Additive manufacturing  innovations, advances, and applications

Additive Manufacturing of Materials: Viable Techniques, Metals, Advances, Advantages, and Applications

S Srivatsan, K Manigandan, and S Sudarshan

Department of Mechanical Engineering The University of Akron

Department of Industrial Engineering University of Louisville

Regional Medical Physics Department Newcastle upon Tyne Hospitals NHS Trust Newcastle upon Tyne, United Kingdom

Department of Materials Engineering and Science

South Dakota School of Mines and TechnologyRapid City, South Dakota

Università Campus Bio-Medico di Roma

South Dakota School of Mines and Technology

University of Leuven (KU Leuven)

Department of Materials Engineering University of Leuven (KU Leuven) Leuven, Belgium

W.M Keck Center for 3D Innovation The University of Texas at El Paso

Health and Rehabilitation Sciences Research Institute

University of UlsterNorthern Ireland, United Kingdom

1.2 Types of Additive Manufacturing Techniques 4

1.3 Additive Manufacturing Techniques Used for Metallic Materials 15

1.3.3 Directed Energy Deposition: Wire-Based Method 19

1.4 Use of Cold Spray for Additive Manufacturing 20

1.5 Key Ingredients for Applying and Advancing the Technology of Additive Manufacturing 21

1.5.2 Modeling, Monitoring, Control, and Process Innovation 22

1.5.5 Integration of Variables and Their Implementation 25

1.6 Advantages and Disadvantages of Additive Manufacturing 25

1.7 Technological Advances Resulting from Additive Manufacturing 26

1.8 Mechanical Properties of Additive Manufactured Materials 29

1.9 Potential Far-Reaching Applications of Additive Manufacturing 32

1.10 Emergence and Use of Additive Manufacturing in Space 38

1.10.1 Potential User Requirements and Anticipated Technologies 39

1.10.2 Ground-Based Additive Manufacturing for Space 39

Additive manufacturing (AM) has become a mainstream manufacturing process, enabling the creation of parts layer by layer from a computerized 3D model without the need for cutting tools or coolants This innovative technique optimizes design and allows for on-demand production of customized parts, earning it the title of the "third industrial revolution." The principles of additive manufacturing provide numerous advantages, including near-net shape capabilities, geometric flexibility, and reduced tooling requirements, resulting in shorter design and manufacturing cycles, as well as significant energy and cost savings This chapter reviews the viable techniques for metallic materials, highlights key components necessary for advancing this technology, and examines commonly used engineered metallic materials along with their mechanical properties, while also summarizing the broad applications of AM in education, health, and well-being.

Manufacturing plays a crucial role in wealth creation and enhancing quality of life It involves complex elements such as system design and organization, technological logistics, and operational planning and control Manufacturing technology is divided into conventional processes, which have been utilized since before 1950, and non-conventional processes that emerged and were adopted after the 1950s.

Additive manufacturing (AM) is a process that builds objects layer by layer from three-dimensional (3D) model data, distinguishing itself from traditional methods like machining and stamping that remove material from a larger stock This innovative technique, often referred to as rapid manufacturing or rapid prototyping, utilizes materials efficiently, minimizing waste while ensuring high accuracy in the final product's geometry AM enables the seamless transformation of digital designs into tangible items without the need for additional fixtures or cutting tools, facilitating the creation of complex geometries that are challenging to achieve through conventional processes The advantages of additive manufacturing pave the way for groundbreaking design innovations, essential for modern manufacturing and assembly practices.

Additive manufacturing enables the creation of environmentally friendly products by offering greater design flexibility compared to traditional manufacturing methods, which often impose significant constraints on product design.

1.11 Additive Manufacturing and Its Impact on Education 40

1.12 Impact on Well-Being and Health 41

1.14 Concluding Remarks: The Future of Additive Manufacturing 43

Additive manufacturing enhances production efficiency by optimizing schedules and minimizing waste Its capability to create complex geometries allows for the consolidation of previously separate components into a single object This topologically optimized design not only boosts product functionality but also reduces energy consumption and the reliance on fuel or natural resources for operation.

Since the early 1980s, additive manufacturing technology has undergone significant development and commercialization, leading to remarkable growth across various industries, including commercial products, aerospace, and healthcare This progress has fostered the belief that additive manufacturing will transform the manufacturing landscape and deliver substantial societal benefits Key advantages anticipated since the 1980s include enhanced production efficiency and innovation.

1 Reduced usage of raw materials and consumption of energy, key contributing factors to environmental sustainability

2 On-demand manufacturing, which presents a novel opportunity to reconfigure the manufacturing supply chain so as to offer less expensive products to end users or customers and in the process utilize minimal resources

3 Customized healthcare products to meet the specific needs of individual customers, which in turn could be expected to have a significant influence on improving the overall well- being of the population

In recent decades, numerous reviews have highlighted the advancements and results of additive manufacturing, particularly emphasizing the impact of different processing technologies in product engineering for specific applications This chapter aims to provide insights into the additive manufacturing techniques utilized for metallic materials, focusing on innovative practices, notable advancements, and their extensive potential applications.

Section 1.2 provides a cursory overview of the background of additive manufacturing pertain- ing to the emergence, key characteristics, and noteworthy advantages and disadvantages of the most viable and technologically relevant techniques.

Section 1.3 presents the most viable and applicable techniques available for engineering the manufacturing of products made from metallic materials.

Section 1.4 briefly summarizes use of the cold spray technique for the purpose of additive manufacturing.

Section 1.5 presents an overview of the key ingredients required for ensuring success in the application of additive manufacturing.

Section 1.6 offers a glimpse into the most significant advantages of putting to effective use additive manufacturing technology.

Section 1.7 provides a compelling overview of the technological advances that have resulted from the emergence and use of additive manufacturing.

Section 1.8 briefly surveys the published literature with specific reference to the mechanical properties of user-friendly additive manufactured materials.

Section 1.9 provides a useful record of the potential far-reaching applications that can result from the use of additive manufacturing.

Section 1.10 presents a short overview of the emergence and use of additive manufacturing in space.

Section 1.11 addresses the impact of additive manufacturing on education.

Section 1.12 takes an informative look at the impact of additive manufacturing on the overall well-being and health of the populations it serves.

Section 1.13 provides a short overview of the standards relevant to additive manufacturing. Section 1.14 briefly summarizes the possible future of additive manufacturing.

1.2 types of AddItIve MAnufACturIng teChnIques

The technology of additive manufacturing in essence consists of three basic steps:

1 A computerized three-dimensional (3D) solid model is developed and converted into a standard AM file format, such as the traditional Standard Tessellation Language (STL) 41 or a more recent AM format 42

2 This file is then sent to an additive manufacturing machine where it is manipulated to change both the position and orientation of the part or to simply scale the part.

3 The part is then built layer by layer on an additive manufacturing machine.

In 1988, stereolithography (SLA) introduced a layer-by-layer approach to additive manufacturing, although it initially faced challenges like poor dimensional accuracy and limited application to tactile models As technology advanced, additive manufacturing gained acceptance for prototyping, leading to the widespread adoption of the term "rapid prototyping." Over the years, various layer-manufacturing processes emerged, prompting studies to compare these innovative technologies By the mid-1990s, ongoing research solidified rapid prototyping as a crucial element in the engineering and expedited development of products.

Various terms have been suggested for these types of technology, including (1) material ingress manufacturing or additive manufacturing, (2) freeform fabrication, (3) layer manufacturing, or

Rapid prototyping, commonly associated with 3D printing, refers to the direct fabrication of physical parts from 3D models using additive manufacturing techniques This process is analogous to how an office printer transfers two-dimensional digital files onto paper The ASTM Committee F12 has played a significant role in defining and standardizing this innovative manufacturing method.

1 Additive manufacturing is defined as a process of joining materials to make objects from 3D model data, usually layer upon layer as opposed to traditional processes based on subtractive manufacturing technologies.

3D printing is a manufacturing technique that creates objects by depositing material through a print head or nozzle This innovative process involves layering printed materials to construct solid three-dimensional objects from digital models, enabling the production of virtually any shape.

In 2009, ASTM Committee F42 was formed to develop standards for additive manufacturing

Krishnamurthy

Types of Additive Manufacturing Techniques

The technology of additive manufacturing in essence consists of three basic steps:

1 A computerized three-dimensional (3D) solid model is developed and converted into a standard AM file format, such as the traditional Standard Tessellation Language (STL) 41 or a more recent AM format 42

2 This file is then sent to an additive manufacturing machine where it is manipulated to change both the position and orientation of the part or to simply scale the part.

3 The part is then built layer by layer on an additive manufacturing machine.

In 1988, stereolithography (SLA) introduced a layer-by-layer approach to additive manufacturing, initially limited by poor dimensional accuracy and primarily used for "touch" and "feel" models However, technological advancements improved accuracy, leading to the widespread acceptance of additive manufacturing for prototyping, coining the term "rapid prototyping." Over the years, various layer-manufacturing processes emerged, with studies comparing these new technologies By the mid-1990s, ongoing research established rapid prototyping as an essential element in the engineering and rapid development of products.

Various terms have been suggested for these types of technology, including (1) material ingress manufacturing or additive manufacturing, (2) freeform fabrication, (3) layer manufacturing, or

Rapid prototyping, commonly associated with 3D printing, refers to the direct fabrication of physical parts from 3D models using additive manufacturing technology This process is analogous to how an office printer transfers 2D digital files onto paper According to the ASTM Committee F12, rapid prototyping has become the most widely accepted term in this field.

1 Additive manufacturing is defined as a process of joining materials to make objects from 3D model data, usually layer upon layer as opposed to traditional processes based on subtractive manufacturing technologies.

3D printing is a manufacturing technique that creates objects by depositing material layer by layer through various printing technologies, such as a print head or nozzle This innovative process enables the transformation of digital models into solid 3D objects of nearly any shape.

In 2009, ASTM Committee F42 was formed to develop standards for additive manufacturing

Committee F42 has significantly contributed to the establishment of a terminology standard that outlines the processes for creating 3D parts from CAD files With the advancement of additive manufacturing (AM) technologies, ASTM has introduced various synonyms for AM, such as additive fabrication, additive processes, and layer manufacturing This innovative manufacturing method has gained attention from U.S industries and research universities, particularly following the formation of America Makes, a government-led consortium focused on addressing additive manufacturing challenges Supported by NASA and the Air Force Research Laboratory, America Makes plays a crucial role in coordinating efforts and preventing redundancy Similarly, the European Union has initiated its own agenda for additive manufacturing, launching a dedicated platform in the late 2010s.

Rapid prototyping (RP), an early additive manufacturing technique, enables the production of printed parts instead of just models, significantly impacting product development and production Key benefits include reduced time and costs, improved human interaction, the ability to create complex shapes difficult to machine, and a shortened product development cycle This process evolved into direct fabrication using 3D models, categorized as the most flexible form of digital manufacturing due to the absence of tool settings and wear compensation By the mid-1990s, RP became essential for rapid product development, allowing scientists and students to construct and analyze models for theoretical studies Additionally, medical professionals can create models of diseased bodies for analysis, while market researchers gain quick insights into consumer perceptions of new products.

The key steps involved in product development using rapid prototyping are shown in Figure 1.2

Rapid prototyping significantly reduces the time required to create models, allowing for the testing of multiple designs to identify and rectify flaws, ultimately enhancing performance This technology has evolved beyond model creation to produce finished products made from plastic materials, leading to its current designation as 3D printing (3DP), despite its origins in rapid prototyping.

Liquids Sheets Wires Powders fIgure 1.1 A representation of the working profiles of additive manufacturing: the layer-by-layer fabrication of a product using various unit materials 75

The rise of rapid prototyping, alongside advancements in computer-aided design (CAD), computer numerical control (CNC), and computer-aided manufacturing (CAM), has led to the development of rapid manufacturing (RM), enabling the creation of three-dimensional objects However, rapid prototyping is not always the optimal solution, particularly for larger parts that exceed the capabilities of existing additive manufacturing printers, highlighting the necessity for CNC machining processes Additionally, the range of materials suitable for rapid prototyping remains limited; while it is feasible to print components from metals and ceramics, not all commonly used manufacturing materials can be utilized.

Additive manufacturing processes utilize various methods to build and consolidate layers, primarily relying on thermal energy from lasers or electron beams to melt or sinter metal or plastic powders These processes are categorized into liquid-based, solid-based, and powder-based systems, as illustrated in Figure 1.3 This chapter focuses on the most relevant and promising additive manufacturing techniques that are shaping the future of this rapidly evolving technology across a wide range of materials Originating in the 1980s with stereolithography (SLA), additive processes have since seen numerous innovations, patent approvals, and commercial applications An overview of these diverse processes is presented in Table 1.1.

