Additive 3D Printing Research Articles

Mechanical properties of additively manufactured octagonal honeycombs

Honeycomb structures have found numerous applications as structural and biomedical materials due to their favourable properties such as low weight, high stiffness, and porosity. Application of additive manufacturing and 3D printing techniques allows for manufacturing of honeycombs with arbitrary shape and wall thickness, opening the way for optimizing the mechanical and physical properties for specific applications. In this study, the mechanical properties of honeycomb structures with a new geometry, called octagonal honeycomb, were investigated using analytical, numerical, and experimental approaches. An additive manufacturing technique, namely fused deposition modelling, was used to fabricate the honeycomb from polylactic acid (PLA). The honeycombs structures were then mechanically tested under compression and the mechanical properties of the structures were determined. In addition, the Euler-Bernoulli and Timoshenko beam theories were used for deriving analytical relationships for elastic modulus, yield stress, Poisson's ratio, and buckling stress of this new design of honeycomb structures. Finite element models were also created to analyse the mechanical behaviour of the honeycombs computationally. The analytical solutions obtained using Timoshenko beam theory were close to computational results in terms of elastic modulus, Poisson's ratio and yield stress, especially for relative densities smaller than 25%. The analytical solutions based on the Timoshenko analytical solution and the computational results were in good agreement with experimental observations. Finally, the elastic properties of the proposed honeycomb structure were compared to those of other honeycomb structures such as square, triangular, hexagonal, mixed, diamond, and Kagome. The octagonal honeycomb showed yield stress and elastic modulus values very close to those of regular hexagonal honeycombs and lower than the other considered honeycombs.

Assessing the use of an infrared spectrum hyperpixel array imager to measure temperature during additive and subtractive manufacturing.

Accurate non-contact temperature measurement is important to optimize manufacturing processes. This applies to both additive (3D printing) and subtractive (material removal by machining) manufacturing. Performing accurate single wavelength thermography suffers numerous challenges. A potential alternative is hyperpixel array hyperspectral imaging. Focusing on metals, this paper discusses issues involved such as unknown or changing emissivity, inaccurate greybody assumptions, motion blur, and size of source effects. The algorithm which converts measured thermal spectra to emissivity and temperature uses a customized multistep non-linear equation solver to determine the best-fit emission curve. Emissivity dependence on wavelength may be assumed uniform or have a relationship typical for metals. The custom software displays residuals for intensity, temperature, and emissivity to gauge the correctness of the greybody assumption. Initial results are shown from a laser powder-bed fusion additive process, as well as a machining process. In addition, the effects of motion blur are analyzed, which occurs in both additive and subtractive manufacturing processes. In a laser powder-bed fusion additive process, the scanning laser causes the melt pool to move rapidly, causing a motion blur-like effect. In machining, measuring temperature of the rapidly moving chip is a desirable goal to develop and validate simulations of the cutting process. A moving slit target is imaged to characterize how the measured temperature values are affected by motion of a measured target.

The Internet of Things in manufacturing innovation processes

Purpose – The purpose of this paper is to contribute and enrich the scientific debate about the phenomenon called the Internet of Things (IoT) from a managerial perspective. Through the lenses of management and innovation literature, the authors investigate the main facts that characterize the IoT and developed a conceptual framework to interpret its evolution. The framework has then been applied to the case of a three-dimensional (3D) printing technology used for additive manufacturing. Design/methodology/approach – A theoretical analysis of the phenomenon of the IoT and its main elements has been performed to construct a conceptual framework in a managerial fashion able to describe the evolutionary impacts of the phenomenon on the manufacturing industry. Findings – Through consequential steps, namely radical, modular, architectural and incremental innovation, and by adopting and integrating the Henderson and Clark model, the authors explain the cornerstones of the evolutionary impact of the IoT on the manufacturing industry. Finally, the authors apply the framework to the case of additive manufacturing and 3D printing. Practical implications – The framework’s practical value is related to its employability in interpreting and possibly forecasting the evolution of manufacturing industries thanks to the advent of the IoT, allowing managers to capture value arising from technological changes. Originality/value – This study offers a clear and simple model to interpret the impacts of the IoT. Such a goal has been obtained by systematizing the disconnected research on the topic and arranging such contributions into solid paradigms of the managerial literature.

