Chapter Three - Advanced techniques for additive manufacturing of functional microdevices

Perspectives on additive manufacturing for warhead applications

PurposeThe usage of additive manufacturing (AM) technology in industries has reached up to 50 per cent as prototype or end-product. However, for AM products to be directly used as final products, AM product should be produced through advanced quality control process, which has a capability to be able to prove and reach their desire repeatability, reproducibility, reliability and preciseness. Therefore, there is a need to review quality-related research in terms of AM technology and guide AM industry in the future direction of AM development.Design/methodology/approachThis paper overviews research progress regarding the QC in AM technology. The focus of the study is on manufacturing quality issues and needs that are to be developed and optimized, and further suggests ideas and directions toward the quality improvement for future AM technology. This paper is organized as follows. Section 2 starts by conducting a comprehensive review of the literature studies on progress of quality control, issues and challenges regarding quality improvement in seven different AM techniques. Next, Section 3 provides classification of the research findings, and lastly, Section 4 discusses the challenges and future trends.FindingsThis paper presents a review on quality control in seven different techniques in AM technology and provides detailed discussions in each quality process stage. Most of the AM techniques have a trend using in-situ sensors and cameras to acquire process data for real-time monitoring and quality analysis. Procedures such as extrusion-based processes (EBP) have further advanced in data analytics and predictive algorithms-based research regarding mechanical properties and optimal printing parameters. Moreover, compared to others, the material jetting progresses technique has advanced in a system integrated with closed-feedback loop, machine vision and image processing to minimize quality issues during printing process.Research limitations/implicationsThis paper is limited to reviewing of only seven techniques of AM technology, which includes photopolymer vat processes, material jetting processes, binder jetting processes, extrusion-based processes, powder bed fusion processes, directed energy deposition processes and sheet lamination processes. This paper would impact on the improvement of quality control in AM industries such as industrial, automotive, medical, aerospace and military production.Originality/valueAdditive manufacturing technology, in terms of quality control has yet to be reviewed.

Objective: In order to industrialize Additive Manufacturing (AM), we proposed in previous works to elaborate Industrialization Standard for AM (IS4AM). The IS4AM is a promising concept but remains very conceptual and requires more empirical validation and implementation strategies to the real-world applications. For example, several issues such as defect, fault, failure and damage can affect the AM progress at several levels: AM process, design and resulting products (quality, usability …), even the machine elements and the surrounding environment. So, we propose here a generalized concept called deterioration to overcome these issues considering real-world applications in AM technology. Methods: In order to understand the deterioration concept considering AM as a specific technology to deal with, functionality concept should be first treated. Next, we select an AM machine (Adventurer 3+, manufactured by FLASHFORGE) based on Fused Filament Fabrication (FFF) as a simple and common AM technique with the object of treating the different probable functions and their classifications. After that we define a generalized concept called deterioration to cover the different problem cases in this specific technology. For example, in certain AM applications, a small defect may lead to a rejection of the final product by the customer, which forms a big obstacle in the industrialization of this technology. In addition, damage of machine elements and surrounding environments is considered here as an additional issue when comparing to the three components (defect, fault and failure) treated in the other industries. Results: It has been found that functionality and deterioration concepts in AM are highly related to uncertainty existence, which leads to additional warnings (difficulties) when characterizing these concepts. Classification systems for functionality and deterioration levels in AM are next clarified to provide a deep relevance to AM industrialization challenges. The different illustrative examples for pure and composite Polylactic Acid (PLA) materials represent here various deterioration degrees and classes, especially when dealing with composite PLA ones. Conclusion: Uncertainty plays an important role in preventing the industrialization of AM technology. Regarding several industries, we proposed a new concept called deterioration as a novel framework to be compatible with AM technology in order to reduce the uncertainty effects which paves the way to establish the IS4AM.

Functionally graded materials (FGM) have recently attracted a lot of research attention in the wake of the recent prominence of additive manufacturing (AM) technologies. The continuously varying spatial composition profile of two or more materials affords FGM to possess properties of multiple different materials simultaneously. Emerging AM technologies enable manufacturing complex shapes with customized multifunctional material properties in an additive fashion. In this paper, we focus on providing an overview of research at the intersection of AM techniques and FGM objects. We specifically discuss FGM modeling representation schemes and outline a classification system to classify existing FGM representation methods. We also highlight the key aspects such as the part orientation, slicing, and path planning processes that are essential for fabricating FGM object through the use of multimaterial AM techniques.