6 Laser Engineered Net Shaping (LENS™)

Parametric Design (Computer- Aided Design)

Analysis Optimization and (Computer- Aided Engineering)

Creation of Prototypes (Rapid Prototyping)

Yes fIgure 1.2 Pictorial depiction of the product development cycle 19

Liquid-based and powder-based processes have proven to be more effective than solid-based methods like laminated object manufacturing (LOM) Notably, in 2004, several advanced techniques, including electron beam melting (EBM), Laser Engineered Net Shaping (LENS), ProMetal, and PolyJet, became obsolete.

Stereolithography (SLA), developed by 3D Systems, Inc in 1986, is the pioneering rapid prototyping technique that utilizes a liquid-based process to cure photosensitive polymers with an ultraviolet laser The procedure begins with creating a model using CAD software, which is then converted into an STL file that slices the model into layers, each containing essential information for construction The resolution and thickness of these layers vary based on the equipment employed, making SLA a versatile choice for precise prototyping.

Melting Polymerization Laminated object manufacturing

Fused deposition modeling Stereolitho- graphy PolyJet

Laser Engineered Net Shaping (LENS) is a cutting-edge 3D printing technology that utilizes metal powders to create intricate structures This innovative process falls under the broader category of additive manufacturing, which encompasses various techniques for layer-by-layer fabrication Understanding the different manufacturing technologies and their acronyms, along with their years of development, is essential for grasping the evolution of 3D printing.

3D printing, also known as 3DP, was introduced between 1985 and 1997 but was discontinued in 1999 This innovative technology uses an ultraviolet laser to solidify resin at specific locations, allowing for the creation of complex structures while supporting overhanging elements After each layer is completed, the platform is lowered, and any excess resin is drained for reuse Over the years, advancements led to the development of microstereolithography, which enables layer thicknesses of less than 10 microns, significantly enhancing resolution and detail in printed objects.

Microstereolithography is a cutting-edge technique that enables the creation of three-dimensional microstructures, paving the way for ultra-dense routing in structural electronic substrates with dimensions reaching the micron level This innovative technology has opened up numerous applications across various sectors, including consumer electronics, medical devices, and defense systems.

1 Camouflaged sensors that can be hidden in plain sight for homeland security purposes

2 Dynamically adaptive prosthetics in which comfort and fit can be monitored and adjusted

3 Electronics embedded in structural components of a vehicle or building

4 Implantable electronics consisting of biocompatible materials

5 Microsystem packaging that requires high spatial resolution to create intricate cavities

6 Physically small, yet electronically large, 3D antennas that offer improved performance

7 Wearable electronics that are made to fit a specific industry

The key components or parts of a stereolithography machine are shown in Figure 1.4.

Additive Manufacturing Techniques Used for Metallic Materials

Additive manufacturing began with organic materials but gradually gained applicability for the manufacture of metallic materials when the technique was able to meet the following requirements:

2 Efficiency necessary for the manufacturing process

X - Y Table fIgure 1.9 Key LENS components and their roles in the process 75

Several commercially viable additive manufacturing techniques have emerged, primarily due to their numerous advantages Many of these methods have been specifically developed or adapted for metallic materials, building on existing techniques used for polymers The additive manufacturing systems for metallic materials can be categorized based on various criteria.

Additive manufacturing commonly utilizes a range of metallic materials, including titanium, aluminum, tool steels, super alloys, stainless steel, and refractory metals, as detailed in Table 1.3 Additionally, Table 1.4 outlines various manufacturers and their specialized equipment, highlighting the diversity in manufacturing systems, which can be categorized into three main types.

Ti-6Al-4V Al-Si-Mg H13 IN625 316 and 316L MoRe

ELI titanium 6061 Cermets IN718 420 Ta-W

CP titanium — — Stellite 347 Co-Cr

Gamma-titanium aluminide — — — PH 17-4 Alumina

Source: Frazier, W.E., J Mater Eng Perform., 23, 1917–1928, 2014. tAble 1.4 representative Additive Manufacturing equipment, processes, and sources of energy system equipment process energy source

Powder bed ARCAM Electron beam melting Electron beam

EOS Direct metal laser sintering Yb-fiber laser

Concept laser cusing Selective laser melting Fiber laser

MTT Selective laser melting Fiber laser

Phoenix System Group Selective laser melting Fiber laser

Renishaw Selective laser melting Laser

Realizer Selective laser melting Laser

Matsuura Selective laser melting Fiber laser

Powder feed Optomec (LENS) Laser engineered net shaping Fiber laser

POM DMD Direct metal deposition Disk laser

Accufusion laser consolidation Laser cutting Nd:YAG laser

Irepa laser Laser deposition Laser cladding

Huffman Laser deposition CO 2 cladding

Wire feed Sciaky Electron beam deposition Welding

MER plasma transferred arc Plasma-transferred arc selected free-form fabrication

Plasma transferred arc using two 350A DC power supplies

Source: Frazier, W.E., J Mater Eng Perform., 23, 1917–1928, 2014.

Overall, the source of energy (arc, electron beam, or laser beam) for each feed system is the key to governing operation of the system.

Powder bed fusion technology, which originated from selective laser sintering (SLS), has evolved into various techniques that utilize different mechanisms for binding powders and layers Key methods include selective laser sintering and the more commonly used direct metal laser sintering (DMLS), both of which employ laser beams with powder beds Additionally, electron beam melting (EBM) substitutes laser beams with electron beams The integration of an inkjet head with a powder bed system has led to the development of 3D printing A schematic representation of the generic powder bed system utilized in additive manufacturing is illustrated in Figure 1.10.

The fabrication process involves essential components, including a laser scanning system, powder delivery system, roller, and fabricated piston Before fabrication begins, the powder delivery piston ascends while the fabrication piston descends by a layer thickness The powder is then evenly distributed and lightly compacted by the roller onto the surface of the fabrication piston.

The laser beam selectively melts powder on a bed, guided by a scanner system, layer by layer, until a solid three-dimensional component is formed After each layer, the fabrication piston descends to apply a new layer of powder, continuing this process until completion Once finished, the piston elevates the final object, and any excess powder is brushed away for reuse after proper treatment A key advantage of the powder bed fusion system is that it eliminates the need for support structures, which are typically used to enhance thermal pathways and control part geometry An overview of the direct metal laser sintering technique is illustrated in Figure 1.11.

Powder Delivery System fIgure 1.10 The key components and their role in the powder bed system used in additive manufacturing of metallic materials 20

This system features a large build volume, as its powder feed mechanism allows for the construction of larger-scale components compared to traditional powder bed units In this process, metal powder particles are delivered through a nozzle onto the build surface, where a laser melts one or more layers of powder into the desired shape This technique is repeated to form a solid three-dimensional object, with two variations of the system available.

1 The work piece remains stationary while the deposition head moves.

2 The deposition head remains stationary while the work piece is moved.

The two most noticeable advantages of using this system are the following:

2 The ability to refurbish both worn and damaged components

The powder feed system, illustrated in Figure 1.12, utilizes lasers to effectively process various metallic alloys, such as titanium, nickel-based superalloys, stainless steels, and tool steels, all of which are readily available in the necessary powder form Ongoing research and development have led to the advancement of two primary techniques in this field.

1 Laser Engineered Net Shaping (LENS), which was initially developed at Sandia National Laboratories (Albuquerque, NM) in the 1990s

2 Direct metal deposition (DMD), which was developed by the POM Group, Inc (Auburn Hills, MI)

The primary distinction between the two techniques is found in their machine control and implementation specifics Direct metal deposition enables processing in an open atmosphere, utilizing local shielding for the molten metal In this method, metal powders are delivered and distributed via an inert gas carrier, which protects the molten metal pool from oxidation while promoting optimal layer-to-layer adhesion for improved surface wetting.

Fabrication Piston Part fIgure 1.11 Visualization of the various parts involved in direct metal laser sintering (DMLS) 75

1.3.3 d iRected e neRgy d epoSition : w iRe -b aSed M ethod

Directed Energy Deposition (DED) is an innovative additive manufacturing technique that utilizes solid wire feedstock instead of traditional metal powders A notable advancement in this field is Electron Beam Freeform Fabrication (EBF3), developed by Lockheed Martin in 1999 and publicly revealed in 2002 This technology has since been further researched and enhanced at NASA Langley Research Center, focusing on the production of unitized structures from aerospace materials.

Laser fIgure 1.12 Key components of the powder feed system used for additive manufacturing of metallic materials 20

Deposition Layers Substrate fIgure 1.13 Simple line diagram illustrates the principle behind the wire feed system used for additive manufacturing of metallic materials 20

Electron Beam Freeform Fabrication (EBF3) is a technique akin to laser engineered net shaping, utilizing electron beams as the heat source Typically conducted in a vacuum environment (10⁻⁴ torr or lower), this method employs a metal wire feed system to supply feedstock to the molten pool The precision of electron beam control allows for effective synchronization with highly reflective materials Ongoing research and development have optimized the process, achieving wire feedstock consumption efficiencies of up to 100% and power usage efficiencies of at least 95%.

The National Aeronautics and Space Administration (NASA) has two types of EBF3 systems:

1 Ground-based—The ground-based system has a dual-wire feed system that can be loaded with either fine or coarse wire to achieve various feature definitions Alternatively, two different alloys can be used to produce compositional gradients or components made from multiple materials.

2 Portable—The portable system has a single wire feeder and can be used for finer metal wire; it has high precision in positioning compared to the ground-based system, making it ideal for the fabrication of smaller parts having intricate detail.

NASA operates two portable EBF3 machines, with one having been tested on a microgravity research plane The second machine is actively utilized for various activities aimed at developing feasible in-space manufacturing applications.

Use of Cold Spray for Additive Manufacturing

Cold spray technology is advantageous for applications involving heat-sensitive substrates or hard-to-reach areas, such as small cylinders and tubes, primarily to enhance corrosion resistance This process produces dense, oxide-free deposits with satisfactory mechanical properties It involves heating a pressurized carrier gas, typically nitrogen or air, which is then passed through a convergent-divergent nozzle to create a supersonic gas jet The spray material, usually in powder form, is injected into this gas jet either upstream or downstream, allowing for effective coating in challenging environments.

Vacuum Chamber fIgure 1.14 Key components and their roles in the electron beam freeform fabrication technique 75

The formation of a well-bonded and dense deposit in cold spray processes depends on the specific minimum particle velocity required for each material, influenced by the process temperature A material's ability to plastically deform upon impact is crucial; less ductile materials necessitate higher particle velocities for effective bonding Therefore, it is essential that the cold spray powder mixture includes at least one material capable of easily deforming when it strikes the substrate surface.

Cold spray technology is gaining traction as a key enabler for 3D printing and additive manufacturing, as traditional methods often involve subtractive techniques that remove material from bulk shapes Unlike these conventional processes, additive manufacturing constructs objects by precisely layering materials based on a 3D digital model The quality of complex 3D shapes is determined by the resolution of the spot size, with smaller sizes yielding better results, making laser beams on powder beds the preferred choice for intricate geometries using special metal alloys Although cold spray deposition currently has a minimum spot size of 4 mm, which is adequate for remanufacturing and rapid prototyping, finer footprints are often necessary for achieving precise finished components With ongoing advancements in additive manufacturing, cold spray is becoming increasingly reliable and practical for producing engineering components, even at lower temperatures.

Key Ingredients for Applying and Advancing the Technology of Additive Manufacturing

the teChnology of AddItIve MAnufACturIng

Significant progress has been made in the further development of techniques intrinsic to additive manufacturing, but some of the challenges that remain to be addressed are listed below: 85,86

1 Limited amount of materials available for use in additive manufacturing processes

2 Relatively poor accuracy of the part or component caused by the “stair-stepping” effect

3 Insufficient repeatability and consistency in the end part that is produced

4 A lack of both qualification and certification methodologies for additive manufacturing processes

Advanced manufacturing techniques now enable the fabrication of complex-shaped products without the need for tools, dies, or molds, resulting in efficient and cost-effective production that meets all functional requirements This innovation significantly reduces fabrication time and production costs Ongoing research aims to accelerate the transition of 3D printing from rapid prototyping to additive manufacturing, utilizing advanced materials with enhanced properties.

2 Intrinsic ability to generate fine features (less than 100 àm)

Key factors influencing additive manufacturing technology are illustrated in Figure 1.15 The following subsections will delve into these elements, highlighting existing gaps and current requirements in the field.

Additive manufacturing technologies offer unique capabilities such as the ability to fabricate complex shapes, customize materials and properties, and deliver functional complexities These features empower designers to explore innovative applications; however, there is a pressing need for advanced design tools that effectively represent the functions and material interactions inherent in additive manufacturing Developing these design tools is essential for maximizing the potential of this transformative technology.

