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Purpose: In flexible electronics applications, organic inks are mostly used for inkjet printing. Three-dimensional (3 D) printing technology has the advantages of low cost, high speed and good precision in modern electronic printing. The purpose of this study is to solve the high cost of traditional printing and the pollution emissions of organic ink. It is necessary to develop a water-based conductive ink that is easily degradable and can be 3 D printed. A nano-silver ink printed circuit pattern with high precision, high conductivity and good mechanical properties is a promising strategy. Design/methodology/approach: The researched nano-silver conductive ink is mainly composed of silver nanoparticles and resin. The effect of adding methyl cellulose on the ink was also explored. A simple 3 D circuit pattern was printed on photographic paper. The line width, line length, line thickness and conductivity of the printed circuit were tested. The influence of sintering temperature and sintering time on pattern resistivity was studied. The relationship between circuit pattern bending performance and electrical conductivity is analyzed. Findings: The experimental results show that the ink has the characteristics of low silver content and good environmental protection effect. The printing feasibility of 3 D printing circuit patterns on paper substrates was confirmed. The best printing temperature is 160°C–180°C, and the best sintering time is 30 min. The circuit pattern can be folded 120°, and the cycle is folded more than 60 times. The minimum resistivity of the circuit pattern is 6.07 µΩ·cm. Methyl cellulose can control the viscosity of the ink. The mechanical properties of the pattern have been improved. The printing method of 3 D printing can significantly reduce the sintering time and temperature of the conductive ink. These findings may provide innovation for the flexible electronics industry and pave the way for alternatives to cost-effective solutions. Originality/value: In this study, direct ink writing technology was used to print circuit patterns on paper substrates. This process is simple and convenient and can control the thickness of the ink layer. The ink material is nonpolluting to the environment. Nano-silver ink has suitable viscosity and pH value. It can meet the requirements of pneumatic 3 D printers. The method has the characteristics of simple process, fast forming, low cost and high environmental friendliness. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this paper is to clarify the relationship between the use of different polymer matrices for the preparation of composite materials, namely, polyethylene terephthalate-glycol (PET-G) and polyamide (PA), using Composite Fiber Co-Extrusion technology with the application of two types of carbon fibers, short and continuous. The aim of the study is also to extend the knowledge of the production of composite materials with a defined structure from the point of view of their influence on the microstructure and their physical-mechanical properties. Design/methodology/approach: As part of the experiment, four types of samples were prepared, namely, two types of samples with PA polymer matrix and two types with PET-G polymer matrix. All types contained short carbon fibers and always one set from each polymer matrix in addition to continuous carbon fibers. All types were prepared using the same 3D printing parameters to avoid any further influence. The samples were then tested for microstructure using microCT, mechanical properties using a tensile test and dilatation characteristics from the point of view of aerospace applications. Finally, the raw materials themselves were tested. Findings: The paper provides insight into the influence of polymer matrix types on the physico-mechanical properties of 3D printed composites. The analysis confirmed that the physico-mechanical results varied with respect to the interface between the polymer matrix and the carbon fiber. The implications of the conclusions can be extended to the development of products in the aerospace and automotive sectors. Originality/value: This study provides information for composite applications in the aerospace industry, focusing on evaluating dilatation characteristics within very low temperatures (−60 °C) when using carbon fibers (continuous carbon fibers, short carbon fibers and a combination of both) in two types of thermoplastic matrices. This perspective on materials characterisation for aerospace applications is a very important and unpublished approach within the 3D printing of composites. These characteristics are important parameters in the design of prototypes and functional samples with regard to the resulting behaviour in real conditions. [ABSTRACT FROM AUTHOR]

Purpose: This paper aims to present an integrated system designed for quality control and inspection in additive manufacturing (AM) technologies. Design/methodology/approach: The study undertakes a comprehensive examination of the process in three distinct stages. First, the quality of the feedstock material is inspected during the preprocessing step. Subsequently, the main research topic of the study is directed toward the 3D printing process itself with real-time monitoring procedures using computer vision methods. Finally, an evaluation of the 3D printed parts is conducted, using measuring methods and mechanical experiments. Findings: The main results of this technical paper are the development and presentation of an integrated solution for quality control and inspection in AM processes. Originality/value: The proposed solution entails the development of a promising tool for the optimization of the quality in 3D prints based on machine learning algorithms. [ABSTRACT FROM AUTHOR]

Purpose: Part building orientation (PBO) is an important factor affecting the quality of laser powder bed fusion (L-PBF), which can affect the surface quality and manufacturing cost. The purpose of this paper is to propose a PBO optimization method to optimize the surface roughness and molding time of parts at the same time on the premise of small calculation scale and arbitrary resolution. Design/methodology/approach: Efficient and accurate evaluation is an important index of PBO optimization method. In this paper, a PBO optimization method based on scaling enumeration method is proposed, and the surface roughness and molding time of L-PBF parts are modeled as the objective evaluation function of PBO optimization process. To realize multi-objective optimization, an expert system is established, and the fuzzy multiple-attribute group decision-making theory is used to provide weights for each objective evaluation function. Findings: Research shows that the scaling-enumeration method can optimize the surface roughness and molding time at the same time and get the best PBO. Compared with the traditional method, the surface roughness and molding time are reduced by 1.1% and 0.58%, respectively, and the operation scale of the scaling-enumeration method is reduced by 99% compared with the traditional method. PBO with arbitrary angular resolution can be achieved. Originality/value: This paper presents a new method to optimize the forming direction of L-PBF parts. This method has small operation scale and accurate results, so it is meaningful for industrial application. [ABSTRACT FROM AUTHOR]

