Additive Manufacturing Techniques in Manufacturing -An Overview

Purpose The development of additive manufacturing (AM) techniques has significantly expanded the design space for engineering structures and facilitated the practical application of novel concepts, such as meta-materials with diverse microstructures. However, in load-bearing applications—particularly in aerospace and aeroengine fields—additively manufactured (AMed) metallic materials and structures still face limitations due to the presence of inherent defects. For meta-materials, the geometric accuracy of microstructural cells is also difficult to ensure using current metal AM technologies. These defects and geometric inaccuracies can markedly affect the mechanical properties of mechanical meta-materials. Consequently, a substantial body of research has focused on investigating the mechanical behavior and performance of AMed mechanical meta-materials. This paper presents a comprehensive review of recent advancements in metal AM technologies, with a particular focus on defect characterization methods and the evaluation of strength and fatigue properties in AMed mechanical meta-materials. Design/methodology/approach This paper provides a state-of-the-art review on the AM techniques for mechanical meta-materials, defects and defect characterization methods in AMed structures, and evaluation methods of strength and fatigue properties of mechanical meta-materials. Findings Metal AM techniques for mechanical meta-materials, like selective laser melting, wire-arc AM, etc, and recently developed technologies like, online inspection during the AM process, are reviewed. The defects in AMed meta-materials, along with the corresponding characterization methods, are systematically summarized. Additionally, this paper presents a comprehensive overview of evaluation approaches for the strength and fatigue properties of mechanical meta-materials, encompassing experimental testing, theoretical modeling, numerical simulation, and machine learning techniques. Future perspectives on manufacturing and the mechanical property study of mechanical meta-materials are also given. Originality/value A systematic summary of metal AM techniques, as well as defect detection and characterization methods in AMed mechanical meta-materials, is provided. Furthermore, the paper presents a comprehensive review of the mechanical properties of mechanical meta-materials, with a particular focus on strength and fatigue performance.

Additive manufacturing (AM) has recently been accorded considerable interest by manufacturers. Many manufacturing industries, amongst others in the aerospace sector, are already using AM parts or are investing in such manufacturing methods. Important material properties, such as microstructures, residual stress, and surface topography, can be affected by AM processes. In addition, a subtractive manufacturing (SM) process, such as machining, is required for finishing certain parts when accurate tolerances are required. This finish machining will subsequently affect the surface integrity and topography of the material. In this research work, we focused on the surface integrity of Ti-6Al-4V parts manufactured using three different types of AM and finished using an SM step. The aim of this study was to gain an understanding on how each process affects the resulting surface integrity of the material. It was found that each AM process affects the materials’ properties differently and that clear differences exist compared to a reference material manufactured using conventional methods. The newly generated surface was investigated after the SM step and each combination of AM/SM resulted in differences in surface integrity. It was found that different AM processes result in different microstructures which in turn affect surface integrity after the SM process.

