and substrate, respectively. As one of the production parameters, the laser power (W), gas flow rate (L/min), and powder flow rate (rev/min) were kept constant while scanning speed varied between 10-15 mm/s. With the changing scanning speed, differences in microstructure and accordingly changes in microhardness were observed. The results showed that the effect of deposition and scanning speed on the substrate is important in the LMD production technique, and this effect significantly affects the mechanical and microstructural properties.
Powder coater monitoring for detection of anomalies in DMLM process
Additive Manufacturing (AM) is becoming more and more favorable in aerospace industry applications. However, the quality standards for this type of applications are very high, therefore a thorough investigation is required not only after manufacturing but also during the AM process. The tool introduced in this study visually demonstrates if there are any anomalies during powder coating in Direct Metal Laser Melting (DMLM) process. This tool is based on an algorithm that collects and analyzes the images of powder coating and determines whether the powder was spread evenly, or an anomaly occurred during coating. In this study, also a cross validation was carried out with the AM distortion simulation results of the corresponding test part. The same layers where an anomaly was detected in the powder coating analysis tool were investigated in the simulation results and a slight indication was observed, and that validates the outcome of the tool. This study demonstrates results of process anomalies observed in a test part build.
On the Z-dimensional accuracy of L-powder bed fusion
Laser Powder Bed Fusion (L-PBF) is one of the commonly utilized metal Additive Manufacturing (AM) modalities in highly demanding industries such as biomedical and aerospace. Among other limitations, the dimensional accuracy of the L-PBF parts hinders the adoption of this technology for a wider application. The dimensional accuracy in L-PBF depends on several factors such as beam compensation, process parameters, .stl conversion errors and shrinkage factors. The shrinkage factors are very important and needed to compensate for down-scaling of nominal dimensions. Due to the inherent nature of the process, anisotropic shrinkage occurs due to the thermal recession and the difference of the densities from the powder material and solidified layer. Although, it is generally taken into consideration for XY-plane dimensional accuracy, Z-shrinkage factors are omitted since the layer deposition is assumed to take care of the shrinkage for every layer in addition to deep melt pools to enable layer-to-layer fusion. However, in this study, it is observed that especially for long builds from AlSi10Mg powder material, dimensional errors up to a half of a millimeter may occur along Z-direction depending on the total Z-height. Therefore, a suitable Z-shrinkage factor is calculated based on the obtained experimental results and applied to all builds leading to a much more accurate results along the build direction. Moreover, the suitability of the shrinkage factors along X and Y axes is tested and confirmed.
Copyright (c) 2022 Journal of Additive Manufacturing Technologies
Effect of annealing conditions on microstructure and hardness of CoCrFeNiMn-0.18Ti high entropy alloy manufactured by electron beam melting
The success of in situ alloying whilst developing high entropy alloys (HEAs) specific to the electron beam melting (EBM) process has been stated in the literature. Secondary phases forming on FCC matrix improved the mechanical properties of EBM-built; however, their random distribution limits the further improvement in mechanical performance. Herein, post-process heat treatments were designed to observe the effects on secondary phase morphology, distribution, and microhardness of EBM-built CoCrFeNiMn-0.18Ti HEA and establish the optimized heat treatments while reducing further cost. Systematic studies revealed that an increase in solutionizing time slightly enhanced the microhardness of the alloy despite the solutionizing temperature reversely affect the mechanical properties. On the one hand, reaching a solutionizing temperature of 1300°C would not be enough to dissolve all the secondary phases within a reasonable solutionizing time of two hours. Metastability of HEAs and the complex distribution of topologically formed secondary phases slowed down phase transformations through FCC matrix. On the other hand, the microhardness of samples was successfully reattributed at 600°C by annealing. Thirty minutes and fifteen hours of annealing improved the hardness of solutionized alloy by 58 and 150% while reaching 316 HV and 487 HV, respectively.