Purpose: This paper aims to propose a method for automatic design of additive manufacturing (AM) flow channel paths driven by path length and pressure loss. The research focuses on the automatic design of channel paths, intending to achieve the shortest flow channel length or minimum pressure loss and improve the design efficiency of AM parts. Design/methodology/approach: The initial layout of the flow channels is redesigned to consider the channels print supports. Boundary conditions and constraints are defined according to the redesigned channels layout, and the equation consisting of channel length and pressure loss is used as the objective function. Then the path planning simulation is performed based on particle swarm algorithm. The proposed method describes the path of flow channels using spline cures. The spline curve is controlled by particle (one particle represents a path), and the particle is randomly generated within the design space. After the path planning simulation is completed, the generated paths are used to create 3D parts. Findings: Case study 1 demonstrates the automatic design of hydraulic spool valve. Compared to conventional spool valve, the pressure loss was reduced by 86% and the mass was reduced by 83%. The design results of case study 2 indicate that this approach is able to find the shortest channel path with lower computational cost. Originality/value: The automatic design method of flow channel paths driven by path length and pressure loss presented in this paper provides a novel solution for the creation of AM flow components. [ABSTRACT FROM AUTHOR]

Purpose: The lightweight design of aircraft seats can significantly improve fuel efficiency and reduce greenhouse gas emissions. Metal additive manufacturing (MAM) can produce lightweight topology-optimized designs with improved performance, but limited build volume restricts the printing of large components. The purpose of this paper is to design a lightweight aircraft seat leg structure using topology optimization (TO) and MAM with build volume restrictions, while satisfying structural airworthiness certification requirements. Design/methodology/approach: TO was used to determine a lightweight conceptual design for the seat leg structure. The conceptual design was decomposed to meet the machine build volume, a detailed CAD assembly was designed and print orientation was selected for each component. Static and dynamic verification was performed, the design was updated to meet the structural requirements and a prototype was manufactured. Findings: The final topology-optimized seat leg structure was decomposed into three parts, yielding a 57% reduction in the number of parts compared to a reference design. In addition, the design achieved an 8.5% mass reduction while satisfying structural requirements for airworthiness certification. Originality/value: To the best of the authors' knowledge, this study is the first paper to design an aircraft seat leg structure manufactured with MAM using a rigorous TO approach. The resultant design reduces mass and part count compared to a reference design and is verified with respect to real-world aircraft certification requirements. [ABSTRACT FROM AUTHOR]

Purpose: This study aims to identify research trends and technological evolution in the polymer three-dimensional (3D) printing process that can effectively identify the direction of technological advancement and progress of acceptance in both society and key manufacturing industries. Design/methodology/approach: The Scopus database was used to collect data on polymer 3D printing papers. This study uses bibliometric approach along with network analytic techniques to identify and discuss the most important countries and their scientific collaboration, compares income groups and analyses keyword trends. Findings: It was found that top research production results from heavy investments in research and development. The USA has the highest number of papers among the high-income countries. However, scientific production in the other two income groups is strongly dominated by China and India. Keyword analysis shows that countries with lower incomes in certain areas, such as composite and bioprinting, have fallen behind other groups over time. International collaborations were suggested as mechanisms for those countries to catch up with the current research trends. The evolution of the research field, which started with a focus on 3D printing processes and shifted to printed part designs and their applications, was discussed. The advancement of the research topic suggests that translational research on polymer 3D printing has been led mainly by research production from higher-income countries and countries with large research and development investments. Originality/value: Previous studies have conducted performance analysis, science mapping and network analysis in the field of 3D printing, but none have focused on global research trends classified by country income. This study has conducted a bibliometric analysis and compared the outputs according to various income levels according to the World Bank classification. [ABSTRACT FROM AUTHOR]

Purpose This paper aims to investigate the applicability of 3D-printed molds to be used as a substitute for photolithography in the formation of polymer-based stamps. It proposes leveraging 3D printing as a rapid prototyping tool to be applied to microfluidic fabrication.Design/methodology/approach Different designs are created using computer-aided design (CAD) software and printed via Makerbot 3D printer. The molds serve as negative reliefs for a PDMS stamp. The stamp is used to apply paraffin wax to chromatography paper, creating hydrophobic barriers and hydrophilic channels. The minimum functional channel widths and barrier widths are determined for the method.Findings The method is demonstrated to be effective for bypassing the more cost-prohibitive photolithography approach for rapid paper microdevice fabrication. This approach produces functional channels that can be used for on-chip analytical assays. The minimum functional barrier widths and minimum functional channel widths are in good agreement with other published methods for paper-based microchannel fabrication.Research limitations/implications The approach cannot generate the high-resolution structures possible with photolithography. Therefore, if higher resolutions are needed for a particular application, this approach is not the best.Practical implications The simplicity of the approach introduces an affordable method to create disposable devices that can be used at the point of testing.Originality/value The paper satisfies a need for inexpensive, rapid prototyping of paper-based devices. The method is simple and can be used as a tool for introducing labs to microfluidics research. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this paper is to study a feasible visualization of large-size three-dimension (3D) color models which are beyond the maximum print size of newest paper-based 3D printer used 3D cutting-bonding frame (3D-CBF) and evaluate the effects of cutting angle and layout method on printing time of designed models. Design/methodology/approach: Sixteen models, including cuboid model, cylinder model, hole model and sphere model with different shape features, were divided into two symmetric parts and printed by the Mcor IRIS HD 3D printer. Before printing, two sub-parts were rearranged in one of three layout methods. Nine scaled sizes of original models were printed to find the quantitative relationship between printing time and scale values in each type. For the 0.3 times of original models, six cutting angles were evaluated in detail. Findings: The correlation function about colorization time and printed pages was proposed. Based on 3D-CBF, the correlation between printing time and scale size is statistically defined. Optimization parameters of designed parts visualization about cutting angel and layout method were found, even if their statistical results were difficult to model their effects on printing time of specimens. Research limitations/implications: The research is comparative and limited to the special models and used procedures. Originality/value: The paper provides a feasible visualization and printing speed optimization methods for the further industrialization of 3D paper-based printing technology in cultural creative field. [ABSTRACT FROM AUTHOR]