The space additive revolution of CRP USA

CRP USA, founded in 2008, is strategically located in the heart of NASCAR country in North Carolina, and specializes in additive manufacturing and 3D printing applications with Windform materials. CRP USA manufactures on-car and wind tunnel components for racing teams. It has taken this expertise to new heights to produce parts for the space (Satellite and CubeSat structures), entertainment and automotive industries using Windform Additive Manufacturing. The Director of Operations of CRP USA is Stewart Davis, who has been working in the field of Additive Manufacturing for two decades. CRP USA has deep expertise in the technology of Selective Laser Sintering with Windform materials, developed in the late 1990s by CRP Technology, the Italian company part of the CRP Group.

Utility and challenges of 3 D Printing

This paper is all about the advanced technology of 3D printing, their implementation in the respective fields and its significant contribution in the global world of science and medical. In this paper we will deal with the term Additive Manufacturing or 3D Printing and a little bit of its history. Its various applications along with the type of materials used in the 3-D are also described. We shall also throw some light on the numerous opportunities provided by this emerging technology as well as the risks and challenges related to it. Its environmental aspects are also shown in the paper. Lastly the scope and scenario in future potential of 3D printing is also evaluated.

Image Processing Assisted Tools for Pre- and Post-processing Operations in Additive Manufacturing

Additive Manufacturing (AM) or 3D printing (3DP) process is a layer by layer manufacturing approach for manufacturing parts with complex geometries. The STL (Stereolithography) file format is the de-facto industry standard for manufacturing parts by AM/3DP. The STL file is a triangular mesh representation of CAD geometry in non-uniform rational B-spline (NURBS) surface format and thus is an approximation of actual part geometry. During the conversion of a complex CAD geometry to an STL file, geometric errors are introduced in the model. These drawbacks associated with the STL file may translate into a faulty or inaccurate final manufactured part. This paper presents a novel Image Processing (IP) based Direct CAD Slicer, IPSlicer, which can be used to manufacture components directly from CAD geometry (without converting to STL file). Using sectional image snapshots of a part, captured normal to the build direction and sectional 2D bounding box data, contour points for each section are identified by performing boundary tracing operation followed by application of Contour Mapping Algorithm (CMA). The method slices the actual NURBS geometry and thus parts manufactured by this method have reduced GD&T errors such as flatness, cylindricity, and profile error. In addition, a support removability analysis tool is developed by performing color-based segmentation on sectional image snapshots in conjunction with a pixel traversal approach. Using the segmented images and sectional bounding box, a sintering area and time calculation tool for each layer is also developed. The effectiveness of IPSlicer is verified by virtually manufacturing test components and calculating GD&T errors by the application of computational metrology algorithms on virtually manufactured data. The support removability analysis tool as well as sintering time and area calculator are validated using several test parts.

A Method to Improve the Fracture Toughness Using 3D Printing by Extrusion Deposition

Additive manufacturing or 3D printing have strongly been developed the last years and currently propose several solutions. Fused Deposition Modeling (FDM) is a layer additive manufacturing process that uses a thermoplastic filament by fused deposition which builds its geometry along trajectories generated by slicing. This process leads to a locally heterogeneous structure because of the weld lines between the deposed threads. These trajectories (and then the weld lines) are predefined and not necessarily based on the specific mechanical constraints from product’s use. As a consequence, the weld lines can be found oriented in bad directions that reduce the mechanical strength of the printed sample. In this work we used finite elements simulation to identify the principal directions of the stress in a standard Crack Test C-T sample. The aim is to reproduce the principal stress directions inside the internal structure of cracking sample realized in extrusion deposition by 3D printing in order to improve the fracture toughness. Several samples made from Acrylonitrile-Butadiene-Styrene were printed and tested. We analyze the outcomes by comparing a C-T standard tensile test procedure with classical and optimized filament depositions. The tests show improved mechanical characteristics and thus provide a method to deposit a filament along a trajectory adapted to the mechanical stresses. Crack branching is observed through a heterogeneous structure and then discussed. On the basis of these results, the cracked specimen will define a new strategy to reinforce the specimen by a specific fused deposit lines.