Tools that can further aid designers in exploring designs made possible by additive manufacturing, particularly with regard to representations of shapes, properties, processes, and other related variables

Simultaneous product and process design, integrated with multifunctional design approaches, enhances efficiency and innovation in manufacturing Additionally, assessing life-cycle costs is crucial for understanding the financial implications of product development The impact of additive manufacturing on components and finished products must also be evaluated to optimize performance and sustainability.

To enhance design capabilities, CAD systems must be adapted to address the limitations of parametric boundary representations and solid modeling in handling complex geometries and diverse materials Additionally, additive manufacturing necessitates advanced simulation capabilities for primitive shapes, various materials, and functionally graded materials It also requires multi-scale modeling and inverse design tools to effectively manage intricate process-structure-property relationships, alongside improved finite element analysis software to optimize the utilization of available resources.

1.5.2 M odeling , M onitoRing , c ontRol , and p RoceSS i nnovation

Recent advancements in technology have made the modeling, sensing, and control of additive manufacturing processes a top priority for harnessing its vast potential applications Understanding the transport phenomena in these processes requires comprehensive modeling of temperature, stress, and composition history, which poses significant challenges Accurately predicting microstructures and fatigue properties resulting from additive manufacturing is complicated by extreme heat and cooling rates that lead to unique material transformation regimes Specifically, the melting and recrystallization of polymeric materials remain inadequately understood, hindering the development of robust mathematical models Therefore, a deeper understanding of the physics of polymeric materials is crucial for effective modeling, supported by advancements in supercomputing capabilities.

System integration and cyber implementation

Modeling, monitoring, control, and process

Effective functioning of additive manufacturing for metallic materials relies on key elements, including characterization and certification Current modeling efforts have significantly influenced this field, yet complex process models frequently need simplification to lower-order models for real-time application and process control There remains a substantial gap between advanced high-fidelity modeling research and the practical implementation of online process control.

Additive manufacturing faces significant challenges, particularly limited access to the build chamber and the demand for high computing power Effective sensing in additive manufacturing processes is essential to address these issues.

1 In situ measurement of temperature, cooling rate, and residual stresses

2 Calibration of all optical sensors used for the purpose of high-accuracy measurements

3 In-process monitoring of not only the geometric dimensions but also the surface quality of the finished layers

High-speed infrared thermography is essential for predicting microstructures by analyzing grain size related to melt pool characteristics For effective process control in additive manufacturing, images must be processed at a minimum speed of 30 kHz This presents the challenge of utilizing the acquired information effectively.

1 Online process control for both material composition and phase transformation

2 Repair of existing defects, such as the presence of pinholes or porosity, microscopic cracks, and segregation

The integration of control algorithms with existing additive manufacturing equipment poses a significant challenge to the cost-effective implementation of real-time process control To enhance throughput and enable multi-material fabrication capabilities, it is essential to address these integration issues effectively.

1 Development of multiple-nozzle array print heads and machines capable of integrating multiple additive manufacturing processes

2 Subtractive and finishing processes intrinsic to the technique of conventional manufacturing

A recent and noticeable additive manufacturing process innovation is in the domain of 3D bioprinting The challenges related to the printing of 3D tissue scaffolds include the following:

1 Biophysical requirements specific to the scaffold’s structural integrity, strength stability, and degradation, as well as cell-specific pore shape, size, porosity, and interarchitecture

2 Biological requirements pertinent to both cell loading and spatial distribution, as well as the attachment of cells, their growth, and the eventual formation of new tissues

3 Mass transport considerations with specific reference to topology and interconnectivity

4 Anatomical requirements with specific regard to anatomical compatibility and geometric fitting

5 Manufacturability requirements with reference to the overall ability of the process (e.g., availability of biomaterials coupled with the feasibility of printing) and effects of the process (e.g., warping, distortion, and overall structural integrity)

Ongoing studies have shown that printing in vitro biological constructs imposes a requirement for the following:

1 Development of a new generation of biomaterials in the form of bioink for (a) dispensing with cells (a cell delivery medium), (b) growing with cells (support as an extracellular matrix), and (c) functioning with cells (in the role of biomolecules)

2 Developments in engineering (vs developments in biology) to fill the gap created by a lack of knowledge in biology

3 Commercialization of bioprinting tools so as to be able to make 3D heterogeneous structures in a viable, reliable, and reproducible manner

4 Four-dimensional bioprinting models (obtained by embedding time into the 3D bioprinting models), including stem cells having a controlled release of the biochemical molecules for exercising control of (a) complex tissues, (b) organs, (c) cellular machines, and (d) human- on-a-chip devices

Intense research and development in the specific domain of materials are necessary to

1 Broaden the selection of suitable or appropriate materials.

2 Prepare a database on the mechanical properties of the parts fabricated by additive manufacturing.

3 Determine any and all of the existing interactions occurring between materials and process parameters.

Developing new alloys and engineering materials in metallurgical and materials engineering can take over a decade, particularly for applications in additive manufacturing where high mechanical strength and corrosion resistance are crucial Significant advancements are necessary in the preparation of powder feedstock and the creation of metallic and non-metallic inks with optimal rheological properties for submicrometer resolution Additionally, the development of ceramic slurries is vital for paste-extrusion-based additive manufacturing, alongside the innovation of new biomaterials for cell delivery and bioprinting applications.

In a production environment, rigorous certification is essential, covering equipment, materials, personnel, quality control, and logistics For manufacturing processes to gain acceptance in industry, the repeatability and consistency of parts are crucial, especially with advancements in additive manufacturing technology However, the inability to guarantee material properties for specific processes hinders its adoption, as companies often doubt whether the parts will meet necessary mechanical properties and dimensional accuracy This challenge arises because current additive manufacturing systems are primarily designed for rapid prototyping rather than the functional requirements of fabricated parts.

A lack of well-established standards has contributed to the following:

1 The material data reported by the various companies are often not comparable.

2 Various users of the additive manufacturing technology utilize different process parameters when operating their equipment consistent with their own preferences and needs.

3 There appears to exist minimal repeatability of results between suppliers and the service bureaus.

4 Only a few specifications are available that end users can reference.

1.5.5 i ntegRation oF v aRiableS and t heiR i MpleMentation

Advantages and Disadvantages of Additive Manufacturing

Additive manufacturing, despite limited commercial realization compared to traditional manufacturing processes, presents several key advantages, including enhanced design flexibility, reduced material waste, and the ability to create complex geometries that are difficult or impossible to achieve with conventional methods.

Additive manufacturing enhances material efficiency by constructing parts layer by layer, in contrast to traditional subtractive manufacturing, which requires significant material removal This method not only optimizes the use of raw materials but also allows for the minimal processing and reuse of leftover materials.

Additive manufacturing enhances resource efficiency by eliminating the need for auxiliary tools like jigs, fixtures, and coolants, which are typically required in conventional manufacturing This allows small manufacturers to produce a diverse range of parts locally, closer to their customers, thereby improving supply chain dynamics.

Additive manufacturing offers remarkable part flexibility, enabling the production of complex features without tooling constraints This innovation allows for the creation of single-piece components that do not compromise functionality for manufacturing ease Additionally, it is now feasible to design parts with varying mechanical properties, such as flexibility at one end and stiffness at the other, paving the way for novel design innovations.

Additive manufacturing offers significant flexibility in production by eliminating the need for expensive setups, making it cost-effective for small batch production The quality of parts is primarily determined by the manufacturing process rather than the operator's skill, enabling production to align closely with customer demand Additionally, this technology resolves issues related to line balancing and production bottlenecks, as complex components can be produced seamlessly as single pieces.

Additive manufacturing, however, cannot fully compete with conventional manufacturing, especially in the domain of mass production, primarily because of the following: 59

Additive manufacturing processes typically utilize liquid polymers or powders infused with resin or plaster to create objects layer by layer However, these materials impose limitations on the size of objects that can be produced, as they often lack sufficient material strength for larger builds Additionally, the time required to complete the construction of large items makes them impractical for many applications.

Additive manufacturing processes frequently result in parts with a rough and ribbed surface finish, primarily caused by the stacking of plastic beads or large powder particles This inherent imperfection necessitates additional surface preparation, which can be achieved through machining or polishing to achieve a smoother appearance.

Additive manufacturing equipment often comes with a significant initial investment, with entry-level 3D printers typically priced around $5,000 and high-end models reaching up to $50,000 It's important to note that these costs do not encompass additional expenses for accessories, resins, and other necessary materials for operation.

In recent years, researchers across universities, government labs, and various industries have focused on enhancing additive manufacturing processes to address existing limitations Despite these advancements, it is improbable that additive manufacturing will completely replace traditional manufacturing methods Instead, it is expected that many additive manufacturing techniques will increasingly serve as complementary technologies, facilitating the production of replacement parts for equipment in prolonged use.

Technological Advances Resulting from Additive Manufacturing

Additive manufacturing, often called the "third industrial revolution," offers significant control over the composition, shape, and functionality of products, enabling high levels of personalization This innovative technology allows for cost-effective mass customization and the production of complex items that traditional manufacturing methods struggle to achieve By leveraging additive manufacturing, products can be efficiently created to meet diverse consumer needs.

1 In a broad range of sizes (from nanometer to micrometer scale to tens of meters)

2 From a variety of materials (metals, polymers, ceramics, composites, and even biological materials)

3 With numerous functionalities (such as load-carrying brackets, energy conversion structures, and tissue-growing scaffolds)

The science and technological capabilities of additive manufacturing have made possible its use in a wide spectrum of applications, including the following:

High-strength, lightweight aerospace structures having material gradients

High-power, high-energy-density microbatteries

Products having embedded multi-material sensors and actuators

Turbine blades having internal cavities

These applications represent only a few of the opportunities offered by the technological capability and power of additive manufacturing to print complex shapes that have a controlled composition and functionality 85,86

Additive manufacturing enables the production of complex parts with functionally graded materials (FGMs), offering a distinct advantage over conventional manufacturing methods This technology allows for the precise delivery of various materials to specific areas during the building process, facilitating the creation of components with tailored compositions Additionally, additive manufacturing provides the flexibility to control a part's material properties, enhancing its functionality.

1 Grading tungsten carbide for the primary purpose of enhancing its erosion resistance

2 Grading cobalt for the purpose of enhancing its ductility

Additive manufacturing processes can control and optimize the properties of the part being built

A practical application of material engineering can be seen in pulleys designed with increased carbide concentration near the hub and rim for enhanced hardness and wear resistance, while featuring reduced carbide levels in other areas to improve compliance Another significant example is the nose of a metallic missile cone, which utilizes ultra-high-temperature ceramic graded to a refractory metal, allowing it to withstand extreme external temperatures while maintaining a secure attachment to the metallic structure.

Additive manufacturing is rapidly advancing, enabling the creation of parts that can sense, react, compute, and behave predictably through precise programming of active materials This technology allows for the production of active systems that integrate both active and passive substructures, particularly benefiting applications in the biomedical field It has been effectively utilized to fabricate bioabsorbable, biocompatible, and biodegradable tissue scaffolds, as well as in vitro biological constructs that incorporate living cells and biological compounds.

Many of the advancements in both consumer and engineering manufacturing have been related to the following:

Technological intersections of low-cost computer-based computational capability

The ease of using CAD software

Low-cost, high-precision platforms and controllers

Availability of a variety of technologically viable additive manufacturing techniques

Technological advancements in methods and materials are largely driven by continuous research across industry, government laboratories, and academia, with a focus on expanding the consumer market The rise of low-cost additive manufacturing technology is making it increasingly accessible, catering to a diverse range of end-users This innovation is fostering significant progress in materials science, materials engineering, and manufacturing technology, while also enhancing design and development processes tailored to meet specific end-user requirements.

Additive manufacturing is revolutionizing the manufacturing industry by integrating with conventional methods, though it is unlikely to fully replace them in the near future A notable example is the hybrid process that combines laser metal deposition with CNC machining This technology supports high-volume production, particularly in the fabrication and repair of dies and molds for processes like injection molding Currently, over 63 companies worldwide provide more than 66,000 professional-grade additive manufacturing systems across eight industrial sectors, with consumer products and electronics leading at 21.8%, followed by automotive parts at 18.6%, and medical applications at 16.4% The transition from industrial prototypes to functional engineering parts has spurred the development of new engineering standards In 2013, sales of metal additive manufacturing machines surged by 76%, contributing to a market growth of over $3 billion for 3D printing products and services, a 35% increase from 2012.

The 3D printing industry has experienced remarkable growth in recent years, driven by affordable and customizable manufacturing solutions Technological advancements and decreasing costs have expanded the applications of 3D printing, with the market reaching approximately $2 billion globally in 2012 and $3 billion in 2013 By 2014, the U.S 3D printer market was nearing $4 billion, showcasing a compound annual growth rate (CAGR) of 22.8% from 2009 to 2014 Key sectors, particularly medical/dental and aerospace, are the primary consumers of 3D printing technology, utilizing it for both prototyping and manufacturing Aerospace companies, in particular, are leveraging 3D printers for testing and certification as they prepare for large-scale production.