The initial spread of Additive Manufacturing (AM) technologies, within the manufacturing processes, is attributed to the expiration of some of the key patents on additive printing technology, including the Stratasys’ FDM (Fused Deposition Modeling) one. In a short time, researchers, through open-source projects such as RepRap [1], have reduced the critical issues of additive processes, making 3D printing more accessible and defining new ways to use it beyond its traditional use for rapid prototyping. Moving through the early applications of additive technology in industry, which involved visualization and rapid development of prototypes, within a decade the use of AM processes for the fabrication of a wide range of functional components in a variety of industrial fields has grown exponentially.There are many benefits from introducing AM techniques into design processes, such as high level of customization and reduced waste material. The most significant benefit that researchers are investigating is the capability to produce lattice structures that would otherwise be impossible to obtain with other processes. Primarily through biomimetics, they are investigating how to mimic biological structures that are constantly evolving to optimize both weight and strength. The aerospace sector was one of the first to adopt cutting-edge AM technologies combined with topological optimization methods, that allow to redesign components by removing geometry constraints related to the traditional production methods, while ensuring the reduction of the overall weight and therefore bringing beneficial effects on fuel consumption and environmental impact. In fact, through AM technologies there is a significant improvement in the “buy-to-fly ratio”, which is the ratio between the weight of the raw material and the weight of the finished product, which in additive manufacturing tends to 1 and brings significant reductions in material waste [2]. The article illustrates the main methods of Design for Additive Manufacturing (DfAM) oriented to the aerospace sector in order to explore the possible fields of application and to suggest guidelines for the design process. Through DfAM it will be possible to explore new configurations, by diversifying existing products and creating new forms of design “materialization”. AM technologies in particular provide efficient manufacturing solutions for small production volumes, improving supply chain responsiveness through manufacturing strategies and enabling the reduction of additional logistics costs. In addition, with the implementation of the Rapid Tooling approach, AM will contribute to improving the performance of traditional mass production systems by enhancing the production speed of injection molding machines. Finally, the introduction of new tools for additive design will allow the definition of new scenarios for manufacturing oriented to produce lightweight solutions, with high levels of performance and efficiency, reducing the time between design and production, in order to reduce the time to market.KeywordsAdditive manufacturingDesignProduct sustainabilityBiomimetic

Process planning for combined additive and subtractive manufacturing technologies in a remanufacturing context

Scaffolds with gradients of physico-chemical properties and controlled 3D architectures are crucial for engineering complex tissues. These can be produced using multi-material additive manufacturing (AM) techniques. However, they typically only achieve discrete gradients using separate printheads to vary compositions. Achieving continuous composition gradients, to better mimic tissues, requires material dosing and mixing controls. No such AM solution exists for most biomaterials. Existing AM techniques also cannot selectively modify scaffold surfaces to locally stimulate cell adhesion. A hybrid AM solution to cover these needs is reported here. A dosing- and mixing-enabled, dual-material printhead and an atmospheric pressure plasma jet to selectively activate/coat scaffold filaments during manufacturing were combined on one platform. Continuous composition gradients in both 2D hydrogels and 3D thermoplastic scaffolds were fabricated. An improvement in mechanical properties of continuous gradients compared to discrete gradients in the 3D scaffolds, and the ability to selectively enhance cell adhesion were demonstrated.

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.

Recent advances in additive manufacturing (AM) have attracted significant industrial interest. Initially, AM was mainly associated with the fabrication of prototypes, but the AM advances together with the broadening range of available materials, especially for producing metallic parts, have broaden the application areas and now the technology can be used for manufacturing functional parts, too. Especially, the AM technologies enable the creation of complex and topologically optimised geometries with internal cavities that were impossible to produce with traditional manufacturing processes. However, the tight geometrical tolerances along with the strict surface integrity requirements in aerospace, biomedical and automotive industries are not achievable in most cases with standalone AM technologies. Therefore, AM parts need extensive post-processing to ensure that their surface and dimensional requirements together with their respective mechanical properties are met. In this context, it is not surprising that the integration of AM with post-processing technologies into single and multi set-up processing solutions, commonly referred to as hybrid AM, has emerged as a very attractive proposition for industry while attracting a significant R&D interest. This paper reviews the current research and technology advances associated with the hybrid AM solutions. The special focus is on hybrid AM solutions that combine the capabilities of laser-based AM for processing powders with the necessary post-process technologies for producing metal parts with required accuracy, surface integrity and material properties. Commercially available hybrid AM systems that integrate laser-based AM with post-processing technologies are also reviewed together with their key application areas. Finally, the main challenges and open issues in broadening the industrial use of hybrid AM solutions are discussed.