Purpose: Additive manufacturing also known as 3D printing is an evolving advanced manufacturing technology critical for the new era of complex machinery and operating systems. Manufacturing systems are increasingly faced with risk of attacks not only by traditional malicious actors such as hackers and cyber-criminals but also by some competitors and organizations engaged in corporate espionage. This paper aims to elaborate a plausible risk practice of designing and demonstrate a case study for the compromised-based malicious for polymer 3D printing system. Design/methodology/approach: This study assumes conditions when a machine was compromised and evaluates the effect of post compromised attack by studying its effects on tensile dog bone specimens as the printed object. The designed algorithm removed predetermined specific number of layers from the tensile samples. The samples were visually identical in terms of external physical dimensions even after removal of the layers. Samples were examined nondestructively for density. Additionally, destructive uniaxial tensile tests were carried out on the modified samples and compared to the unmodified sample as a control for various mechanical properties. It is worth noting that the current approach was adapted for illustrating the impact of cyber altercations on properties of additively produced parts in a quantitative manner. It concurrently pointed towards the vulnerabilities of advanced manufacturing systems and a need for designing robust mitigation/defense mechanism against the cyber altercations. Findings: Density, Young's modulus and maximum strength steadily decreased with an increase in the number of missing layers, whereas a no clear trend was observed in the case of % elongation. Post tensile test observations of the sample cross-sections confirmed the successful removal of the layers from the samples by the designed method. As a result, the current work presented a cyber-attack model and its quantitative implications on the mechanical properties of 3D printed objects. Originality/value: To the best of the authors' knowledge, this is the original work from the team. It is currently not under consideration for publication in any other avenue. The paper provides quantitative approach of realizing impact of cyber intrusions on deteriorated performance of additively manufactured products. It also enlists important intrusion mechanisms relevant to additive manufacturing. [ABSTRACT FROM AUTHOR]

Purpose: This paper aims to investigate the current state of biocomposites used in fused deposition modelling (FDM) with a focus on their mechanical characteristics. Design/methodology/approach: The study presents a variety of biocomposite materials that have been used in filaments for 3D printing by different researchers. The process of making filaments is then described, followed by a discussion of the process parameters associated with the FDM. Findings: To achieve better mechanical properties of 3D-printed parts, it is essential to optimize the process parameters of FDM while considering the characteristics of the biocomposite material. Polylactic acid is considered the most promising matrix material due to its biodegradability and lower cost. Moreover, the use of natural fibres like hemp, flax and sugarcane bagasse as reinforcement to the polymer in FDM filaments improves the mechanical performance of printed parts. Originality/value: The paper discusses the influence of critical process parameters of FDM like raster angle, layer thickness, infill density, infill pattern and extruder temperature on the mechanical properties of 3D-printed biocomposite. [ABSTRACT FROM AUTHOR]

Purpose: This paper aims to investigate the influence of scan speed on the corrosion and tribocorrosion features of the CoCrMoW samples fabricated via the selective laser melting (SLM) process. Design/methodology/approach: CoCrMoW samples were produced by SLM at different scan speeds. Produced samples were made via structural surveys (X-ray diffraction examinations and scanning electron microscopic analyses), hardness measurements and electrochemical and tribocorrosion experiments. Findings: Outcomes displayed that the corrosion and tribocorrosion properties of CoCrMoW alloy were significantly influenced by scanning speeds. Also, these properties of the alloy increased with increasing scanning speeds. CoCrMoW samples produced at a laser scan speed of 1,000 mm/s showed the best resistance to corrosion and tribocorrosion. This could be related to the high hardness and low grain structure of the fabricated samples. Originality/value: This paper may be a practical reference and offers insight into the effect of scanning speeds on the increase of hardness, tribological and corrosion performance of CoCrMoW alloys. This study can help in the further advancement of cobalt-chromium alloy in situ produced by SLM for both electrochemical and tribocorrosion behavior for biomedical applications. [ABSTRACT FROM AUTHOR]

Purpose: Stab-resistant body armor (SRBA) is used to protect the body from sharp knives. However, most SRBA materials currently have the disadvantages of large weight and thickness. This paper aims to prepare lightweight and high-performance SRBA by 3D printing truss structure and resin-filling method. Design/methodology/approach: The stab resistance truss structure was prepared by the fused deposition modeling method, and the composite structure was formed after filling with resin for dynamic and quasi-static stab tests. The optimized structural plate can meet the standard GA68-2019. Digital image correlation technology was used to analyze the local strain changes during puncture. The puncture failure mode was summarized by the final failure morphologies. The explicit dynamics module in ANSYS Workbench was used to analyze the design of the overlapped structure stab resistance process in this paper. Findings: The stab resistance performance of the 3D-printed structural plate is affected by the internal filling pattern. The stab resistance performance of 3D-printed structural parts was significantly improved after resin filling. The 50%-diamond-PLA-epoxy, with a thickness of only 5 mm was able to meet the stab resistance standard. Resins are used to increase the strength and hardness of the material but also to increase crack propagation and reduce the toughness of the material. The overlapping semicircular structure was inspired by the exoskeleton structure of the demon iron beetle, which improved the stab resistance between gaps. The truss structure can effectively disperse stress for toughening. The filled resin was reinforced by absorbing impact energy. Originality/value: The 3D-printed resin-filled truss structure can be used to prepare high-performance stab resistance structural plates, which balance the toughness and strength of the overall structure and ultimately reduce the thickness and weight of the SRBA. [ABSTRACT FROM AUTHOR]