Mechanical behavior of additively manufactured porous biomaterials made from truncated cuboctahedron unit cells

Fueled by continuous improvements in the additive manufacturing and 3D printing technologies, additively manufactured porous biomaterials have been receiving increasing attention during the last few years particularly for application in orthopedics. The mechanical properties of porous biomaterials are of paramount importance for any such application, as both osseointegration and implant performance are dependent on the spatial distribution of mechanical properties within the implant. In this paper, we studied the mechanical properties of porous biomaterials based on a relatively new type of repeating unit cell, namely truncated cuboctahedron. Analytical relationships were obtained to estimate the elastic modulus, Poisson׳s ratio, and yield stress of the above-mentioned porous biomaterials given the dimensions of their repeating unit cell. The analytically predicted mechanical properties were compared with computational results obtained in the current study and with experimental observations from one of our recent studies on selective laser melted porous titanium (Ti–6Al–4V) biomaterials. Both the Euler–Bernoulli and Timoshenko beam theories were used for the analytical study. The analytically calculated and computationally predicted elastic moduli and Poisson׳s ratios were found to be in good agreement, provided that the analytical solution was based on Timoshenko beam theory. The analytical yield stress based on both the Euler–Bernoulli and Timoshenko beam theories were close to each other and to the numerical results. The elastic moduli predicted using both analytical and computational approaches based on Timoshenko beam theory were in good agreement with experimental observation for smaller values of the relative density, but both approaches somewhat over-predicted the elastic moduli for larger values of the relative density (i.e. >0.3). As for the yield stress, the experimental values were between the two lines corresponding to the yield stresses predicted for the two most critical points of the porous structures, indicting good agreement between experimental, analytical, and computational values of yield stress.

Thermo Mechanical Modeling of Selective Inhibition Sintered Thermoplastic Parts

Contemporary product design and development efforts of various engineering organizations have experienced the emergence of Additive Manufacturing (AM) or 3D printing technology as a competent fabrication option for converting digital data into physical parts without using part-specific tools or fixtures. This paper presents the results of coupled field structural thermal analysis carried out on an innovative variant of AM technology called selective inhibition sintering wherein near net shape parts are fabricated through sintering of thin layers of powdered material while inhibiting the boundaries. Thermal gradients that are inherent to the process cause significant residual stresses affecting the part stability. Hence this study evaluates the effect of layer thickness and heater spot size on temperature gradient, displacement and thermal stress of two different polymers is assessed by numerical analysis. Results of the current study are relevant to enhancing the quality of sintered polymer parts with reference to dimensional fidelity and stability.

Printability of elastomer latex for additive manufacturing or 3D printing

ABSTRACTAdditive manufacturing, sometimes referred to as 3D printing is a new, rapidly developing technology which has the potential to revolutionize fabrication of certain high value, complex products. Until now conventional elastomers have not been widely used in the additive manufacturing process. The goal of our work was to determine the feasibility of additive manufacturing using ink jet printing of elastomeric latex materials. Particle size, viscosity, and surface tension were measured for five different latex materials—poly(2‐chloro‐1,3‐butadiene), carboxylated styrene‐butadiene rubber, carboxylated butadiene‐acrylonitrile copolymer, natural rubber, and prevulcanized natural rubber. The XSBR latex was predicted as the one most likely to be printable. Printing trials carried out with the XSBR as the ink proved it to be printable, although technical problems of agglomeration and print head clogging need to be addressed and both the material and process need to be optimized for consistent printing to be achieved. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 42931.