Research in the field of 3D printing and water industry, in particular, on the fabrication and evaluation of feed spacers produced via 3D printing, rapid prototyping or additive manufacturing (AM) techniques is presented in this thesis. Feed spacer is a mesh-like structure placed between membrane sheets to create channels for fluid flow in a spiral wound membrane module (SWM). It has an important role in the hydrodynamic conditions of a SWM, which serves to facilitate mass transfer in the feed channel by generating vortex and promoting mixing. The mass transfer is critical in reducing the concentration polarisation phenomenon in membrane processes, which is often associated with membrane fouling. However, the challenges of commercial feed spacers include the trade-off between mass transfer and pressure drop along the channel that leads to the rise in energy demand as well as their impact on membrane fouling. Many studies via computational fluid dynamics (CFD) simulations have shown that spacers with complex structures have great potential in enhancing the mass transfer. However, conventional method of spacer manufacturing by extrusion could not realise the complicated designs of spacers. In this work, the 3D printing technology is employed as a tool to fabricate novel feed spacers with structures that maximise the mass transfer while minimise the channel pressure drop. It is nevertheless important to note that there are limitations in current AM technology. A link between the design and fabrication i.e. printability and surface finish properties of spacers was established. The printability of polypropylene (PP) which is the representative material of spacers was also investigated. The fabricated spacers were evaluated in terms of flux and pressure drop. Direct observation through the membrane (DOTM) technique was also used to study the impact of different 3D printed spacers on the critical flux of particles. Among the 3 broad classes of solid, liquid, powder based 3D printing techniques, the liquid based Polyjet technique was found to give the most accurate representation of the intended design while the solid based FDM (Fused Deposition Modeling) technique produced spacers that showed the greatest deviation from the specifications. On the other hand, the improvement in mass transfer by the FDM printed spacer was unexpectedly the greatest among the three 3D printed spacers, due to the ‘randomness’ in the strand of spacer. In addition, the surface finish of the spacers was found to have an effect on the critical flux, specifically, the anisotropic surface finish of FDM and semi-anisotropic surface finish of Polyjet. Biofouling potential was discovered to be correlated to the surface roughness of samples. Among which, Polyjet and SLS printed samples have greater bacteria attachment due to their higher microscale roughness. Eventually, three design considerations for developing 3D printed novel spacers were recommended. A series of existing (i.e., taken from the literatures), modified and innovative spacer structures, compared with commercial feed spacer, were examined to identify the basis form of spacer structure with the greatest potential. Further optimization of the selected structure was conducted to improve the spacer performance. With the primary structure made up of sinusoidal curves and secondary structures consisting cylindrical protrusions along the curve, the novel spacer S12 showed an improvement of 18% at power number, Pn=106, and 25% at Pn= 105 in mass transfer compared to commercial spacer. With this optimal design, a smart multi-material spacer was developed by designing the primary structure with a rigid material and the secondary structures with flexible materials. The multi-material responsive spacer with Tangoblackplus as the flexible material was able to lower the flux decline due to bentonite fouling by 7.6% as compared to the commercial spacer and 5.2% when compared to the single rigid material spacer. This indicates that a spacer with flexible filaments has a beneficial effect on fouling reduction. The flexible properties of the selected section on the spacer allow dynamic movement under varying flow rate, which creates a “sweeping” effect that disrupts the boundary layers and prevents foulants from accumulating near spacer filaments and on the membrane surface, thereby mitigating fouling. These favourable findings have contributed as one of the pioneering work in this interdisciplinary field.

Advancements in understanding the microstructure and properties of additive manufacturing Ti-6Al-4V alloy: A comprehensive review

Purpose– The purpose of this paper is to review the current status of additive manufacturing (AM) used for tissue engineering (TE) scaffold. AM processes are identified as an effective method for fabricating geometrically complex objects directly from computer models or three-dimensional digital representations. The use of AM technologies in the field of TE has grown rapidly in the past 10 years.Design/methodology/approach– The processes, materials, precision, applications of different AM technologies and their modified versions used for TE scaffold are presented. Additionally, future directions of AM used for TE scaffold are also discussed.Findings– There are two principal routes for the fabrication of scaffolds by AM: direct and indirect routes. According to the working principle, the AM technologies used for TE scaffold can be generally classified into: laser-based; nozzle-based; and hybrid. Although a number of materials and fabrication techniques have been developed, each AM technique is a process based on the unique property of the raw materials applied. The fabrication of TE scaffolds faces a variety of challenges, such as expanding the range of materials, improving precision and adapting to complex scaffold structures.Originality/value– This review presents the latest research regarding AM used for TE scaffold. The information available in this paper helps researchers, scholars and graduate students to get a quick overview on the recent research of AM used for TE scaffold and identify new research directions for AM in TE.

Advancement in additive manufacturing (AM) allows the production of nanocomposites with complex and custom geometries not typically allowable with conventional manufacturing techniques. The benefits of AM have led to recent interest in producing multifunctional materials capable of being printed with current AM technologies. In this article, piezoresistive composites realized by AM and the matrices and fillers utilized to make such devices are introduced and discussed. Carbon-based nanoparticles (Carbon Nanotubes, Graphene/Graphite, and Carbon Black) are often the filler choice of most researchers and are heavily discussed throughout this review in combination with extrusion AM methods. Piezoresistive applications such as physiological and wearable sensors, structural health monitoring, and soft robotics are presented with an emphasis on material and AM selection to meet the demands of such applications.

