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3d food printing, extrusion, food waste, sustainability, dysphagia, hydrocolloids, Science, Manufactures, and TS1-2301

Food waste utilisation and zero waste approach are among the many ways of building a sustainable economy. Food waste as authentic edible food being accepted by the consumers still has many barriers to overcome. One tool to help in the valorisation of food waste to value-added products is three-dimensional food printing (3DFP). These products can lead to easier and greater acceptance of food waste by consumers, having familiar nature with respect to taste, texture and appearance as other consumables. In the present study, food ink recipes were formulated from spinach stems and kale stalks, the common green leafy vegetable wastes. These spinach and kale inks were then characterised on their rheological properties of shear thinning and yield stress. The inks were subjected to IDDSI tests meant for standardisation of soft foods for dysphagia patients. This paper demonstrates ways of converting vegetable wastes into edible diets that are aesthetically pleasing through 3DFP.

3d printing, additive manufacturing, cooperative robots, mobile robots, teams of robots, cooperative printing, Science, Manufactures, and TS1-2301

Additive manufacturing (AM) is a key enabler and technological pillar of the fourth industrial revolution (Industry 4.0) as it increases productivity and improves resource efficiency. However, current AM systems present some limitations in terms of fabrication time, versatility, and efficiency. The concept of teams of robots represents a novel approach for AM aiming to address these limitations. This review paper discusses the current state-of-the-art of the use of cooperative AM systems based on gantry systems, robotic arms, and mobile robots. The information flow, path planning and slicing strategies are discussed in detail, and several examples of the use of cooperative AM systems are provided. Finally, major research challenges and future perspectives are discussed.

miniaturisation, compliant mechanisms, customization, design automation, design synthesis, Science, Manufactures, and TS1-2301

Micro-additive manufacturing techniques have the potential to meet the demand for miniaturised functional components for minimally invasive surgical instruments. These techniques create monolithic, compliant mechanisms with micro-sized free-form structures that can be tailored to patient-specific surgical procedures. The automated design synthesis of the mechanisms using building blocks results in structures that are shape-programmable. This is achieved through an algorithmic-based computational workflow, which automatically converts user-specified 2D and 3D curves into discrete curve segments. The actuated motion of the mechanisms can be designed to move in a specific way, both forwardly and inversely. The mechanisms are manufactured using micro-laser powder bed fusion and hardenable stainless steel 17-4 PH. By carefully selecting the process parameters, it is possible to 3D-print micro-sized features such as a compliant beam thickness of 80 μm and an actuation hole of 100 μm. Both 2D planar curved mechanisms and 3D spatial curved mechanisms have been implemented and experimentally validated.

laser powder bed fusion, 3d-printing, automation, compliant mechanisms, design synthesis, design freedom, Science, Manufactures, and TS1-2301

Additive manufacturing (AM) facilitates the fabrication of compliant mechanisms through its free-form and design customisation capabilities. Specifically, the properties of kinetic mechanisms such as springs can be extended with regards to their inherent (non-)linear stiffness functions. This allows for the customisation of AM springs according to user preferences. By combining the design synthesis approach of building blocks with the structural optimisation approach for AM, it is possible to define and customise spring stiffness functionalities. The optimisation process employs an automated computational framework based on a genetic algorithm scheme, which has been demonstrated through randomised and reference case studies. This framework enables the attainment of linear, progressive (stiffening), and degressive (softening) stiffness curves. The manufacturability of the springs has been validated through laser powder bed fusion using stainless-steel material 17–4 PH (H900). The springs have resulted in an accuracy error of maximum 6.48% and precision error of maximum 5% through compression testing.

bainitic crossing nose, functionally graded material (fmg), laser directed energy deposition (l-ded), microstructure, wear and rolling contact fatigue (rcf) resistance, Science, Manufactures, and TS1-2301

In this paper, 20Mn2SiCrMo bainitic crossing noses were repaired by depositing 420SS, Stellite 6, 17-4PH and 18Ni300 alloys on the rail surfaces to form functionally graded materials (FGM) using laser directed energy deposition (L-DED) technology. As a result, only 18Ni300 deposit achieves an excellent strength-toughness combination, which possesses a yield strength of ∼1120 MPa together with an impact energy of ∼85.05 J, better than those of substrates (∼1071 MPa, ∼71.34 J). Besides, the wear and rolling contact fatigue (RCF) resistance of 20Mn2SiCrMo/18Ni300 FGM is enhanced to 2.7 and 23.6 times as much as those of substrates. Massive ultrafine nanoprecipitates and a small amount of austenite make 18Ni300 deposit strong enough as well as a certain work-hardenability, ensuring good wear resistance therein; the significant RCF resistance originates from the improved shakedown limit. Therefore, all findings reveal that 18Ni300 is the most promising depositing material for repairing bainitic crossing noses by L-DED.

additive manufacturing, sensor data fusion, thermal imaging, spatter monitoring, shape agnostic monitoring, porosity, Science, Manufactures, and TS1-2301