Functional parts (29%) Tooling components (5.6 %) Patterns for metal castings (9.5%)

Patterns for prototype (10.9%) Fit and assembly (19.5 %) Presentation models (8.7 %)

Visual aids (8.7%) Other (2%) Education/research (6.1%)

The 3D Printing and Additive Manufacturing industry continues to evolve, as highlighted in the Annual Worldwide Progress Report by Wohlers Associates In 2013, various applications of additive manufacturing systems were documented, illustrating significant advancements and diverse uses in the field This report serves as a comprehensive overview of the industry's growth and technological developments, emphasizing the increasing relevance of 3D printing across multiple sectors.

Additive manufacturing significantly enhances economic sustainability compared to traditional manufacturing methods by enabling the creation of complex structures that are otherwise impossible to achieve Key advantages include just-in-time production, reduced material waste, lower energy consumption, and faster time to market Notably, this layer-by-layer approach minimizes material wastage, particularly in aerospace component manufacturing, where conventional techniques can result in up to 90% waste from titanium alloys By reducing waste generation, additive manufacturing also decreases the energy needed for producing titanium materials Furthermore, it allows for the easy production of intricate shapes without the need for tools, dies, or molds, thereby shortening fabrication time and cutting costs The emergence of digital additive manufacturing (DAM) empowers manufacturers to adapt product designs swiftly without the constraints of investing in new physical tools typical of conventional processes.

Mechanical Properties of Additive Manufactured Materials

The published literature reveals a significant lack of information regarding the mechanical properties, performance, and behavior of materials produced through additive manufacturing techniques Beyond the benefits of lower production costs, reduced energy consumption, and sustainability, understanding the mechanical behavior of additive manufactured products is crucial for their ongoing selection and use in critical applications across aerospace, ground transportation, and the medical field In 2010, the Edison Welding Institute established the first Additive Manufacturing Consortium (AMC) in the United States, attracting participants from industry, government, nonprofit research organizations, and universities to share ideas aimed at fostering innovation Key aspects necessary for engineering improvements in this field have been identified and are essential for advancing additive manufacturing technology.

1 Availability of material property databases

2 Process-model compensation to account for distortion and accuracy

3 Process sensing, control, and nondestructive evaluation

4 Clear and affordable paths for certification and quantification

5 Bigger, faster, and more capable equipment

The National Additive Manufacturing Innovation Institute (NAMII) has recently been established to promote advancements in additive manufacturing, receiving funding from several key U.S government agencies, including the Department of Commerce, Department of Defense, Department of Energy, National Science Foundation, and NASA, alongside contributions from industry partners, nonprofit organizations, and academic institutions.

Understanding the microstructural evolution of various additive manufacturing processes is crucial, as it significantly impacts the mechanical properties and performance of the final product Research indicates that the microstructure of additive manufactured metallic materials differs markedly from that of conventionally manufactured ones Key differences include distinct layer patterns, heat-affected zones (HAZs), directional grains, and intricate microstructural features within each grain.

The titanium alloy Ti6Al4V, produced through Laser Engineered Net Shaping (LENS), exhibits columnar grains aligned with the deposition direction due to heat extraction from the substrate Macroscopic heat-affected zones are prominent at the interface between the LENS deposit and the substrate, while microscopic heat-affected zones display coarse characteristics between layers, resulting from the reheating of previous layers during subsequent deposition This layered microstructure, characterized by fine microscopic heat-affected zones, contributes to the overall non-uniformity of the additive manufactured materials, leading to variations in properties across different orientations Notably, a study indicated that the yield strength and ultimate tensile strength of the additive manufactured titanium alloys surpass typical values for wrought Ti6Al4V, though ductility is slightly lower Anisotropy in mechanical properties, including yield strength and ductility, is linked to the build direction, with static properties of additive manufactured Ti6Al4V being comparable to those of wrought products.

A recent study highlighted significant differences in the properties and microstructure of Ti6Al4V alloy produced using electron beam powder bed (EBPB) and laser beam powder bed (LBPB) techniques The morphology and severity of porosity varied notably between the two methods, with LBPB resulting in irregularly shaped pores, while EBPB produced predominantly spherical porosity Surface defects were identified as harmful to the alloy's high-cycle fatigue resistance Interestingly, the study found that while porosity was present, it was not the primary factor affecting fatigue crack growth performance; instead, the alloy's microstructure played a more critical role Additionally, the application of hot isostatic pressing (HIPing) to close porosity did not significantly impact fatigue crack growth resistance.

In their as-fabricated state, nickel-based alloys exhibit a columnar microstructure with grains measuring up to 20 µm in width Following hot isostatic pressing, these columnar grains undergo recrystallization, while the metastable γʹ precipitates (Ni3Nb) gradually dissolve The resulting microstructures and mechanical properties vary significantly based on the additive manufacturing technique employed, as highlighted in Table 1.5, which details the static mechanical properties of processed titanium alloy Ti-6Al-4V.

The elongation percentages for various microstructural architectures were recorded, revealing values of 15.0%, 11.4%, 13.9%, 13.2%, and 13.9%, which facilitate advancements in microstructural design The static mechanical properties of the additive manufactured nickel-based superalloy IN625 indicate that, in its as-fabricated state, its ductility matches that of wrought and annealed versions, with only a slight decrease in yield strength However, after hot isostatic pressing, the yield strength dropped by 26%, while ductility improved by over 57% Comparatively, the shaped metal deposition (SMD) IN718 alloy demonstrated superior mechanical properties compared to its as-cast form, yet still fell short of the performance achieved through additive manufacturing Overall, the tensile strength and elongation of all additive manufactured materials surpassed those of the as-cast equivalents.

Additive manufactured components exhibit superior properties compared to those made through conventional methods, yet issues such as shrinkage, porosity, and residual stresses can significantly impact their static and dynamic characteristics The effectiveness of post-processing techniques, such as hot isostatic pressing and heat treatments, is crucial for mitigating these issues and improving material ductility However, the specific processing conditions and resulting microstructures may lead to unexpected outcomes from traditional post-processing treatments To achieve optimal properties and performance in additive manufactured materials, careful consideration of these factors is essential.

1 Judicious selection of the appropriate additive manufacturing process

2 Tailoring the fabrication condition, post-processing conditions, and key control parameters

The surface finish of an additive manufactured part is significantly affected by the equipment used, build direction, and process parameters According to Martukanitz and Simpson, the overall quality of the surface can be correlated with both the build data and feature definitions Typically, an increase in build rate leads to a decrease in feature quality or resolution, which is crucial for fatigue-critical applications.

Electron beam melt + hot isostatic pressed 330 770 69

Mechanical properties of Additive Manufactured nickel-based superalloy In718 104 process yield strength (Mpa) tensile strength (Mpa) elongation (%)

Electron beam 580 910 22 parts, produced through high-deposition-rate additive manufacturing, require post-process surface finishing to achieve optimal performance When processed correctly, the static mechanical properties of these additively manufactured metallic materials can match those of conventionally fabricated components The high cooling rates inherent in additive manufacturing help minimize partitioning and promote finer grain sizes However, materials produced through this method often display anisotropy in microstructure and mechanical properties, particularly along the Z direction, which is identified as the weakest point The dynamic properties of these materials are significantly affected by defects such as macroscopic voids, microporosity, and surface finish imperfections Nevertheless, with appropriate processing techniques like hot isostatic pressing and finish machining, additive manufactured alloys can demonstrate superior fatigue properties compared to their wrought counterparts.

Potential Far-Reaching Applications of Additive Manufacturing

Additive manufacturing processes have been effectively utilized across diverse industries, including aerospace, automotive, biomedical, energy conversion, consumer products, and sporting goods This field is illustrated by a tree model, which highlights the various feasible additive manufacturing processes at its base, while the trunk symbolizes the research and development efforts stemming from these processes The branches represent the direct outcomes and advantages resulting from these initiatives As research and development continue to advance rapidly, new applications and their associated benefits are anticipated to expand and gain increased attention over time.

Selective Laser Sintering Fused Deposition Modeling

Additive manufacturing has seen significant growth in recent years, driven by advancements in techniques and approvals for various applications Initially utilized for creating specialized tools for plastic injection molding, it has now expanded to produce a wide range of products, including medical implants, orthopedic and dental parts, hearing aids, forming tools, aerospace components, and military and automotive parts This diverse application highlights the evolving landscape of additive manufacturing and its increasing importance across multiple industries.

Current research is increasingly centered on biomedical applications, particularly the development of living tissues, while also exploring diverse fields such as electronics, art, jewelry, commercial lighting, videogame avatars, and engineered foods.

Aerospace components often feature complex geometries and are made from advanced materials like titanium alloys, nickel-based superalloys, specialty steels, ultra-high-temperature ceramics, and metal-matrix composites, which can be challenging to manufacture using traditional techniques Given the small production runs typical in the aerospace industry, additive manufacturing emerges as a suitable solution BAE Systems has successfully approved an entirely additive manufactured replacement part—a plastic window breather pipe for their 146 regional jets Similarly, Optomec, Inc has utilized the LENS process to create intricate metal components for satellites, helicopters, and jet engines Additionally, Arup, Inc has pioneered a 3D printing technique for structural steel elements, aiming to reduce energy consumption, costs, and waste in construction compared to traditional laser sintering methods.

Research at General Electric Aviation’s Additive Manufacturing Technology Center in Cincinnati, OH, has resulted in significant advancements in design, prompting increased investments in additive manufacturing technologies This innovative research focused on creating fuel nozzles through additive manufacturing techniques, ultimately leading to the establishment of a high-volume additive manufacturing facility in Auburn, AL.

A recent collaborative study by NASA’s Jet Propulsion Laboratory, the California Institute of Technology, and Pennsylvania State University has led to an innovative technique for creating gradient metal objects This method enables the design and manufacturing of parts with varying metal compositions tailored to specific requirements.

A custom 3D printer developed by Made-in-Space will be sent to the International Space Station to fabricate essential tools and components for space missions After successfully completing flight certification and acceptance testing in 2014, NASA engineers aim to demonstrate the printer's ability to produce components in space that match the quality of those made on Earth.

Optomec, Inc has effectively utilized LENS 3D printing technology, collaborating with top aerospace companies to create a reliable and cost-efficient alternative to traditional repair methods like manual welding The LENS process excels in adding metal to various existing substrates of nearly any 3D shape, making it ideal for repair operations In 2013, the European Space Agency, alongside industrial partners, confirmed the feasibility of 3D printing with lunar materials, evaluating radiation shielding from simulated lunar regolith, which will inform future designs They are also exploring a method that uses concentrated sunlight to melt regolith, eliminating the need for a binding liquid Each advancement in this research brings us closer to the reality of lunar colonization.

Additive manufacturing is revolutionizing the automotive industry by streamlining the design and development of components, significantly reducing both manufacturing and product costs This technology is particularly beneficial for producing small quantities of complex structural and functional parts, such as engine exhausts and braking systems, for luxury and low-volume vehicles In motorsports, where lightweight alloys like titanium and aluminum are essential, additive manufacturing effectively replaces traditional sand-casting and die-casting methods, allowing for the creation of intricate components that meet the high-performance demands of racing vehicles.

Local Motors, based in Phoenix, AZ, has successfully 3D printed a fully functional vehicle named the Strati, showcased at the 2014 International Manufacturing Technology Show The innovative printing process took 44 hours and was part of a design challenge that attracted over 200 participants from more than 30 countries This groundbreaking achievement marks the first instance of a car's main components being printed in one piece through direct digital manufacturing Following the printing, the Strati required an additional day for milling and two days for assembly, culminating in a total build time of five days Local Motors is rapidly establishing itself in the 3D printed automotive industry.

German electric vehicle manufacturer Street Scooter has successfully developed a prototype of its C16, utilizing the Stratasys Object1000 3D production system for its exterior components The 3D printed elements include front and back panels, door panels, bumper systems, side skirts, wheel arches, lamp masks, and various smaller interior parts While the final production model will incorporate more conventional manufacturing techniques, the 3D printing method enabled the prototype to be built cost-effectively within a 12-month timeframe Remarkably, the 3D printed car demonstrated performance in rigorous testing environments comparable to that of traditionally manufactured vehicles.