A big data-driven framework for sustainable and smart additive manufacturing

Additive manufacturing (AM) technologies enable near-net-shape designs and demand-oriented material usage, which significantly minimizes waste. This points to a substantial opportunity for further optimization in material savings and process design. The current study delves into the advancement of sustainable manufacturing practices in the automotive industry, emphasizing the crucial role of lightweight construction concepts and AM technologies in enhancing resource efficiency and reducing greenhouse gas emissions. By exploring the integration of novel AM techniques such as selective laser melting (SLM) and laser metal deposition (LMD), the study aims to overcome existing limitations like slow build-up rates and limited component resolution. The study’s core objective revolves around the development and validation of a continuous process chain that synergizes different AM routes. In the current study, the continuous process chain for DMG MORI Lasertec 65 3D’s LMD system and the DMG MORI Lasertec 30 3D’s was demonstrated using 316L and 1.2709 steel materials. This integrated approach is designed to significantly curtail process times and minimize component costs, thus suggesting an industry-oriented process chain for future manufacturing paradigms. Additionally, the research investigates the production and material behavior of components under varying manufacturing processes, material combinations, and boundary layer materials. The culmination of this study is the validation of the proposed process route through a technology demonstrator, assessing its scalability and setting a benchmark for resource-efficient manufacturing in the automotive sector.

Offshore renewable energy structures are subject to harsh environments with loading from wind, wave, and tides which introduce fatigue damage in corrosive and erosive environments. An effective approach that has been found to improve mechanical and fatigue resistance of engineering structures is employment of Additive Manufacturing (AM) technology. However, little research has been conducted for implementation of AM technology in offshore renewable energy structures. This study aims to collate and critically discuss the advantages that AM technology can offer to enhance the lifespan of offshore renewable energy structures. In addition to fatigue life improvement, the potential of AM technology to enhance corrosion and erosion resistance in offshore renewable energy structures has been explored. It has been found in this study that among the existing AM techniques, Wire Arc Additive Manufacturing (WAAM) offers promising potentials for life enhancement of offshore wind turbine and tidal turbine support structures. Early research into the potential of using WAAM to create corrosion resistance coatings and components highlights many benefits achieved from this new emerging manufacturing technology, but further research is required to justify the use of the processes for commercial applications. In terms of erosion and wear resistance even less research has been conducted but initial findings show that AM has the potential to add a great level of resistance compared to the wrought material. This study presents the key advantages that AM technology offers to enhance the design life and integrity of offshore renewable energy structures as a first step towards unlocking the great potentials of AM for consideration and implementation in the energy transition roadmap.

This paper aims to study the energy consumption and quality characteristics of the parts fabricated by additive manufacturing (AM) technologies with a special focus on metal AM processes. AM is a family of manufacturing techniques, which is broadly used to fabricate complex and lightweight structures. The energy savings during AM processes have a significant influence on the AM industry, only if the quality of the fabricated part meets the requirements. The quality is generally represented by the surface and dimensional quality, mechanical properties, relative density, hardness, etc. The energy saving is important for environmentally benign and cleaner production, and improved product quality is useful for its application as a functional part in the aerospace, automobile, and biomedical industries. A comprehensive review of the energy consumption and quality characteristics of AM-fabricated (with special focus on metal AM) parts was carried out. Firstly, the specific energy consumption of various AM techniques has been reviewed to address the importance of energy and cleaner production. Then, the qualifications of products fabricated by different metal AM techniques have been discussed for different materials, such as titanium alloys, steel alloys, nickel alloys, and aluminum alloys. Also, by considering the practical importance of thin-walled structures fabricated by AM, a detailed analysis of their qualification has been presented. Moreover, different optimization techniques have also been reviewed for various AM process parameters and objectives. Overall, this paper provides an overview of AM, including a survey on the energy consumption and quality characteristics with the development of AM technologies for manufacturing of quality products. Finally, several future research directions are suggested, specifically the need for a framework for metal AM processes for the fabrication of quality products with minimum energy consumption.

A comprehensive review on additive manufacturing of glass: Recent progress and future outlook

Composite additive manufacturing: An overview of current state, limitations, and progress