Purpose: This paper aims to identify the optimal forming angle for the selective laser melting (SLM) process and evaluate the mechanical properties of the SLM-formed GH3536 alloy in the aero-engine field. Design/methodology/approach: Forming the samples with optimized parameters and analyzing the microstructure and properties of the block samples in different forming angles with scanning electron microscope, XRD, etc. so as to analyze and reveal the laws and mechanism of the block samples in different forming angles by SLM. Findings: There are few cracks on the construction surface of SLM formed samples, and the microstructure shows columnar subgrains and cellular subgrains. The segregation of metal elements was not observed in the microstructure. The pattern shows strong texture strength on the (111) crystal plane. In the sample, the tensile strength of 60° sample is the highest, the plasticity of 90° forming sample is the best, the comprehensive property of 45° sample is the best and the fracture mode is plastic fracture. The comprehensive performance of the part is the best under the forming angle of 45°. To ensure the part size, performance and support structure processing, additional dimensions are added to the part structure. Originality/value: In this paper, how to make samples with different forming angles is described. Combined with the standard of forged GH3536 alloy, the microstructure and properties of the samples are analyzed, and the optimal forming angle is obtained. [ABSTRACT FROM AUTHOR]

Purpose: The main objective of this paper is to illustrate an analytical view of different methods of 3D bioprinting, variations, formulations and characteristics of biomaterials. This review also aims to discover all the areas of applications and scopes of further improvement of 3D bioprinters in this era of the Fourth Industrial Revolution. Design/methodology/approach: This paper reviewed a number of papers that carried evaluations of different 3D bioprinting methods with different biomaterials, using different pumps to print 3D scaffolds, living cells, tissue and organs. All the papers and articles are collected from different journals and conference papers from 2014 to 2022. Findings: This paper briefly explains how the concept of a 3D bioprinter was developed from a 3D printer and how it affects the biomedical field and helps to recover the lack of organ donors. It also gives a clear explanation of three basic processes and different strategies of these processes and the criteria of biomaterial selection. This paper gives insights into how 3D bioprinters can be assisted with machine learning to increase their scope of application. Research limitations/implications: The chosen research approach may limit the generalizability of the research findings. As a result, researchers are encouraged to test the proposed hypotheses further. Practical implications: This paper includes implications for developing 3D bioprinters, developing biomaterials and increasing the printability of 3D bioprinters. Originality/value: This paper addresses an identified need by investigating how to enable 3D bioprinting performance. [ABSTRACT FROM AUTHOR]

Purpose: This paper aims to investigate the application of 3D printing technology, particularly using sand-type materials, in the creation of artificial rock models for rock mechanics experimentation. Design/methodology/approach: Using a comprehensive analysis, this research explores the utilization of 3D printing technology in rock mechanics. Sand-type materials are specifically investigated for their ability to replicate natural rock characteristics. The methodology involves a review of recent achievements and experimentation in this field. Findings: The study reveals that sand-type 3D printing materials demonstrate comparable properties to natural rocks, including brittle characteristics, surface roughness, microstructural features and crack propagation patterns. Research limitations/implications: While the research establishes the viability of sand-type 3D printing materials, it acknowledges limitations such as the need for further exploration and validation. Generalizability may be constrained, warranting additional research to address these limitations. Originality/value: This research contributes insights into the potential application of sand-type 3D printing materials in indoor rock physics experiments. The findings may guide future endeavors in fabricating rock specimens with consistent structures for practical rock mechanics applications. [ABSTRACT FROM AUTHOR]

Purpose: Selective jet electrodeposition (SJED) is an emerging additive manufacturing (AM) technology for realizing metallic components of nano and micro sizes. The deposited parts on the substrate form metallurgical bonding, so separating them from the substrate is an unsolved issue. Therefore, this paper aims to propose a method for separating the deposited micro parts from a sacrificial substrate. Furthermore, single and multi-bead optimization is performed to fabricate microparts with varying density. Design/methodology/approach: A typical SJED process consists of a nozzle (to establish a column of electrolytes) retrofitted on a machine tool (to provide relative motion between substrate and nozzle) that deposits material atom-by-atom on a conductive substrate. Findings: A comprehensive study of process parameters affecting the layer height, layer width and morphology of the deposited micro-parts has been provided. The uniformity in the deposited parts can be achieved with the help of low applied voltage and high scanning speed. Multi-bead analysis for the flat surface condition is experimentally performed, and the flat surface condition is achieved when the centre distance between two adjacent beads is kept at half of the width of a single bead. Originality/value: Although several literatures have demonstrated that the SJED process can be used for the fabrication of parts; however, part fabrication through multi-bead optimization is limited. Moreover, the removal of the fabricated part from the substrate is the novelty of the current work. [ABSTRACT FROM AUTHOR]

Purpose: Stereolithography (SLA) additive manufacturing (AM) technique has enabled the production of inconspicuous and aesthetically pleasing orthodontics that are also hygienic. However, the staircase effect poses a challenge to the application of invisible orthodontics in the dental industry. The purpose of this study is to implement chemical postprocessing technique by using isopropyl alcohol as a solvent to overcome this challenge. Design/methodology/approach: Fifteen experiments were conducted using a D-optimal design to investigate the effect of different concentrations and postprocessing times on the surface roughness, material removal rate (MRR), hardness and cost of SLA dental parts required for creating a clear customized aligner, and a container was constructed for chemical treatment of these parts made from photocurable resin. Findings: The study revealed that the chemical postprocessing technique can significantly improve the surface roughness of dental SLA parts, but improper selection of concentration and time can lead to poor surface roughness. The optimal surface roughness was achieved with a concentration of 90 and a time of 37.5. Moreover, the dental part with the lowest concentration and time (60% and 15 min, respectively) had the lowest MRR and the highest hardness. The part with the highest concentration and time required the greatest budget allocation. Finally, the results of the multiobjective optimization analysis aligned with the experimental data. Originality/value: This paper sheds light on a previously underestimated aspect, which is the pivotal role of chemical postprocessing in mitigating the adverse impact of stair case effect. This nuanced perspective contributes to the broader discourse on AM methodologies, establishing a novel pathway for advancing the capabilities of SLA in dental application. [ABSTRACT FROM AUTHOR]