In the biomedical field, several recent applications have enabled the use of additive manufacturing for the fabrication of (1) custom-shaped orthopedic prostheses and implants, (2) medical devices,

(3) biological chips, (4) skull and jaw implants, (5) custom-molded mouthpieces for individuals suffering from sleep apnea, (6) tissue scaffolds, (7) living constructs, (8) drug-screening models,

The integration of 3D printing in spinal fusion surgery offers the advantage of creating customized implants tailored to individual patient anatomies Recently, Medicrea, an orthopedic implant manufacturer from Neyron, France, utilized advanced software and imaging techniques to develop a polymeric spine cage designed to fit seamlessly with a patient’s vertebral plates Although the process is currently patent pending, Medicrea is optimistic that this innovation will lead to further advancements in implantable devices that can either replace or support damaged spinal components Additionally, the ambition to create living tissues and organs through a scaffoldless technique using printed living cells was achieved in 2013, marking a significant milestone in the field of bioprinting.

1 Preprocessing—Creating tissue-specific or organ-specific CAD models for each patient using CT scan data

2 Processing—Using any of the viable additive manufacturing processes to deposit living cells onto 3D biological constructs

3 Postprocessing—Incubating printed tissues or organs to encourage both tissue fusion and maturation

Additive manufacturing has emerged as a transformative technology in the prosthetics industry, enabling the design and production of lightweight, cost-effective robotic components like hands and wrists This innovation allows for the consolidation of intricate assemblies into a single functional unit, enhancing both efficiency and usability.

Brightwake Limited, based in Nottinghamshire, U.K., has developed the Hemosep, a blood recycling machine created using the Stratasys Dimension 1200es 3D printer This innovative device recovers blood lost during open-heart or major trauma surgeries for autotransfusion back into the patient, minimizing the need for donor blood and reducing transfusion reaction risks The prototype features several 3D-printed components, including its main filtration and cooling systems Clinical trials conducted on over 100 open-heart surgeries in Turkey demonstrated Hemosep's effectiveness in significantly lowering blood transfusion requirements, highlighting the impactful role of 3D printing in the medical field.

3D printing techniques have revolutionized the transition from concept to functional prototype, enabling companies to innovate faster and more accurately than traditional methods Stratasys has launched a new 3D printer specifically designed for dental applications, setting a new standard for the prototyping and development of dental products and devices Additionally, the company is collaborating with suppliers to create integrated scanners for producing crowns, bridges, and veneers This advanced 3D printing technology aims to minimize patient time in the dental chair, enhancing the overall experience of dental procedures while also reducing costs.

Emergence and Use of Additive Manufacturing in Space

Both NASA and the U.S Air Force have explored opportunities to use additive manufacturing in space because it offers the following two capabilities:

1 Reducing the volume of launch vehicles when compared to equivalent spacecraft

2 Tailoring launch vehicles that deliver materials to orbit

Both of these factors can improve the economics related to launching, and additive manufacturing can also do the following: 115

1 Contribute to the design and manufacture of new materials and novel parts that can func- tion well in zero gravity but not necessarily in a terrestrial environment.

2 Transform operations and logistics planning due to the ability to launch a broad category of materials that can be used for the in situ manufacture of a range of parts offering a wide variety of functionality.

3 Contribute to the development of space hardware and robotic systems that will allow small spacecraft to be fully manufactured in space to suit specific needs.

To a large extent, the overall pace of implementation of the different additive manufacturing technologies will depend on the following:

1 Development of new engineering and testing protocols

2 Evaluation and approval of the protocols by professional organizations

3 Emergence of new engineering and management opportunities in both the aerospace industry and government

Additive manufacturing (AM) designs, derived from innovative materials and processes, must demonstrate durability and safety for their intended applications The integration of AM in space operations is expected to evolve over several decades, allowing for extensive study and evaluation of various techniques for hardware production Currently, only a few AM methods are sufficiently developed for producing aircraft and aerospace components on Earth, resulting in limited and primarily experimental applications of additive manufacturing in space.

1.10.1 p otential u SeR R equiReMentS and a nticipated t echnologieS

The National Aeronautics and Space Administration (NASA) is exploring additive manufacturing to innovate aeronautical technologies and enhance mission cost-effectiveness Similarly, the U.S Air Force employs additive manufacturing to operate and maintain a fleet of 55 spacecraft across five locations, demonstrating its practical applications in aerospace operations.

The Air Force is prioritizing the development of new systems to ensure space superiority, where the cost and speed of innovation are vital for maintaining a competitive edge against adversaries Additive manufacturing plays a significant role in this effort, as aerospace companies are exploring its potential to reduce tooling costs and serve as an effective production method for essential aircraft components.

1.10.2 g Round -b aSed a dditive M anuFactuRing FoR S pace

In 2011, Lockheed Martin utilized additive manufacturing for microwave communication brackets on NASA's Juno spacecraft, which is on a mission to Jupiter This innovation has prompted other companies to explore additive manufacturing for spacecraft products to reduce both time and costs Aerojet Rocketdyne, based in Sacramento, CA, successfully built and tested a rocket engine injector using additive manufacturing and now offers four space-qualified thruster systems produced through this method In 2012, Aurora Flight Sciences from Manassas, VA, developed and tested a thermoplastic drone system using fused deposition modeling on a commercial 3D printer, allowing for innovative aerodynamic designs and structural arrangements not feasible with traditional construction methods.

At the Jet Propulsion Laboratory in Pasadena, CA, researchers are pioneering the use of additive manufacturing to produce metal objects with tailored compositional gradients and localized properties This innovative approach enables the creation of material combinations and compositions that were previously impossible to achieve.

Ongoing research aims to create advanced hybrid additive manufacturing systems that integrate additive manufacturing machines with direct-write technologies and other manufacturing methods This innovative approach allows for the embedding of electronic components and circuitry in three dimensions during fabrication Significant efforts in the additive manufacturing sector are dedicated to developing machines that can apply additive materials to existing metallic and other substrates This capability promises substantial time savings in constructing complex structures by utilizing pre-manufactured items as a foundation.

The first CubeSat, conceived by students from California Polytechnic State University and Stanford University, was launched in 2003 on a Russian rocket Since then, over 100 of these compact satellites, each measuring 10 cm on each side, have been deployed into orbit for various technical applications.

Additive Manufacturing and Its Impact on Education

Educating the public about additive manufacturing empowers individuals to realize their dreams and democratizes the manufacturing process By disseminating this technology to potential end users, we create new opportunities for innovation Formal education in additive manufacturing has been incorporated into academic curricula across various educational levels, with rapid prototyping being a key component of manufacturing engineering courses at several universities Additionally, rapid prototyping is covered in traditional manufacturing textbooks, highlighting its importance in modern engineering education.

The article "Processes for Engineering Materials, 114" offers essential insights into the foundational concepts of additive manufacturing There is a noticeable increase in the availability of additive manufacturing courses at both undergraduate and graduate levels, reflecting the growing interest and demand in this field.

1 The “Solid Freeform Fabrication” course at the University of Texas in Austin

2 The “Rapid Prototyping in Engineering” course at the Georgia Institute of Technology in Atlanta

Community colleges play a crucial role in introducing students to the exciting field of additive manufacturing by offering courses that highlight the latest trends and developments The National Science Foundation's Advanced Technological Education (ATE) initiative supports two-year colleges through its Technician Education in Additive Manufacturing (TEAM) program, fostering the creation of relevant academic curricula ATE centers in Washington and California are dedicated to developing competencies and curricula that can serve as models for future program expansion However, access to essential educational materials, such as books and instructional guides for additive manufacturing courses and laboratory activities, remains limited at many educational institutions.

The Defense Advanced Research Projects Agency (DARPA) has launched the Manufacturing Experimentation and Outreach (MENTOR) program, a secondary-level education initiative that introduces additive manufacturing to high schools through 3D printing technology As part of DARPA's Adaptive Vehicle Make portfolio, the MENTOR program aims to expose emerging designers and innovators to foundry-style digital manufacturing principles through design challenges and competitions By providing 3D printers to high schools, the program seeks to revolutionize the design, verification, and manufacturing of complex defense systems and vehicles Having successfully completed its initial phase, the MENTOR program is expected to expand its reach over the next several years, promoting digital manufacturing education at the secondary level.

Various online resources provide accessible education and training in additive manufacturing, with MakerSpace emerging as a key platform This online community integrates manufacturing equipment, education, and collaboration, empowering members to design, prototype, and create manufactured parts MakerSpace symbolizes the democratization of design, engineering, and fabrication, fostering significant national projects Its goal is to explore low-cost initiatives to expand into community centers and schools, promoting the integration of design and collaboration tools for more economical physical workspaces.

A number of additive manufacturing course textbooks and reference books have been published by researchers working in the field Two notable ones are Additive Manufacturing Technologies:

Rapid Prototyping to Direct Digital Manufacturing 111 and Understanding Additive Manufacturing:

Rapid Prototyping, Rapid Tooling, Rapid Manufacturing 134 These books attempt to

Provide a comprehensive overview of additive manufacturing technologies along with descriptions of the support technologies, such as software systems and post-processing approaches.

Discuss a wide variety of both new and emerging applications, such as microscale additive manufacturing, medical applications, direct write electronics, and direct digital manufacturing of end-use components.

Introduce and provide a systematic solution for the selection and design of additive manufacturing processes.

Impact on Well-Being and Health

Since the end of World War II, easy access to vaccines, enhanced medicine availability, and advancements in surgical and therapeutic techniques have significantly improved global quality of life This progress has led to reduced mortality rates and increased life expectancy in both developed and developing countries As a result, the global population is steadily rising, with a growing aging demographic.

In 2006, approximately 500 million people worldwide were aged 65 and older, a figure expected to reach 1 billion by 2030 This demographic shift is placing significant pressure on government budgets globally, with individuals over 65 accounting for 32% to 42% of total healthcare expenditures, despite representing only 12% to 18% of the population Addressing the healthcare needs of this aging population poses critical challenges, necessitating the development of high-quality, economically efficient care aimed at enhancing overall well-being The current focus on personalized healthcare, which tailors treatment to individual patient characteristics and needs, is essential, particularly for long-term care of the elderly Additive manufacturing is emerging as a vital technology in this field, enabling the production of customized surgical implants and assistive devices that significantly improve health outcomes for the aging population.

Additive manufacturing is increasingly utilized for creating both solid and resorbable surgical implants, addressing the rising demand in the medical field For instance, in 2001, chin augmentation surgeries surged by 70%, with over 20,000 procedures performed in the United States, while lip and cheek augmentation surgeries saw increases of 49% and 47%, respectively Additionally, computed tomography enables the collection of patient data, facilitating the design of custom surgical implants tailored to individual needs.

Using reverse engineering, a precise model of the necessary implant is created, enabling the production of customized implants tailored to the patient's needs with suitable materials This method yields accurate and aesthetically pleasing implants while significantly reducing the design cycle and delivery time for custom surgical implants Additive manufacturing is utilized for various custom implants, including skull, knee, elbow, and hip joints, with dentistry being the most prevalent application area.

Additive manufacturing has revolutionized various industries, offering a range of commercial dentistry products and significantly enhancing the production of hearing aids In the realm of occupational safety and health, it has enabled the creation of custom-fit safety equipment, including helmets and protective clothing, designed to protect athletes, construction workers, firefighters, and police officers from potential hazards This innovative approach ensures that safety gear provides optimal protection while maintaining comfort, allowing users to perform at their best A notable project in a UK university focused on developing tailored protective sports garments, taking into account individual size and shape variations, resulting in seamless, one-piece designs that fit the body perfectly.

Additive Manufacturing Standards

The American Society for Testing and Materials (ASTM) is the global leader in developing and publishing international technical standards, with over 12,000 standards established to enhance product safety, quality, market access, and consumer confidence Alongside ASTM, the International Organization for Standardization (ISO) also plays a crucial role in standard development ASTM standards are collaboratively created by ASTM Committee F42 141 and ISO Technical Committee 261, focusing on essential areas such as terminology, processes and materials, and test methods.

The complexity of additive manufacturing has led to the identification of six key areas concerning raw materials, processes, equipment, and finished products To address these challenges, ASTM and ISO are prioritizing the investigation of critical concerns with the aim of establishing relevant standards for the industry.

1 Methods for qualification and certification

3 Test methods for the characterization of raw materials

4 Test methods to determine the mechanical properties of finished additive manufacturing parts and components

6 Standard protocols for round-robin testing

8 Requirements for purchased additive manufacturing parts

The widespread adoption of additive manufacturing in engineering and product development hinges on the establishment and acceptance of standards by ASTM, ISO, and manufacturing organizations Currently, existing standards fall short of promoting additive manufacturing as a fully recognized and accepted manufacturing process.

Concluding Remarks: The Future of Additive Manufacturing

Additive manufacturing, often dubbed the "third industrial revolution," offers substantial benefits through rapid and accurate production while also promoting positive environmental effects To match and surpass the benchmarks established by conventional manufacturing methods—particularly for vital structural applications—ongoing enhancements and thorough quantification studies are crucial A detailed investigation is required to systematically assess the static, dynamic, and high-temperature characteristics of materials produced through additive manufacturing, focusing on key objectives.