Additive manufacturing (AM) technologies continuously evolve in materials and operational processes. However, challenges related to energy consumption, material reuse efficiency, and the integration of Circular Economy (CE) principles may impede the overall sustainability of AM processes. As many industrial sectors adopt AM technologies, there is a growing need for innovative tools, methods, and frameworks that guide companies toward more sustainable and circular production practices. This shift involves improving resource efficiency and fostering new Circular Business Models that emphasize material recovery, product lifecycle extension, and waste minimization. This study assesses current and future trends in the development of sustainable AM technologies for processing metal feedstock, based on a comprehensive patent analysis covering the period from 2004 to 2024. We specifically focus on the sustainability impacts of Electron and Laser Beam Powder Bed Fusion (PBF-EB, PBF-LB) and Direct Energy Deposition (DED), given their widespread industrial applications. Patents were categorized into three groups: materials, processes, and components. Furthermore, AM technologies were analyzed according to their role within the production cycle: materials preparation, pre-processing, manufacturing, and post-processing. This categorization allows for a detailed understanding of how innovations in AM contribute to more sustainable production and consumption practices by improving energy efficiency, material usage, circularity, and overall environmental impact.

Purpose Because of the significant differences in the features and requirements of specific products and the capabilities of various additive manufacturing (AM) solutions, selecting the most appropriate AM technology can be challenging. This study aims to propose a method to solve the complex process selection in 3D printing applications, especially by creating a new multicriteria decision-making tool that takes the direct certainty of each comparison to reflect the decision-maker’s desire effectively. Design/methodology/approach The methodology proposed includes five steps: defining the AM technology selection decision criteria and constraints, extracting available AM parameters from the database, evaluating the selected AM technology parameters based on the proposed decision-making methodology, improving the accuracy of the decision by adopting newly proposed weighting scheme and selecting optimal AM technologies by integrating information gathered from the whole decision-making process. Findings To demonstrate the feasibility and reliability of the proposed methodology, this case study describes a detailed industrial application in rapid investment casting that applies the weightings to a tailored AM technologies and materials database to determine the most suitable AM process. The results showed that the proposed methodology could solve complicated AM process selection problems at both the design and manufacturing stages. Originality/value This research proposes a unique multicriteria decision-making solution, which employs an exclusive weightings calculation algorithm that converts the decision-maker's subjective priority of the involved criteria into comparable values. The proposed framework can reduce decision-maker's comparison duty and potentially reduce errors in the pairwise comparisons used in other decision-making methodologies.

Sinter-based metal additive manufacturing (AM) processes that decouple the geometric shaping and consolidation of AM have several advantages over melt-based AM technologies (one-step consolidation and shaping). The sinter-based AM technologies, led by binder jetting, has the potential to significantly increase the productivity and attain more isotropic microstructures in the final product. Sinter-based AM includes the ability to cover a wide spectrum of productivity, including prototyping, low volume serial production, and high-volume mass production. Recently, several non-traditional sinter-based metal AM processes (relatively less common) have emerged. This paper will review some of these emerging and lesser-known sinter-based metal AM technologies along with a few processes based on modifications of binder jet and material extrusion techniques that have gained traction.

PurposeMaterial extrusion (MEX) is a class of additive manufacturing (AM) process based on MEX principle. In the viewpoint of Industry 4.0 and sustainable manufacturing, AM technologies are gaining importance than conventional manufacturing route (subtractive manufacturing). Because of the ease of use and lesser operation skills, MEX had wide popularity in industry for product and prototype development. This study aims to analyze energy consumption of MEX-based AM process and its influencing factors.Design/methodology/approachA group of factors were identified pertaining to MEX-based AM process. In this viewpoint, this study presents the configuration of a structural model using interpretive structural modeling (ISM) to depict dominant factors in MEX-based AM process. A total of 18 influencing factors are identified and ranked using ISM methodology for MEX process. The Impact Matrix Cross-reference Multiplication Applied to a Classification analysis was done to categorize influencing factors into four groups for MEX-based AM process.FindingsThe derivation of structural model would enable AM practitioners to systematically analyze the factors and to derive key factors which enable comprehensive energy modeling and energy assessment studies. Also, it facilitates the development of energy efficient AM system.Originality/valueThe development of structural model for analysis of factors influencing energy consumption of MEX-based AM is the original contribution of the authors.