Purpose: This study aims to examine how the thickness of layers and printing speed impact the energy absorption capacity of honeycomb structures through drop-weight experiments. In addition, the effect of printing orientation on the resulting microstructure and mechanical performance was targeted to be examined. Design/methodology/approach: In this paper, after manufacturing test specimens using fused deposition modeling technique with three distinct layer thicknesses (0.16 mm, 0.20 mm and 0.28 mm) and printing speeds (40 mm/min, 50 mm/min and 70 mm/min), drop weight tests were carried out. Then to see the effect of printing orientation on mechanical performance, three-point-bending tests were performed and damage mechanisms were comparatively examined through scanning electron microscopy. Findings: An increase in layer thickness from 0.16 mm to 0.28 mm resulted in a notable 37% decrease in the impact resistance of the printed part. In addition, increasing the printing speed from 50 to 70 mm/min reduced the energy absorption capacity of the printed part by approximately 36.5%. Moreover, in terms of printing direction, transversely printed specimens showed 10% lower flexural strength than longitudinally printed specimens. Finally, scanning electron microscopy (SEM) observation showed that internal defects were more prominent in transversely printed specimens, resulting in premature failure. Furthermore, delamination was also detected in transversely printed specimens as another damage mechanism accelerating material failure. Originality/value: It is seen that the effect of printing parameters on the fundamental mechanical properties including tensile strength, strain at break, ductility and elastic modulus were studied by various researchers. However, to the best of authors' knowledge, the effect of printing speed and layer thickness on the energy absorption of polylactic acid based hexagonal honeycomb was not encountered. In addition, in-depth SEM analysis to discover the influence of printing direction significantly contributes to the literature. [ABSTRACT FROM AUTHOR]

Purpose: Three-dimensional (3D) printing is popular for many applications including the production of photocatalysts. This paper aims to focus on developing of 3D-printed photocatalyst-nano composite lattice structure. Digital light processing (DLP) 3D printing of photocatalyst composites was performed using photosensitive resin mixed with 0.5% Wt. of TiO2 powder and varying amounts (0.025% Wt. to 0.2% Wt.) of graphene nanoplatelet powder. The photocatalytic efficiency of DLP 3D-printed photocatalyst TiO2 composite was investigated, and the effects of nano graphite powder incorporation on the photocatalytic activity, thermal and mechanical properties were investigated. Design/methodology/approach: Methods involve 3D computer-aided design modeling, printing parameters and comprehensive characterization techniques such as structural equation modeling, X-ray diffraction, thermogravimetric analysis, Fourier-transform infrared (FTIR) and mechanical testing. Findings: Results highlight successful dispersion and characteristics of TiO2 and graphene nanoplatelet (GNP) powders, intricate designs of 3D-printed lattice structures, and the influence of GNPs on thermal behavior and mechanical properties. Originality/value: The study suggests applicability in wastewater treatment and environmental remediation, showcasing the adaptability of 3 D printing in designing effective photocatalysts. Future research should focus on practical applications and the long-term durability of these 3D-printed composites. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this paper is to present an optimisation of four-point star-shaped structures produced through additive manufacturing (AM) polylactic acid (PLA). The study also aims to investigate the compression failure mechanism of the structure. Design/methodology/approach: A Taguchi L9 orthogonal array design of the experiment is adopted in which the input parameters are resolution (0.06, 0.15 and 0.30 mm), print speed (60, 70 and 80 mm/s) and bed temperature (55°C, 60°C, 65°C). The response parameters considered were printing time, material usage, compression yield strength, compression modulus and dimensional stability. Empirical observations during compression tests were used to evaluate the load–response mechanism of the structures. Findings: The printing resolution is the most significant input parameter. Material length is not influenced by the printing speed and bed temperature. The compression stress–strain curve exhibits elastic, plateau and densification regions. All the samples exhibit negative Poisson's ratio values within the elastic and plateau regions. At the beginning of densification, the Poisson's ratios change to positive values. The metamaterial printed at a resolution of 0.3 mm, 80 mm/s and 60°C exhibits the best mechanical properties (yield strength and modulus of 2.02 and 58.87 MPa, respectively). The failure of the structure occurs through bending and torsion of the unit cells. Practical implications: The optimisation study is significant for decision-making during the 3D printing and the empirical failure model shall complement the existing techniques for the mechanical analysis of the metamaterials. Originality/value: To the best of the authors' knowledge, for the first time, a new empirical model, based on the uniaxial load response and "static truss concept", for failure mechanisms of the unit cell is presented. [ABSTRACT FROM AUTHOR]