Identifying process–microstructure–property relationships

Studies in additive manufacturing enable manufacturers to optimize materials and techniques while developing effective product inspection methods Recent research has led to the production of critical components, including turbine blades, medical devices, and complex structural parts Innovative fabricators are now creating 3D-printed functional items such as clocks, guns, robots, and even components for 3D printers A significant emerging trend in additive manufacturing is its increasing application for personal consumer use.

1 ASTM (2010) Standard Terminology for Additive Manufacturing Technologies, F2792-12a ASTM International, West Conshohocken, PA.

2 Levy, G.N., Schindel, R., and Kruth, J.P (2003) Rapid manufacturing and rapid tooling with layer manufacturing (LM) technologies: state of the art and future perspectives CIRP Ann Manuf Technol., 52: 589–609.

3 Kruth, J.P., Leu, M.C., and Nakagawa, T (1998) Progress in additive manufacturing and rapid prototyping CIRP Ann Manuf Technol., 47: 525–540.

4 Gero, J.S (1995) Recent advances in computational models of creative design In: Design Research in the Netherlands (Oxman, R., Bax, T., and Achten, H., Eds.), pp 56–57 ETH, Eindhoven.

5 Chu, C., Graf, G., and Rosen, D.W (2008) Design for additive manufacturing of cellular structures

6 Kruth, J.P (1991) Material ingress manufacturing by rapid prototyping techniques CIRP Ann Manuf

7 Flowers, J and Moniz, M (2002) Rapid prototyping in technology education Technol Transfer, 62(3): 7.

8 Wohlers, T (2012) Additive manufacturing advances Manuf Eng., 148(4): 55–56.

9 Bourell, D.L., Beaman, Jr., J.J., Leu, M.C., and Rosen, D.W (2009) A Brief History of Additive Manufacturing and the 2009 Roadmap for Additive Manufacturing: Looking Back and Looking Ahead, paper presented at RapidTech 2009, Erfurt, Germany, May 26–27.

10 Lou, A and Grosvenor, C (2012) Selective Laser Sintering: Birth of Industry University of Texas, Austin.

11 Jacobs, P.F (1992) Rapid Prototyping & Manufacturing: Fundamentals of StereoLithography Society of Manufacturing Engineers, Dearborn, MI.

12 Pham, D.T and Dimov, S.S (2001) Rapid Manufacturing: The Technologies and Applications of Rapid

Prototyping and Rapid Tooling Springer Verlag, New York.

13 Hauser, C., Sutcliffe, C.S., Egan M., and Fox, P (2005) Spiral Growth Manufacturing (SGM): A Continuous Additive Manufacturing Technology for Processing Metal Powder by Selective Laser Melting, paper presented at 16th Solid Freeform Fabrication Symposium, Austin, TX, August 13.

14 Herderick, E (2011) Additive Manufacturing of Metals: A Review, paper presented at Materials Science and Technology (MS&T) 2011, Columbus, OH, October 16–20.

15 Scott, J., Gupta, N., Weber, C., Newsome, S., Wohlers, T., and Caffrey, T (2012) Additive Manufacturing

Status and Opportunities IDA, Science and Technology Policy Institute, Washington DC.

16 Vilaro, T., Colin, C., and Bartout, J.D (2011) As-fabricated and heat-treated microstructures of the Ti-6Al-4V alloy processed by selective laser melting Metall Mater Trans A, 42A: 3190–3199.

17 Wang, F., Williams, S.W., Colegrove, W.P., and Antonysamy, A.A (2013) Microstructure and mechanical properties of wire and arc additive manufactured Ti-6Al-4V Metall Mater Trans A, 44A: 968–977.

18 Hon, K.B.B., Han, C., and Edwardson, S.P (2006) Investigation of new scanning pattern for stereolithography Annals CIRP, 55(1): 217–220.

19 Wong, K.V and Hernandez, A (2012) A review of additive manufacturing ISRN Mech Eng., 2012: 1–10.

20 Frazier, W.E (2014) Metal additive manufacturing: a review J Mater Eng Perform., 23: 1917–1928.

21 Milewski, J.O., Dickerson, P.G., Nemec, R.B., Lewis, G.K., and Fonseca, J.C (1999) Application of a manufacturing model for optimization of additive processing of Inconel Alloy 690 J Mater Process

22 Akula, S and Karunakaran, K.P (2006) Hybrid adaptive layer manufacturing: an intelligent asset of direct metal rapid tooling process Robot Comput Integr Manuf., 22: 113–123.

23 Santua, E.C., Shiomi, M., Osakada, K., and Laoui, T (2006) Rapid manufacturing of metal components by laser forming Int J Machine Tools Manuf., 46: 1459–1468.

24 Roberts, I.A., Eng, C.J., Esterlein, R., Stanford, M., and Mynorts, D.J (2009) A three-dimensional finite element analysis of the temperature field during laser melting of metal powders in additive layer manufacturing, Int J Machine Tools Manuf., 49: 916–923.

25 Baufeld, B., van der Biest, O., and Gault, R (2010) Additive manufacturing of Ti-6Al-4V components by shaped metal deposition: microstructure and mechanical properties Mater Des., 31: S106–S111.

26 Levy, G.N (2012) The role and future of the laser technology in additive manufacturing environment.

27 Sriraman, M.R., Babu, S.S., and Short, M (2010) Bonding characteristics during very high power ultrasonic additive manufacturing of copper Scripta Mater., 62: 560–563.

28 Ramirez, D.A., Murr, L.E., Martinez, E., Hernandez, D.H., Martinez, J.L., Machado, B.I., Medina, F., Frigola, P., and Wicker, R.B (2011) Novel precipitate microstructural architecture developed in the fabrication of solid copper components by additive manufacturing using electron beam melting, Acta Mater., 59: 4088–4099.

29 Bibb, R., Thompson, D., and Winder, J (2011) Computed tomography characterization of additive manufacturing materials Med Eng Phys., 33: 590–596.

30 Baufeld, B., Brandl, E., and van der Biest, O (2011) Wire-based additive layer manufacturing: comparison of microstructure and mechanical properties of Ti-6Al-4V fabricated by laser beam deposition J

31 Zaeh, M.F and Ott, M (2011) Investigations on heat regulation of additive manufacturing processes for metal structures CIRP Ann Manuf Technol., 60: 259–262.

32 Martina, F., Mehnen, J., Williams, S.W., Colegrove, P., and Wang, T (2012) Investigation of the benefits of plasma deposition for additive layer manufacture of Ti-6Al-4V J Mater Process Technol., 212: 1377–1386.

33 Brandl, E., Heckenberger, U., Holzinger, V., and Buchbinder, D (2012) Additive manufactured AlSi10Mg samples using selective laser melting: microstructure, high cycle fatigue and fracture behavior Mater Des., 34: 159–169.

34 Friel, R.J and Harrys, R.A (2013) Ultrasonic additive manufacturing: a hybrid production process for novel functional products Proc CIRP, 6: 35–40.

35 Suter, M., Weingartner, E., and Wegener, K (2012) MHD print-head for additive manufacturing of metals Proc CIRP, 2: 102–106.

36 Boisselier, D and Sankare, S (2012) Influence of powder characteristics in laser direct metal deposition of SS316L for metallic parts manufacturing, Phys Proc., 39: 455–463.

37 Vayre, B., Vignat, F., and Villeneuve, F (2012) Designing for additive manufacturing, Proc CIRP, 3: 632–637.

38 Foster, D.R., Daoino, M.J., and Babu, S.S (2012) Elastic constants of ultrasonic additive manufactured

39 Niendorf, T and Brenne, F (2013) Steel showing twinning induced plasticity processed by selective laser melting: an additive manufactured high performance material Mater Charact., 85: 57–63.

40 Cooper, D.E., Blundell., N., Maggs, S., and Gibbons, G.J (2013) Additive layer manufacturing of Inconel 625 metal matrix composites reinforcement material evaluation J Mater Process Technol., 213: 2191–2200.

41 Kumar, V and Dutta, D (1997) An assessment of data formats for layered manufacturing Adv Eng

42 ASTM (2011) Standard Specification for Additive Manufacturing File Format, F2915-11 ASTM International, West Conshohocken, PA.

43 Juster, N.P and Childs, T.H.C (1994) A comparison of rapid prototyping processes In: Proceedings of the Third European Conference on Rapid Prototyping and Manufacturing, University of Nottingham,

44 Chua, C.K., Choi, S.M., and Wong, T.S (1998) A study of state-of-the art rapid prototyping technologies Int J Adv Manuf Technol., 14(2): 146–152.

45 Jacobs, P.F (1992) Rapid Prototyping & Manufacturing: Fundamentals of StereoLithography Society of Manufacturing Engineering, Dearborn, MI.

46 ASTM (2014) Standard Specification for Additive Manufacturing Titanium-6 Aluminum-4 Vanadium with Powder Bed Fusion, F2924 ASTM International, West Conshohocken, PA.

47 Ashley, S (1991) Rapid prototyping systems Mech Eng., 113(4): 34.

48 Cooper, K (2001) Rapid Prototying Technology Marcel Dekker, New York.

49 Kochan, A (1997) Features rapid growth for rapid prototyping Assembly Automation, 17(3): 215–217.

50 Noorani, R (2006) Rapid Prototyping: Principles and Applications John Wiley & Sons, New York.

51 Kruth, P.P (1991) Material incress manufacturing by rapid prototyping techniques CIRP Ann Manuf

52 Halloran, J.W., Tomeckova, V., and Gentry, S (2011) Photo-polymerization of powder suspensions for shaping ceramic materials J Eur Ceramic Soc., 31(14): 2613–2619.

53 Pham, D.T and Ji, C (2000) Design for stereolithography Proc Inst Mech Eng., 214(5): 635–640.

54 Kim, H., Jae Won, C., and Wicker, R (2010) Scheduling and process planning for multiple material stereolithography Rapid Prototyping J., 16(4): 232–240.

55 Pham, D.T and Gault, R.S (1998) A comparison of rapid prototyping technologies Int J Machine Tool

56 Feygin, M and Hsieh, B (1991) Laminated Object Manufacturing (LOM): A Simpler Process, paper presented at Second Freeform Fabrication Symposium, Austin, TX, August 6–8.

57 Skelton, J (2008) Fused deposition modeling 3D Printers and 3D-Printing Technologies Almanac, February 8, http://3d-print.blogspot.com/2008.

58 Kamrani, A.K and Nasr, E.S (2010) Engineering Design and Rapid Prototyping Springer, New York.

59 Sachs, E., Cima, M., and Cornie, J (1990) Three-dimensional printing: rapid tooling and prototypes directly from a CAD model CIRL Ann Manuf Technol., 39: 201–204.

60 Miller, R (2014) Additive manufacturing (3D printing): past, present and future Indust Heating, May: 39–41.

61 Rooks, A (2014) Is it a.m for AM? Cutting Tool Eng., February: 8.

62 Hock, L (2014) 3-D printing: a new manufacturing staple R&D Mag., April.

63 Beaman, J.J., Barlow, J.W., Bourell, D.L., Crawford, R.H., Marcus H.L., and McAlea, K.P (1996) Solid

Freeform Fabrication: A New Direction in Manufacturing Springer, New York.

64 Deckard, C and Beaman, J.J (1988) Process and control: issues in selective laser sintering ASME PED, 33: 191–197.

65 Hwa Hsing, T., Ming Lu, C., and Hsiao Chuan, Y (2011) Slurry-based selective laser sintering of polymer- coated ceramic powders to fabricate high strength alumina parts J Eur Ceramic Soc., 31(8): 1383–1388.

66 Salmoria, G.V., Paggi, R.A., Lago, A., and Beal, V.E (2011) Microstructure and mechanical characterization of PA12/MWCNTs nanocomposite manufactured by selective laser sintering Polym Testing, 30(6): 611–615.

67 Skavko, D and Matic, K (2010) Selective laser sintering of composite materials technologies Ann

68 Mrudge, R.P and Wald, N.R (2007) Laser engineered net shaping advances in additive manufacturing and repair Weld J., 86: 44–48.

69 Griffith, M.L., Schlierger, M.E., and Harwell, L.D (1999) Understanding thermal behavior in the LENS process Mater Des., 20: 107–113.

70 Xiong, Y (2009) Investigation of the Laser Engineered Net Shaping Process for Nanostructured Cermets, doctoral dissertation, University of California, Davis.

71 Balkla, V.K., Bose S., and Bandyopadhyay, A (2008) Processing of bulk alumina ceramics using laser engineered net shaping Int J Appl Ceramic Technol., 5(3): 234–242.