Background: Mandibular defects caused by trauma or tumor resection pose significant challenges in both functional and aesthetic reconstruction. Additive manufacturing (AM) technologies offer promising solutions for surgical planning and personalized treatment. Objectives: This review aims to evaluate current trends in the application of AM technologies for mandibular resection and reconstruction, with a particular focus on material selection, clinical integration, and technology-specific advantages. Methods: A structured literature review was performed using PubMed, Scopus, Web of Science, and Google Scholar. Studies published between January 2020 and May 2025 were screened using the following inclusion criteria: original peer-reviewed English-language research involving AM in mandibular surgery. The exclusion criteria included review articles, non-English sources, and non-mandibular studies. A total of 77 studies met the inclusion criteria and were analyzed in this review. Results: Based on the literature review conducted from 2020 to 2025, the most common restorative methods for the mandible using additively manufactured models include reconstruction with a titanium surgical plate bent to the curvature of the edges and angle of the mandible or a personalized titanium or PEEK surgical plate made directly based on the patient’s diagnosis. Implants made of Ti-6AL-4V ELI and bioceramic scaffolds are also used in the reconstruction process. They are developed based on patient diagnostic data and effectively replace the loss of mandibular bone structure. In addition, based on models and surgical guides created using additive manufacturing techniques, the performance of autogenous grafts from the fibula or iliac crest has improved significantly when used with a titanium implant plate. Conclusions: Additive manufacturing supports highly personalized and accurate mandibular reconstruction. The advantages of these methods include a reduced overall duration of procedures, a lower health risk for patients due to less reliance on general anesthesia, a near perfect match between the implant and the remaining hard tissues, and satisfactory aesthetic outcomes. However, success depends on the appropriate selection AM technology and material, particularly in load-bearing applications.

Ceramic materials are used in various industrial applications, as they possess exceptional physical, chemical, thermal, mechanical, electrical, magnetic, and optical properties. Ceramic structural components, especially those with highly complex structures and shapes, are difficult to fabricate with conventional methods, such as sintering and hot isostatic pressing (HIP). The use of preceramic polymers has many advantages, such as excellent processibility, easy shape change, and tailorable composition for fabricating high-performance ceramic components. Additive manufacturing (AM) is an evolving manufacturing technique that can be used to construct complex and intricate structural components. Integrating polymer-derived ceramics and AM techniques has drawn significant attention, as it overcomes the limitations and challenges of conventional fabrication approaches. This review discusses the current research that used AM technologies to fabricate ceramic articles from preceramic feedstock materials, and it demonstrates that AM processes are effective and versatile approaches for fabricating ceramic components. The future of producing ceramics using preceramic feedstock materials for AM processes is also discussed at the end.

Additive manufacturing of WC reinforced maraging steel 300 composites by cold spraying and selective laser melting

Efficient contouring of functionally represented objects for additive manufacturing

Purpose The purpose of this paper is to review cases of artificial reefs built through additive manufacturing (AM) technologies and analyse their ecological goals, fabrication process, materials, structural design features and implementation location to determine predominant parameters, environmental impacts, advantages, and limitations. Design/methodology/approach The review analysed 16 cases of artificial reefs from both temperate and tropical regions. These were categorised based on the AM process used, the mortar material used (crucial for biological applications), the structural design features and the location of implementation. These parameters are assessed to determine how effectively the designs meet the stipulated ecological goals, how AM technologies demonstrate their potential in comparison to conventional methods and the preference locations of these implementations. Findings The overview revealed that the dominant artificial reef implementation occurs in the Mediterranean and Atlantic Seas, both accounting for 24%. The remaining cases were in the Australian Sea (20%), the South Asia Sea (12%), the Persian Gulf and the Pacific Ocean, both with 8%, and the Indian Sea with 4% of all the cases studied. It was concluded that fused filament fabrication, binder jetting and material extrusion represent the main AM processes used to build artificial reefs. Cementitious materials, ceramics, polymers and geopolymer formulations were used, incorporating aggregates from mineral residues, biological wastes and pozzolan materials, to reduce environmental impacts, promote the circular economy and be more beneficial for marine ecosystems. The evaluation ranking assessed how well their design and materials align with their ecological goals, demonstrating that five cases were ranked with high effectiveness, ten projects with moderate effectiveness and one case with low effectiveness. Originality/value AM represents an innovative method for marine restoration and management. It offers a rapid prototyping technique for design validation and enables the creation of highly complex shapes for habitat diversification while incorporating a diverse range of materials to benefit environmental and marine species’ habitats.