Purpose: Fused Filament Fabrication (FFF) is one of the growing technologies in additive manufacturing, that can be used in a number of applications. In this method, process parameters can be customized and their simultaneous variation has conflicting impacts on various properties of printed parts such as dimensional accuracy (DA) and surface finish. These properties could be improved by optimizing the values of these parameters. Design/methodology/approach: In this paper, four process parameters, namely, print speed, build orientation, raster width, and layer height which are referred to as "input variables" were investigated. The conflicting influence of their simultaneous variations on the DA of printed parts was investigated and predicated. To achieve this goal, a hybrid Genetic Algorithm – Artificial Neural Network (GA-ANN) model, was developed in C#.net, and three geometries, namely, U-shape, cube and cylinder were selected. To investigate the DA of printed parts, samples were printed with a central through hole. Design of Experiments (DoE), specifically the Rotational Central Composite Design method was adopted to establish the number of parts to be printed (30 for each selected geometry) and also the value of each input process parameter. The dimensions of printed parts were accurately measured by a shadowgraph and were used as an input data set for the training phase of the developed ANN to predict the behavior of process parameters. Then the predicted values were used as input to the Desirability Function tool which resulted in a mathematical model that optimizes the input process variables for selected geometries. The mean square error of 0.0528 was achieved, which is indicative of the accuracy of the developed model. Findings: The results showed that print speed is the most dominant input variable compared to others, and by increasing its value, considerable variations resulted in DA. The inaccuracy increased, especially with parts of circular cross section. In addition, if there is no need to print parts in vertical position, the build orientation should be set at 0° to achieve the highest DA. Finally, optimized values of raster width and layer height improved the DA especially when the print speed was set at a high value. Originality/value: By using ANN, it is possible to investigate the impact of simultaneous variations of FFF machines' input process parameters on the DA of printed parts. By their optimization, parts of highly accurate dimensions could be printed. These findings will be of significant value to those industries that need to produce parts of high DA on FFF machines. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this paper is to improve the productivity and quality of the wire arc additive manufacturing process by benchmarking the strategies from the selected six strategies, namely, heat treatment process, inter pass cooling process, inter pass cold rolling process, peening process, friction stir processing and oscillation process. Design/methodology/approach: To overcome the lack of certainty associated with correlations and relationships in quality functional deployment, fuzzy numbers have been integrated with the quality functional deployment framework. Twenty performance measures have been identified from the literature under five groups, namely, mechanical properties, physical properties, geometrical properties, cost and material properties. Using house of quality weights are allocated to performance measures and groups, relationships are established between performance measures and strategies, and correlations are assigned between strategies. Finally, for each strategy, relative importance, score and crisp values are calculated. Findings: Inter pass cold rolling process strategy is computed with the highest crisp value of 15.80 which is followed by peening process, heat treatment process, friction stir processing, inter pass cooling process,] and oscillation process strategy. Originality/value: To the best of the authors' knowledge, there has been no research in the literature that analyzes the strategies to improve the quality and productivity of the wire arc additive manufacturing process. [ABSTRACT FROM AUTHOR]

Purpose: The use of continuous fiber-reinforced filaments improves the mechanical properties obtained with the fused filament fabrication (FFF) process. Yet, there is a lack of simulation tailored tools to assist in the design for additive manufacturing of continuous fiber composites. To build such models, a precise elastic model is required. As the porosity caused by interbead voids remains an important flaw of the process, this paper aims to build an elastic model integrating this aspect. Design/methodology/approach: To study the amount of porosity, which could be a failure initiator, this study proposes a two step periodic homogenization method. The first step concerns the microscopic scale with a unit cell made of fiber and matrix. The second step is at the mesoscopic scale and combines the elastic material of the first step with the interbead voids. The void content has been set as a parameter of the model. The material models predicted with the periodic homogenization were compared with experimental results. Findings: The comparison between periodic homogenization results and tensile test results shows a fair agreement between the experimental results and that of the numerical simulation, whatever the fibers' orientations are. Moreover, a void content reduction has been observed by increasing the crossing angle from one layer to another. An empiric law giving the porosity according to this crossing angle was created. The model and the law can be further used for design evaluation and optimization of continuous fiber-reinforced FFF. Originality/value: A new elastic model considering interbead voids and its variation with the crossing angle of the fibers has been built. It can be used in simulation tools to design high performance fused filament fabricated composite parts. [ABSTRACT FROM AUTHOR]

Purpose: Wire-arc-based additive manufacturing (WAAM) is a promising technology for the efficient and economical fabrication of medium-large components. However, the anisotropic behavior of the multilayered WAAM-fabricated components remains a challenging problem. Design/methodology/approach: The purpose of this paper is to conduct a comprehensive study of the grain morphology, crystallographic orientation and texture in three regions of the WAAM printed component. Furthermore, the interdependence of the grain morphology in different regions of the fabricated component with their mechanical and tribological properties was established. Findings: The electron back-scattered diffraction analysis of the top and bottom regions revealed fine recrystallized grains, whereas the middle regions acquired columnar grains with an average size of approximately 8.980 µm. The analysis revealed a higher misorientation angle and an intense crystallographic texture in the upper and lower regions. The investigations found a higher microhardness value of 168.93 ± 1.71 HV with superior wear resistance in the bottom region. The quantitative evaluation of the residual stress detected higher compressive stress in the upper regions. Evidence for comparable ultimate tensile strength and greater elongation (%) compared to its wrought counterpart has been observed. Originality/value: The study found a good correlation between the grain morphology in different regions of the WAAM-fabricated component and their mechanical and wear properties. The Hall–Petch relationship also established good agreement between the grain morphology and tensile test results. Improved ductility compared to its wrought counterpart was observed. The anisotropy exists with improved mechanical properties along the longitudinal direction. Moreover, cylindrical components have superior tribological properties compared with cuboidal components. [ABSTRACT FROM AUTHOR]