72 Liao, Y.S., Li, H.C., and Chiu, Y.Y (2006) Study of laminated object manufacturing with separtely applied heating and pressing Int J Adv Manuf Technol., 27(7–8): 703–708.

73 Murr, L.E., Gaytan, S., and Ramirez, D (2012) Metal fabrication by additive manufacturing using laser and electron beam melting technologies J Mater Sci Technol., 28(1): 1–14.

74 Semetay, C (2007) Laser Engineered Net Shaping: Modeling Using Welding Simulation Concepts, doctoral dissertation, Lehigh University, Bethlehem, PA.

75 Zhai, Y and Lados, D.A (2012) WPI Bi-annual Progress Report Integrative Materials Design Center (iMdc), Worcester, MA.

76 Castle Island (2013) Worldwide Guide to Rapid Prototyping: Laser Sintering, http://www.additive3d. com/sls.htm.

77 Optomec (2014) LENS Technology, www.optomec.com/?s=lens+technology.

78 Castle Island (2013) Direct Additive Fabrication of Metal Parts and Injection Molds, http://www.addi- tive3d.com/tl_221a.htm.

79 Castle Island (2013) Laser Powder Forming, http://www.additive3d.com/lens.htm.

80 Brice, C.A and Henn, D.A (2002) Rapid Prototyping and Freeform Fabrication Via Electron Beam Welding Deposition, paper presented at International Institute of Welding Conference, Copenhagen, Denmark, June 26–28.

81 Taminger, K.M and Hafley, R.A (2006) Electron Beam Freeform Fabrication for Cost Effective Near- Net Shape Manufacturing, paper presented at NATO AVT-139 Specialists Meeting on Cost Effective Manufacture Via Net Shape Processing, Amsterdam, May 15–19.

82 Gibson, I., Rosen, D.W., and Stucker, B (2010) Additive Manufacturing Technologies: Rapid Prototyping to Direct Digital Manufacturing Springer, New York.

83 Villafuerte, J (2014) Considering cold spray for additive manufacturing Adv Mater Process., May: 50–52.

84 Xue, L and Islam, M.U (2000) Free form laser consolidation for producing metallurgically sound and functional components J Laser Appl., 12(4): 160–165.

85 Scott, J., Gupta, N., Weber, C., Newsome, S., Wohlers, T., and Caffrey, T (2012) Additive Manufacturing

Status and Opportunities Science and Technology Policy Institute, Washington, DC.

86 Anon (2012) The third industrial revolution Economist, April 21, http://www.economist.com/node/ 21553017.

87 Jackson, T.R., Liu, H., Partrikalakis, N.M., Sachs, E.M., and Cima, M.J (1999) Modeling and designing functionally graded material components for fabrication with local composition control Mater Des., 20(2–3): 63–75.

88 Guo, N and Leu, M.C (2013) Additive manufacturing technology: applications and research needs

89 Liu, F., Slattery, K., Kinsella, M., Newkirk, J., Chou, H.N., and Landers, R (2007) Applications of a hybrid manufacturing process for fabrication of metallic structures Rapid Prototyping J., 13(4): 236–244.

90 Wohlers, T.T (2014) 3D Printing and Additive Manufacturing State of the Industry, Annual Worldwide

Progress Report Wohlers Associates, Inc., Fort Collins, CO.

91 Wohlers Assoc (2014) Metal Additive Manufacturing Grows by Nearly 76% [press release], May 21, Wohlers Associates, Inc., Fort Collins, CO (http://wohlersassociates.com/press64.html).

92 NIST (2013) Measurement Science Roadmap for Metal-Based Additive Manufacturing National

Institute for Standards and Technology, Gaithersburg, MD.

93 Additive Manufacturing Consortium, http://ewi.org/additive-manufacturing-consortium/.

94 Zhai, Y and Lados, D.A (2012) Integrative Materials Design Center Biannual Progress Report Worcester Polytechnic Institute, Worcester, MA.

95 Murr, L.E., Gaytan, S.M., Ramirez, D.A., Martinez, E., Hernandez, J et al (2012) Metal fabrication by additive manufacturing using laser and electron beam melting technologies J Mater Sci Technol., 28(1): 1–14.

96 Amano, R.S and Rohatgi, P.K (2011) Laser engineered net shaping process for SAE 4140 low alloy steel Mater Sci Eng., 528(22–23): 6680–6693.

97 Wu, X., Liang, J., Mei, J., Mitchell, C., Goodwin, P.S., and Voice, W (2004) Microstructures of laser- deposited Ti-6Al-4V Mater Des., 25(2): 137–144.

98 Thijs, L., Verhaeghe, F., Craeghs, T., van Humbeeck, J., and Kruth, J.-P (2010) A study of the microstructural evolution during selective laser melting of Ti-6Al-4V Acta Mater., 58(9): 3303–3312.

99 Kempen, K., Yasa, E., Thijs, L., Kruth, J.-P., and van Humbeeck, J (2011) Microstructure and mechanical properties of selective laser melted 18Ni-300 steel Phys Proc., 12(1): 255–263.

100 Rangers, S (2012) Electron Beam Melting Versus Direct Metal Laser Sintering, paper presented at Midwest SAMPE’s Direct Part Manufacturing Workshop, Wright State University, Fairborn, OH, November 13–14.

101 Ramosoeu, M.K.E., Booysen, G., Ngoda T.N., and Chikwanda, H.K (2011) Mechanical Properties of Direct Laser Sintered Ti-6Al-4V, paper presented at Materials Science and Technology (MS&T) 2011, Columbus, OH, October 16–20.

In a study presented at the 27th Symposium of the International Committee on Aeronautical Fatigue in Jerusalem, Greitemeir et al (2013) explored the additive laser manufacturing processes for Ti-6Al-4V and Scalmalloy ©, focusing on their implications for fatigue and fracture behavior.

103 Murr, L.E., Martinez, E., Gaytan, S.M., Ramirez, D.A., Machado, B.I et al (2011) Microstructure and mechanical properties of a nickel base superalloy fabricated by electron beam melting Metall Trans A, 42: 3491–3508.

104 Baufeld, B (2012) Mechanical properties of Inconel 718 parts manufactured by shaped metal deposition J Mater Eng Perform., 21(7): 1416–1421.

105 Ganesh, P., Kaul, R., Paul, C.P., Tiwari, P., Rai, S.K., Prasad, R.C., and Kukreja, L.M (2010) Fatigue and fracture toughness characteristics of laser rapid manufactured Inconel 625 structures Mater Sci Eng., 527(29–30): 7490–7497.

106 Chlebus, E., Kuznicka, B., Kurzynowski, T., and Dyba, B (2011) Microstructure and mechanical behavior of Ti-6Al-7Nb alloy produced by selective laser melting Mater Charact., 62(5): 488–495.

107 Blackwell, P.L and Wisbey, A.J (2005) Laser-aided manufacturing technologies: their application to the near-net shape forming of a high-strength titanium alloy Mater Proc Technol., 170: 268.

108 Vrancken, B., Thijs, L., and Kruth, J.P (2012) Heat treatment of Ti6Al4V produced by selective laser melting: microstructure and mechanical properties J Alloys Compd., 541: 177.

109 Martukanitz, R., Simpson, T., and The Center for Innovative Materials Processing through Direct Digital Deposition (2013) Brief at the Technology Showcase ARL Information Center, Penn State, State College, PA.

110 Bourell, D.L., Leu, M.C., and Rosen, D (2009) Roadmap for Additive Manufacturing: Identifying the

Future of Freeform Processing University of Texas, Austin.

111 Gibson, I., Rosen, D.W., and Stucker, B (2010) Additive Manufacturing Technologies: Rapid Prototyping to Direct Digital Manufacturing Springer, New York.

112 Optomec, http://www.optomec.com/.

113 Hofmann, D.C., Borgonia, J.P.C., Dillon, R.P., Suh, E.J., Mulder, J.L., and Gardner, P.B (2013)

Applications for Gradient Metal Alloys Fabricated Using Additive Manufacturing, NASA Technical

Brief Jet Propulsion Laboratory, National Aeronautics and Space Administration, Pasadena, CA.

114 Kalpakjian, S and Schmid, S.R (2008) Manufacturing Processes for Engineering Materials, 5th ed Prentice Hall, Englewood Cliffs, NJ.

115 National Research Council (2011) 3D Printing in Space National Academies Press, Washington DC.

116 Coxworth, B (2014) Report on prototype electric car made with a 3D printer Stratasys, November 19.

117 Roberts, S., www.youtube.com/watch?vowikH7Z1.

118 Scott, J., Gupta, N., Weber, C., Newsome, S., Wohlers, T., and Caffrey, T (2012) Additive Manufacturing:

Status and Opportunities Science and Technology Policy Institute, Washington DC.

119 Hock, L (2014) 3D printing for blood recycling, medical developments Prod Des Dev., October 7, http://www.pddnet.com/articles/2014/10/3d-printing-blood-recycling-medical-developments.

120 Bullis, K (2014) EmTech: 3-D printing complex kidney components MIT Technol Rev., September 24, http://www.technologyreview.com/news/531106/emtech-3-d-printing-complex-kidney-components/.

121 Lavars, N (2014) 3D-printed syringe pumps could cut the cost of scientific research Gizmag, September

17, http://www.gizmag.com/3d-printed-syringe-pump-scientific-research/33863/.

122 Coxworth, B (2014) Organovo now selling tiny 3D printed human livers Gizmag, November 19, http:// www.gizmag.com/organovo-exvive3d-liver-models/34843/.

123 Lavars, N (2014) 3D printing helps build upper jaw prosthetic of cancer patient Gizmag, October 17, http://www.gizmag.com/3d-printing-upper-jaw-prosthetic-cancer/34303/.

124 Laird, J (2014) “Spinning” a solution for tracheal surgery Med Des., October 20, http://medicaldesign. com/prototyping/spinning-solution-tracheal-surgery.

125 Aurora Laboratories (2014) Metal 3D printer—yours for under US$5,000 Mater Today, October 9, http:// www.materialstoday.com/additive-manufacturing/news/metal-3d-printer-yours-for-under-us5000/.

126 Mraz, S (2014) Developing medical devices with 3D IM Machine Des., October 9, http://machinede- sign.com/3d-printing/developing-medical-devices-3d-im.

127 Anon (2014) Market trends: additive manufacturing on the rise Ceram Indust Mag., May 1, http:// www.ceramicindustry.com/articles/93901-market-trends-additive-manufacturing-on-the-rise.

122 McCormick, S (2012) Chin Surgery Skyrockets among Women and Men in All Age Groups [press release] American Society of Plastic Surgeons, Arlington Heights, IL (http://www/eurekalert.org/ pub_releases/2012-04).

128 Svensson, P (2014) The new family portrait? 3D-printed statue selfies Washington Times, October 9, http://www.washingtontimes.com/news/2014/oct/9/the-new-family-portrait-3d-printed-statue-selfies/.

129 Hock, L (2014) Scanning products into 3-D: 3-D scanning technology reduces costs and speeds up product development with new technology advancements R&D Mag., August 6, http://www.rdmag.com/ articles/2014/08/scanning-products-3-d.

130 Lavars, N (2014) Wasp’s 3D printers produce low-cost houses made from mud Gizmag, October 20, http://www.gizmag.com/wasp-3d-printers-house-mud/34340/.

131 Newman, J (2014) Rapid ready tech: could 3D printing save the US Postal Service? Desktop Eng., July

14, http://www.rapidreadytech.com/2014/07/could-3d-printing-save-the-us-postal-service/.

132 Leigh, S.J., Bradley, R.J., Purssell, C.P., Billson, D.R., and Hutchins, D.A (2012) A simple, low cost conductive composite material for 3D printing of electronic sensors PLoS ONE, 7(11): e49365.

133 Davis, S (2011) Construction of a CubeSat Using Additive Manufacturing, SAE Technical Paper 2011- 01-2568 SAE International, Warrensdale, PA.

134 Gebhardt, A (2012) Understanding Additive Manufacturing: Rapid Prototyping, Rapid Tooling, Rapid

Manufacturing Hanser Publications, Cincinnati, OH.

135 National Institute on Aging (2007) Why Population Aging Matters: A Global Perspective, Publ No 07-6134 National Institute on Aging, Bethesda, MD.

136 OECD (1996) Ageing in OECD Countries: A Critical Policy Challenge Organization for Economic Co-operation and Development, Paris.

137 Beattie, W (1998) Current challenges to providing personalized care in the long term care facility Int

J Health Care Qual Assur Inc Leadersh Health Serv., 11(2–3): i–v.