Numerical simulation of multimaterial polymer mixing for bioprinting applications
In tissue engineering, three-dimensional (3D) functional constructs (cellular or acellular) with tailored biological properties are needed to be able to mimic the hierarchical structure of biological tissues. Recent developments in extrusion based additive manufacturing considerably improved the ability to fabricate sophisticated tissue constructs by allowing to extrude multiple materials through different printing heads. This paper investigates the flow behavior of two miscible biomaterials inside an extrusion chamber incorporated with a Kenics static mixer (KSM). A computational fluid dynamics (CFD) model for isothermal non-Newtonian fluid flow was developed to numerically analyze the flow behavior of the fluids. The power-law model was used to characterize the shear-thinning behavior of the studied biomaterials. The mixing performance of designed chamber was also investigated by varying the inlet angles and velocities as well as the effect of the number of mixing units, pseudoplastic behavior of fluids, and pressure drop throughout the fluid domain. The results indicated that the inlet angle did not have a significant impact on the mixing quality and the proposed mixing channel showed good mixing performance regardless of the inlet velocities. The mixing index increases by increasing the power-law index and the shear-thinning behavior decreases the pressure drop value compared to Newtonian fluids.
3D thermal modelling and simulation of selective laser melting
Selective laser melting (SLM) is the most common additive manufacturing (AM) method since its manufacturing abilities for metal parts. In this study, heat transfer modelling and multi-track simulations of SLM with different parameters were conducted to predict maximum temperatures and melt pool dimensions depends on parameters such as laser power, scanning speed and hatching distance. Heat transfer equations for selective laser melting was obtained and material properties was revealed as temperature dependent. Goldak volumetric laser heat source model was used as the flux source. Finite Element Analysis (FEA) simulations for different laser power, scanning speed and hatching distance were conducted in ABAQUS FEA software as it provides a parametric job possibility within its Fortran subroutines. During laser scanning, it was concluded in simulation results that powder material is melted by heat source through at least one layer and this leads interlayer connection. Moreover, maximum temperatures were found stable from the beginning to the end of the track until it achieves equilibrium regime in view of temperature distribution. Lastly melt pool dimensions/ dimension ratios were examined comparing to the literature.
Influence of laser energy density on geometrical forms produced by laser metal deposition of PH 13-8 Mo stainless steel
Additive manufacturing (AM) is getting more popular in many industries due to direct manufacturing facilities, design flexibility and effective lead time. Directed energy deposition (DED) is a variation of AM and laser metal deposition (LMD) is regarded as a DED process and it uses laser as a heat source to melt and deposit the raw material fed through a nozzle in the powder form. This paper presents a research work that investigates the forms of laser metal deposited parts in S-shaped using PH 13-8 Mo stainless steel powders. Experimental work was conducted to produce S-shaped single bead walls with main process parameters affecting the energy density. The results have been discussed by considering the energy density levels as low, medium and high. It is clear to observe that the low energy density level parameters produce no or improper S-shaped walls. However, high energy density level parameters produce relatively well deposited walls but the geometrical forms of the walls are not steady due to heat accumulation during the deposition. Balling on the deposited walls can be seen in each energy density level. This defect occurs when there is insufficient heat energy to melt and deposit the powder from the moving nozzle.
A numerical approach to assess the impact of the SLM laser parameters on thermal variables
Due to extraordinarily high heating and cooling rates, understanding the selective laser melting (SLM) process remains a challenge. To evaluate the impact of processing parameters on distinct underlying surfaces, a three-dimensional finite element model is presented. To forecast the temperature distribution inside a finite solid model, a moving Gaussian heat source was created to scan the model with temperature-dependent material properties. In the finite model, the impact of processing factors such as laser power, scan rate, and scan spacing were investigated to measure thermal variables such as cooling rate, thermal gradient, and solidification rate in a layer with solid and powder bases. The maximum track temperature was observed to be increasing over the whole track length, which had a substantial influence on the thermal gradient, cooling rate, and solidification rate. The maximum track temperature, melt pool form, and thermal variables were shown to be strongly influenced by laser power and scan speed when compared to scan spacing. Furthermore, the underlying base had a substantial influence on the observed temperature values and melt pool shape.