Purpose: Biodegradable polymers are widely used in personalized medical devices or scaffolds for tissue engineering. The manufacturing process should be finished with sterilization procedure. However, it is not clear how the different sterilization methods have an impact on the mechanical strength of the three-dimensional (3D)-printed parts, such as bone models or personalized mechanical devices. This paper aims to present the results of mechanical testing of polylactide-based bone models before and after sterilization. Design/methodology/approach: Polylactide specimens prepared in fused filament fabrication technology were sterilized with different sterilization methods: ultraviolet (UV) and ethylene oxide. Mechanical properties were determined by testing tensile strength, Young's modulus and toughness. Findings: The tensile strength of material after sterilization was significantly higher after ethylene oxide sterilization compared to the UV sterilization, but in both sterilization methods, the specimens characterized lower tensile strength and Young's modulus when compared to the control. In comparison of toughness results, there was no statistically significant differences. The findings are particularly significant in the perspective of using individual implants, bone grafts and dental guides. Originality/value: Although fused filament fabrication (FFF) 3D printing devices equipped with UV light sterilization options are available, experimental results of the effect of selected sterilization methods on the mechanical strength of additively manufactured parts have not been described. This paper completes the present state of the art on the problem of sterilization of FFF parts from biodegradable materials. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this paper is to demonstrate the impact of the welding sequence on the substrate plate distortion during the wire and arc additive manufacturing (WAAM) process. This paper also aims to show the capability of finite element simulations in the prediction of those thermally induced distortions. Design/methodology/approach: An experiment was conducted in which solid aluminum blocks were manufactured using two different welding sequences. The distortion of the substrates was measured at predefined positions and converted into bending and torsion values. Subsequently, a weakly coupled thermo-mechanical finite element model was created using the Abaqus simulation software. The model was calibrated and validated with data gathered from the experiments. Findings: The results of this paper showed that the welding sequence of a part significantly affects the formation of thermally induced distortions of the final part. The calibrated simulation model was able to capture the different distortion behavior attributed to the welding sequences. Originality/value: Within this work, a simulation model was developed capable of predicting the distortion of WAAM parts in advance. The findings of this paper can be used to improve the design of WAAM welding sequences while avoiding high experimental efforts. [ABSTRACT FROM AUTHOR]

Purpose: In pursuit of affordable and nutrient-rich food alternatives, the symbiotic culture of bacteria and yeast (SCOBY) emerged as a selected food ink for 3D printing. The purpose of this paper is to harness SCOBY's potential to create cost-effective and nourishing food options using the innovative technique of 3D printing. Design/methodology/approach: This work presents a comparative analysis of the printability of SCOBY with blends of wheat flour, with a focus on the optimization of process variables such as printing composition, nozzle height, nozzle diameter, printing speed, extrusion motor speed and extrusion rate. Extensive research was carried out to explore the diverse physical, mechanical and rheological properties of food ink. Findings: Among the ratios tested, SCOBY, with SCOBY:wheat flour ratio at 1:0.33 exhibited the highest precision and layer definition when 3D printed at 50 and 60 mm/s printing speeds, 180 rpm motor speed and 0.8 mm nozzle with a 0.005 cm3/s extrusion rate, with minimum alteration in colour. Originality/value: Food layered manufacturing (FLM) is a novel concept that uses a specialized printer to fabricate edible objects by layering edible materials, such as chocolate, confectionaries and pureed fruits and vegetables. FLM is a disruptive technology that enables the creation of personalized and texture-tailored foods, incorporating desired nutritional values and food quality, using a variety of ingredients and additions. This research highlights the potential of SCOBY as a viable material for 3D food printing applications. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this paper is to compare the influence of relative density (RD) and strain rates on failure mechanism and specific energy absorption (SEA) of polyamide lattices ranging from bending to stretch-dominated structures using selective laser sintering (SLS). Design/methodology/approach: Three bending and two stretch-dominated unit cells were selected based on the Maxwell stability criterion. Lattices were designed with three RD and fabricated by SLS technique using PA12 material. Quasi-static compression tests with three strain rates were carried out using Taguchi's L9 experiments. The lattice compressive behaviour was verified with the Gibson–Ashby analytical model. Findings: It has been observed that RD and strain rates played a vital role in lattice compressive properties by controlling failure mechanisms, resulting in distinct post-yielding responses as fluctuating and stable hardening in the plateau region. Analysis of variance (ANOVA) displayed the significant impact of RD and emphasised dissimilar influences of strain rate that vary to cell topology. Bending-dominated lattices showed better compressive properties than stretch-dominated lattices. The interesting observation is that stretch-dominated lattices with over-stiff topology exhibited less compressive properties contrary to the Maxwell stability criterion, whereas strain rate has less influence on the SEA of face-centered and body-centered cubic unit cells with vertical and horizontal struts (FBCCXYZ). Practical implications: This comparative study is expected to provide new prospects for designing end-user parts that undergo various impact conditions like automotive bumpers and evolving techniques like hybrid and functionally graded lattices. Originality/value: To the best of the authors' knowledge, this is the first work that relates the strain rate with compressive properties and also highlights the lattice behaviour transformation from ductile to brittle while the increase of RD and strain rate analytically using the Gibson–Ashby analytical model. [ABSTRACT FROM AUTHOR]