Additive manufacturing for consumer-centric business models: Implications for supply chains in consumer goods manufacturing

Digital fabrication—including additive manufacturing (AM), rapid prototyping and 3D printing—has the potential to revolutionize the way in which products are produced and delivered to the customer. Therefore, it challenges companies to reinvent their business model—describing the logic of creating and capturing value. In this paper, we explore the implications that AM technologies have for manufacturing systems in the new business models that they enable. In particular, we consider how a consumer goods manufacturer can organize the operations of a more open business model when moving from a manufacturer-centric to a consumer-centric value logic. A major shift includes a move from centralized to decentralized supply chains, where consumer goods manufacturers can implement a “hybrid” approach with a focus on localization and accessibility or develop a fully personalized model where the consumer effectively takes over the productive activities of the manufacturer. We discuss some of the main implications for research and practice of consumer-centric business models and the changing decoupling point in consumer goods' manufacturing supply chains.

Development Trends in Additive Manufacturing and 3D Printing

Development Trends in Additive Manufacturing and 3D Printing

Single Camera Photogrammetry for Reverse Engineering and Fabrication of Ancient and Modern Artifacts

Photogrammetry has been used for recording objects for well over one hundred and fifty years. Modern photogrammetry, or digital image capture, can be used with the aid of a single medium range digital single lens reflex (DSLR) camera, to transform two-dimensional images into three-dimensional CAD spatial representations, and together with the use of additive manufacturing or 3D Printing technology, geometric representations of original cultural, historic and geological artifacts can be fabricated in a process known as Reverse Engineering. Being able to replicate such objects is of great benefit in education; if the original object cannot be handled because it is too old or delicate, then replicas can give the handler a chance to experience the size, texture and weight of rare objects. Photogrammetry equipment is discussed, the objective being simplicity of execution for eventual realisation of physical products such as the artifacts discussed. As the processing power of computers has increased and become more widely available, and with the use of computer software programs it is now possible to digitally combine multi-view photographs, taken from 360° around the object, into 3D CAD representational virtual images. The resulting Data is then reprocessed, with a secondary computer program, to produce the STL file that the additive manufacturing machines can read, so as to produce replicated models of the originals. Three case studies are documented: the reproduction of a small modern clay sculpture; a 3000-year-old Egyptian artifact; and an Ammonite fossil, all successfully recreated, using additive manufacturing technology.

Universities boast AM interests at record Nottingham Conference

In an earlier issue of Metal Powder Report we previewed the important International Conference on Additive Manufacturing & 3D Printing that took place at the Nottingham Belfry Hotel, UK, in July 2014. Consulting Editor Kenneth J A Brookes delivers our comprehensive report on the Conference, which exceeded all expectations.

Additive Manufacturing of Micro‐sized Parts

AbstractAdditive Manufacturing (AM) or 3D printing defines a family of technologies for making objects of almost any shape from virtual 3D model data through additive processes in which successive layers of material are laid down. Laser‐based AM processes like laser‐sintering, selective laser‐melting or stereolithography, differ in the materials that can be used as well as the smallest features that can be achieved in the final parts. Driven by the trend of miniaturization, common high‐resolution AM technologies like stereolithography reach their limitations, when the typical layer thickness in the range of 50 to 150 μm does not suffice to meet application demands. This is where the innovative technique of 3D laser lithography provides a significant advantage. The process of two‐photon polymerization enables the fabrication of high‐resolution 3D micro‐objects with heights from a few hundred nanometers up to several millimeters and layer thicknesses well below 1 μm.

Special Issue: Additive Manufacturing (AM) and 3D Printing

Special Issue: Additive Manufacturing (AM) and 3D Printing

Super-resolution electrohydrodynamic (EHD) 3D printing of micro-structures using phase-change inks

This paper presents a super-resolution 3D printing process using electrohydrodynamic (EHD) printing technology for the direct fabrication of micro-scale structures with phase-change inks (i.e. wax). In this work, we successfully apply EHD printing process for phase-change ink (wax), which is widely used modeling and supporting material for additive manufacturing and 3D printing, to achieve micro-scale droplet dimension. Moreover, a Finite Element Analysis (FEA) model is developed to predict the droplet formation and droplet size of the EHD printing at different printing voltage. The EHD printing process is capable of producing high aspect-of-ratio 3D structures with sub-10μm feature resolution.

Rapid production of cyclonic spray chambers for inductively coupled plasma applications using low cost 3D printer technology

Rapid production of prototype cyclonic spray chambers to enhance research using low-cost additive 3D printing technology.