We developed and applied a novel approach for shape agnostic detection of multiscale flaws in laser powder bed fusion (LPBF) additive manufacturing using heterogenous in-situ sensor data. Flaws in LPBF range from porosity at the micro-scale (< 100 µm), layer related inconsistencies at the meso-scale (100 µm to 1 mm) and geometry-related flaws at the macroscale (> 1 mm). Existing data-driven models are primarily focused on detecting a specific type of LPBF flaw using signals from one type of sensor. Such approaches, which are trained on data from simple cuboid and cylindrical-shaped coupons, have met limited success when used for detecting multiscale flaws in complex LPBF parts. The objective of this work is to develop a heterogenous sensor data fusion approach capable of detecting multiscale flaws across different LPBF part geometries and build conditions. Accordingly, data from an infrared camera, spatter imaging camera, and optical powder bed imaging camera were acquired across separate builds with differing part geometries and orientations (Inconel 718). Spectral graph-based process signatures were extracted from this heterogeneous thermo-optical sensor data and used as inputs to simple machine learning models. The approach detected porosity, layer-level distortion, and geometry-related flaws with statistical fidelity exceeding 93% (F-score).

negative poisson’s ratio, triply periodic minimal surfaces, auxetic structure, bone implant, hip joint, Science, Manufactures, and TS1-2301

Based on the triply periodic minimal surface (TPMS), 3D auxetic structures are successfully implemented using a dual-period function. A series of shape-controllable, dual-period deformation functions are obtained by summarising the characteristics of periodic deformation functions and applying Bezier curve fitting methods. Then, with the geometry originating from the Schwarz primitive (P) of TPMS, the periodic shape transformation of TPMS is achieved using the dual-period deformation functions. The property (negative Poisson’s ratio) of the auxetic structure is investigated based on the control parameters (the TPMS c value, periodic function η, and deformation index γ). The auxetic structures can exhibit excellent 3D negative Poisson’s ratio properties, and the Poisson’s ratio can be effectively adjusted. Moreover, a heterostructure with positive and negative Poisson’s ratio structures is obtained and applied to a stem in the hip joint. The simulation proves that the heterostructure can effectively prevent the failure of the bone implant.

terahertz, metamaterials, 3d printing, mortise and tenon structures, reconfigurable multi-functional, Science, Manufactures, and TS1-2301

The emergence of metamaterial has provided an unprecedented ability to manipulate electromagnetic waves, especially in the terahertz band where there is a lack of natural response materials. However, most metamaterials are fixed single function due to the fixed structure at the beginning of design. The paper reports a reconfigurable multi-functional terahertz metamaterial with variable structures based on mortise and tenon mechanism. And a hybrid 3D printing method based on FDM and E-jet is proposed to fabricate the metamaterials, which simplifies the processing process, improves the speed, and reduces the cost compared to traditional semiconductor processing methods. Through flexible mortise and tenon connections, the metamaterial can achieve: (1) narrowband transmission and broadband absorption; (2) perfect reflection; (3) narrowband reflection and broadband absorption. Relying on ingenious design and processing, the multi-functional metamaterials are expected to be widely used in fields such as electromagnetic shielding, radar stealth, communication and so on.

design workflow, scaffolds, patient-specific, 3d printing, generative design, voronoi, scaffold-guided bone regeneration, Science, Manufactures, and TS1-2301

A streamlined design workflow that facilitates the efficient design and manufacture of patient-specific scaffolds independently applied by the surgical team has been recognised as a key step in a holistic approach towards the envisioned routine clinical translation of scaffold-guided bone regeneration (SGBR). A modular design workflow was developed to semi-automatically fill defect cavities, ensure patient specificity and ideal surgical scaffold insertion for a given surgical approach, add fixation points to secure the scaffolds to the host bone and generate scaffold based on Voronoi, periodic lattice and triply periodic minimal surface pore architectures. The adopted functional representation modelling technique produces models free from 3D printing mesh errors. It was applied to a clinical case of a complicated femoral bone defect. All models were free from mesh errors and the patient-specific fit and unobstructive insertion were validated via digital inspection and physical investigation by way of 3D printed prototypes. The real-time responsiveness of the workflow to user input allows the designer to receive real-time feedback from the surgeon, which is associated with reducing the time to finalise a patient-specific scaffold design. In summary, an efficient workflow was developed that substantially facilitates routine clinical implementation of SGBR through its ability to streamline the design of 3D printed scaffolds.

zirconium alloy, zr-4, additive manufacturing, laser powder bed fusion, annealing, Science, Manufactures, and TS1-2301

Zirconium (Zr) alloys are widely used in nuclear energy because of their excellent mechanical properties and low thermal neutron absorption cross-section. This work investigated the printability, microstructure, and mechanical properties of Zr-4 alloy additively manufactured by laser powder bed fusion (LPBF) for the first time. The effect of annealing temperature on the microstructural and the mechanical property evolution of the printed Zr-4 alloy was studied. The results exhibited that the Zr-4 alloy with a high relative density of 99.77% was obtained using optimised printing parameters. With an increase in the annealing temperature, the formed α phase of the Zr-4 alloy changed from an acicular shape to a coarse-twisted shape, and finally to an equiaxed shape. Such microstructure change endowed the alloy with a high compressive strength of 2130 MPa and compressive strain of 36%. When the annealing temperature exceeded 700°C, Zrx(Fe2Cr) compounds were precipitated, strengthening the alloy by pinning effect. These findings provide valuable guidance for the manufacture of geometrically complex Zr alloy parts for nuclear power applications.