138 Ely, S (2009) Personalized medicine: individual care of cancer patients Trans Res., 154(6): 303–308

139 Huang, S., Liu, P., Mokasdar, A., and Hou, L (2013) Additive manufacturing and its societal impact Int

140 He, Y., Ye, M., and Wang, C (2006) A method in the design and fabrication of exact-fit customized implants based on sectional medical images and rapid prototyping technology Int J Adv Manuf

141 Picariello, P (2009) Committee F42 on Additive Manufacturing Technologies ASTM International, West Conshohocken, PA, http://www.astm.org/COMMITTEE/F42.htm.

Additive manufacturing enables the creation of intricate three-dimensional objects directly from computer models, allowing for complex internal and external geometries This research focuses on developing a groundbreaking additive manufacturing technology that can deposit shapes in free space without the need for support structures, thereby overcoming existing limitations in the field.

2.1 Introduction 502.2 Modeling Deposition of Tracks in Free Space 512.2.1 Experimental Apparatus 512.2.2 Classification of Results 522.2.3 Experimental Methodology 532.2.3.1 Effect of Varying Material Feed Rate 532.2.3.2 Effect of Varying Temperature 532.2.3.3 Effect of Varying Initial Volume of Material Fed 532.2.3.4 Effect of Varying Velocity 532.2.4 Results 542.2.4.1 Effect of Material Feed Rate 542.2.4.2 Effect of Varying Soldering Iron Temperature 542.2.4.3 Effect of Varying Initial Volume of Material Fed to Electrode 542.2.4.4 Effect of Varying Velocity 562.2.5 Discussion 562.3 Modeling Free Space Deposition 582.3.1 Experimental Methodology 602.3.1.1 Estimating the Track Profile 602.3.1.2 Effect of Initial Operating Settings on Track Taper 612.3.2 Results 612.3.2.1 Estimating the Track Profile 612.3.2.2 Effect of Initial Operating Conditions on Track Taper 622.3.3 Discussion 642.4 Conclusions 65Acknowledgments 68References 68 deposition in the x-y plane that most current technologies utilize The contribution of this research is the use of a heated tool as a temporary moving support structure during material solidification to deposit tracks in free space Notable results in free space track deposition were that the initial track diameter and volume affected the repeatability and quality of tracks The amount of material fed to the soldering iron before commencing deposition affected the taper of tracks At an initial volume of 7 mm 3 and an initial track diameter of 0.8 mm, none of the ten tracks deposited broke or showed taper > ~1° The maximum deposition velocity for free space track deposition using lead-free solder was limited to 1.5 mm s –1 Finite element modeling showed that the initial volume within the melt boundary, initial track radius, and distance between the soldering iron and the solidification front could be used to inform future experimental design Selection of initial operating settings may be used to produce tracks profiles with standard deviations < 30% of initial track width.

Additive manufacturing enables the creation of three-dimensional objects directly from computer designs by selectively depositing materials, allowing for intricate internal and external geometries However, conventional metal additive manufacturing techniques, particularly selective laser melting (SLM), face challenges in constructing overhanging structures with angles less than 40° to 45° from the horizontal without the use of fixed support structures These support structures are essential for maintaining stability during the solidification process and are typically removed afterward By supporting individual tracks during solidification, it becomes feasible to create overhanging features that extend into free space, which may eliminate the need for ongoing support after the initial solidification, thereby allowing for more versatile deposition methods.

The image in Figure 2.1 showcases track deposition in free space, featuring a manual construction of the word "Science" at the top, while the bottom displays various shapes undergoing the deposition process.

This study explores the use of a moving support structure in the solidification process, utilizing a soldering iron as both the heat source and the support Lead-free solder serves as the deposition material, with potential applications extending to higher melting point materials like stainless steel and titanium For additional insights on the deposition of these materials, refer to the works of Rangesh and O’Neill.

This research summary is organized into two key sections: the deposition of tracks in free space and the underlying theory of this process The first section examines the operating parameters that influence the repeatability and quality of free space tracks Meanwhile, the second section contrasts experimental results with a computer model of the molten track boundary, aiming to predict the behavior of free space track deposition in a broader context.

2.2 ModelIng deposItIon of trACKs In free spACe

The experimental setup, illustrated in Figure 2.2, features a soldering iron mounted on a FANUC LR Mate® 200iC robotic arm, allowing for horizontal or vertical positioning The wire feeder rollers are powered by a Trinamic PD1-013-32 stepper motor, ensuring precise control A 50-W Antex 660TC temperature-controlled soldering iron, equipped with a modified Antex B110660 tip, is utilized for the experiments, employing lead-free solder for enhanced environmental safety.

Mounting Holes to Attach Assembly to Robot

Clamp to Hold Soldering Iron

Guide Plate for Tin Alloy Wire

Tin Alloy Wire Wire Feeder Gears

Groove to Guide Tin Alloy Wire Vice to Hold Sample

Horizontal Track in Free Space

The experimental setup involves a six-axis robotic arm equipped with a soldering iron and wire feeder, which deposits lead-free solder tracks on a substrate The solder used is Sn3.5Ag0.5Cu with a 1 mm diameter and a melting point of 217°C, featuring a rosin flux core that enhances wetting properties by acting as a cleaning agent Research by Arenas and Acoff indicates that on a copper substrate, rosin-activated flux significantly lowers the contact angle of Sn3.8Ag0.7Cu, decreasing it from approximately 40° to 30° at 240°C, and further to 20° at 280°C.

Introduction

Additive manufacturing (AM) is a revolutionary layer-based fabrication technology that has become essential for various innovative applications across multiple industries Among its methods, electron beam melting (EBM) utilizes a high-energy electron beam to effectively melt and fuse powder, representing a cutting-edge advancement in AM.

The Electron Beam Melting (EBM) additive manufacturing process enables the production of full-density metallic parts directly from digital designs, garnering significant interest from aerospace, military, and biomedical sectors due to its unique advantages These include the ability to create complex geometries, rapid scanning speeds, and moderate operational costs Key research areas in EBM encompass material characterization, process modeling, and part accuracy The EBM process consists of powder spreading, preheating, and melting, where preheating lightly sinters the powder layer using a low-power electron beam at high speeds, thereby stabilizing the metal powder during melting and reducing thermal gradients Studies indicate that preheating enhances power density and scanning speed, supports down-facing surfaces, and minimizes energy consumption during melting However, there remains a lack of systematic research on the characteristics of preheated powder and its impact on the layer-building mechanism in EBM.

Ti-6Al-4V is a widely utilized alloy in Electron Beam Melting (EBM) additive manufacturing, characterized by a microstructure that includes a blend of α (hexagonal closed packed), β (body-centered cubic), and αʹ martensite phases The initial solidification process leads to a columnar prior β structure due to significant temperature gradients along the build direction Research by Safdar et al revealed typical Widmanstätten (α+β) formations within prior β grains, while Facchini et al highlighted that the predominant phase in EBM Ti-6Al-4V is α, with minimal β presence A comparative analysis by Christensen et al showed that EBM specimens exhibit fine acicular (β) and thin prior β grain boundaries, contrasting with the coarse acicular (α+β) and thick prior β grain boundaries found in cast specimens The α-lath thickness in EBM samples ranges from 1.4 to 2.1 μm The high cooling rates during solidification result in αʹ martensitic platelets, which enhance strength and hardness but reduce ductility Overall, EBM-produced Ti-6Al-4V displays a fine Widmanstätten (α+β) microstructure along with αʹ, influenced by the EBM process's thermal characteristics, including a small melt pool and rapid cooling Additionally, the layer-by-layer construction method in EBM raises important considerations regarding the effects of build heights and orientations on the microstructures of the final parts.

The parameters of the Electron Beam Melting (EBM) process significantly influence part quality, with studies indicating that variations in melt scan, beam current, and scan speed can lead to defects like porosity, which are linked to microstructure changes in the final product The electron beam scanning speed is particularly crucial, as research by Jamshidinia et al demonstrated that a speed of 1000 mm/s results in a much higher cooling rate compared to 100 mm/s and 500 mm/s Additionally, Bontha et al developed thermal process maps to predict solidification microstructures in wire-feed electron beam freeform fabrication, further emphasizing the importance of optimizing process parameters for improved outcomes.

Increasing the scanning speed in Electron Beam Melting (EBM) may significantly reduce the grain size of Ti-6Al-4V build parts Although numerous studies have been conducted to model and analyze EBM, the connection between scanning speed and the microstructure of EBM components remains inadequately understood.

In spite of many advantages and potential benefits of EBM AM, there exist several challenges for effective usage and widespread applications For example, a common process deficiency of EBM

AM is the delamination of build layers When the residual stresses exceed the binding abilities between the adjacent layers, layer delaminations occur and significantly degrade the part quality 3,22

In order to avoid EBM part defects, understanding the powder characteristics and parts microstructure is of great importance.

This study aimed to explore the characterizations of Ti-6Al-4V powder and the microstructures of parts produced through Electron Beam Melting (EBM) Additive Manufacturing (AM) Utilizing a commercial EBM system, both solid specimens and those with preheated powder were fabricated The research focused on the morphology, porosity, and size distribution of Ti-6Al-4V powder in the context of EBM AM Additionally, the microstructures of EBM-built Ti-6Al-4V parts were analyzed in relation to build height and orientation The study also examined how variations in scanning speed influenced microstructural characteristics, including phases and characteristic lengths Ultimately, the goal was to establish a correlation between metal powder characteristics, part microstructures, and the thermal processes involved in EBM.

Experimental Details

Pre-alloyed Ti-6Al-4V raw powder was used as the feedstock material The chemical composition is listed in Table 7.1. tAble 7.1

Chemical Analysis for ti-6Al-4v powder element

Source: Data from Gong X and Chou, K., in Proceedings of ASME 2013 International

Manufacturing Science and Engineering Conference/41st North American Manufacturing Research Conference, pp 1–8.

7.2.1.2 Machine, Material, and fabrication parameters and Conditions

The experimental specimens were fabricated based on designed part models and using an EBM

NASA’s Marshall Space Flight Center in Huntsville, AL, utilizes the Arcam S12 additive manufacturing system (AM) with Ti-6Al-4V powder, employing standard process parameters including a layer thickness of 70 micrometers During the preheating phase, the scan speed reaches approximately 10 m/s with a beam current of around 30 mA, aiming for a target preheat temperature of 730°C, maintained for about 5 seconds.

7.2.1.3 powder-bed and powder-enclosed samples

Two types of samples featuring sintered powder particles were created for microstructural analysis: powder-bed samples collected from the powder bed post-build and powder-enclosed samples, illustrated in Figure 7.1 Both the z-plane (scanning surface) and x-plane (side surface) were examined, as depicted in Figure 7.1A.

Samples for microstructural analysis were prepared using standard metallographic techniques, which included sectioning, mounting, and grinding with silicon carbide papers up to a grit size of 1000 They were then polished with diamond suspensions down to 0.5 micrometers For etching, Kroll's reagent, composed of 92 mL distilled water, 6 mL nitric acid, and 2 mL hydrofluoric acid, was applied The samples were immersed in the etching solution for approximately 30 seconds, rinsed with water, and air-dried The metallographic samples were subsequently examined using a Leitz optical microscope and a Philips XL-30 scanning electron microscope.

To investigate particle sizes, distributions, and porosity resulting from preheating, specimens measuring approximately 4.8 mm in length and width and 6.6 mm in height were produced using the same Electron Beam Melting (EBM) Additive Manufacturing (AM) system These specimens, containing sintered powder, underwent scanning with a micro-computed tomography (µCT) system (Micro Photonics SkyScan 1172), utilizing multiple continuous scans at an image pixel size of 2 µm and a source voltage of 100 kV The analysis of the µCT data was performed to assess the porosity of the sintered powder, employing ImageJ software for measurement Additionally, particle size distributions were quantified through image analyses conducted with Image-Pro Plus software.

Using CAD software, several simple blocks were designed and subsequently fabricated with the EBM system, utilizing Ti-6Al-4V powder and consistent process parameters as outlined earlier.

Bottom fIgure 7.1 Samples for preheated powder characterization study: (A) powder-bed sample, and (B) powder- enclosed sample.

Tiêu đề	Additive Manufacturing Innovations, Advances, and Applications
Tác giả	Jae-Won Choi, Yanfeng Lu, Ryan B. Wicker, Xibing Going, James Lydon, Kenneth Cooper, Kevin Chou, Pooran C. Joshi, Teja Kuruganti, Chad E. Duty, Jean-Pierre Kruth, Sasan Dadbakhsh, Bey Vrancken, Karolien Kempen, Jef Vleugels, Jan Van Humbeeck, Sara Maria Giannitelli, Pamela Mozetic, Marcella Trombetta, Alberto Rainer, Abinand Rangesh
Người hướng dẫn	tt.S. Sudarshan
Trường học	CRC Press
Thể loại	edited book
Năm xuất bản	2016
Thành phố	Boca Raton

Định dạng
Số trang	448
Dung lượng	21,5 MB