Purpose: This paper aims to present the fabrication of 6061 aluminum alloy (AA6061) using a promising laser additive manufacturing process, called the laser-foil-printing (LFP) process. The process window of AA6061 in LFP was established to optimize process parameters for the fabrication of high strength, dense and crack-free parts even though AA6061 is challenging for laser additive manufacturing processes due to hot-cracking issues. Design/methodology/approach: The multilayers AA6061 parts were fabricated by LFP to characterize for cracks and porosity. Mechanical properties of the LFP-fabricated AA6061 parts were tested using Vicker's microhardness and tensile testes. The electron backscattered diffraction (EBSD) technique was used to reveal the grain structure and preferred orientation of AA6061 parts. Findings: The crack-free AA6061 parts with a high relative density of 99.8% were successfully fabricated using the optimal process parameters in LFP. The LFP-fabricated parts exhibited exceptional tensile strength and comparable ductility compared to AA6061 samples fabricated by conventional laser powder bed fusion (LPBF) processes. The EBSD result shows the formation of cracks was correlated with the cooling rate of the melt pool as cracks tended to develop within finer grain structures, which were formed in a shorter solidification time and higher cooling rate. Originality/value: This study presents the pioneering achievement of fabricating crack-free AA6061 parts using LFP without the necessity of preheating the substrate or mixing nanoparticles into the melt pool during the laser melting. The study includes a comprehensive examination of both the mechanical properties and grain structures, with comparisons made to parts produced through the traditional LPBF method. [ABSTRACT FROM AUTHOR]

Purpose: Because of the advantages of high deposition efficiency and low manufacturing cost compared with other additive technologies, robotic wire arc additive manufacturing (WAAM) technology has been widely applied for fabricating medium- to large-scale metallic components. The additive manufacturing (AM) method is a relatively complex process, which involves the workpiece modeling, conversion of the model file, slicing, path planning and so on. Then the structure is formed by the accumulated weld bead. However, the poor forming accuracy of WAAM usually leads to severe dimensional deviation between the as-built and the predesigned structures. This paper aims to propose a visual sensing technology and deep learning–assisted WAAM method for fabricating metallic structure, to simplify the complex WAAM process and improve the forming accuracy. Design/methodology/approach: Instead of slicing of the workpiece modeling and generating all the welding torch paths in advance of the fabricating process, this method is carried out by adding the feature point regression branch into the Yolov5 algorithm, to detect the feature point from the images of the as-built structure. The coordinates of the feature points of each deposition layer can be calculated automatically. Then the welding torch trajectory for the next deposition layer is generated based on the position of feature point. Findings: The mean average precision score of modified YOLOv5 detector is 99.5%. Two types of overhanging structures have been fabricated by the proposed method. The center contour error between the actual and theoretical is 0.56 and 0.27 mm in width direction, and 0.43 and 0.23 mm in height direction, respectively. Originality/value: The fabrication of circular overhanging structures without using the complicate slicing strategy, turning table or other extra support verified the possibility of the robotic WAAM system with deep learning technology. [ABSTRACT FROM AUTHOR]

Purpose: The metallic alloys and their components fabricated via laser powder bed fusion (LPBF) suffer from the microvoids formed inevitably due to the extreme solidification rate during fabrication, which are impossible to be removed by heat treatment. This paper aims to remove those microvoids in as-built AlSi10Mg alloys by hot forging and enhance their mechanical properties. Design/methodology/approach: AlSi10Mg samples were built using prealloyed powder with a set of optimized LPBF parameters, viz. 350 W of laser power, 1,170 mm/s of scan speed, 50 µm of layer thickness and 0.24 mm of hatch spacing. As-built samples were preheated to 430°C followed by immediate pressing with two different thickness reductions of 10% and 35%. The effect of hot forging on the microstructure was analyzed by means of X-ray diffraction, scanning electron microscopy, electron backscattered diffraction and transmission electron microscopy. Tensile tests were performed to reveal the effect of hot forging on the mechanical properties. Findings: By using hot forging, the large number of microvoids in both as-built and post heat-treated samples were mostly healed. Moreover, the Si particles were finer in forged condition (∼150 nm) compared with those in heat-treated condition (∼300 nm). Tensile tests showed that compared with heat treatment, the hot forging process could noticeably increase tensile strength at no expense of ductility. Consequently, the toughness (integration of tensile stress and strain) of forged alloy increased by ∼86% and ∼24% compared with as-built and heat-treated alloys, respectively. Originality/value: Hot forging can effectively remove the inevitable microvoids in metals fabricated via LPBF, which is beneficial to the mechanical properties. These findings are inspiring for the evolution of the LPBF technique to eliminate the microvoids and boost the mechanical properties of metals fabricated via LPBF. [ABSTRACT FROM AUTHOR]

Purpose: This paper aims to examine the static compression characteristics of cell topologies in body-centered cubic with vertical struts (BCCZ) and face-centered cubic with vertical struts (FCCZ) along with novel BCCZZ and FCCZZ lattice structures. Design/methodology/approach: The newly developed structures were obtained by adding extra interior vertical struts into the BCCZ and FCCZ configurations. The samples, composed of the AlSi10Mg alloy, were fabricated using the selective laser melting (SLM) additive manufacturing technique. The specific compressive strength and failure behavior of the manufactured lattice structures were investigated, and comparative analysis among them was done. Findings: The results revealed that the specific strength of BCCZZ and FCCZZ samples with 0.5 mm strut diameter exhibited approximately a 23% and 18% increase, respectively, compared with the BCCZ and FCCZ samples with identical strut diameters. Moreover, finite element analysis was carried out to simulate the compressive response of the lattice structures, which could be used to predict their strength and collapse mode. The findings showed that while the local buckling of lattice cells is the major failure mode, the samples subsequently collapsed along a diagonal shear band. Originality/value: An original and systematic investigation was conducted to explore the compression properties of newly fabricated lattice structures using SLM. The results revealed that the novel FCCZZ and BCCZZ structures were found to possess significant potential for load-bearing applications. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this study is to experimentally investigate the large deformation compression characteristics of fused deposition modelling (FDM)-printed poly lactic acid (PLA), considering the combined effect of infill density and strain rate, and to develop a constitutive viscoplastic model that can incorporate the infill density to predict the experimental result. Design/methodology/approach: The experimental approach focuses on strain rate-dependent (2.1 × 10−4, 2.1 × 10−3, and 2.1 × 10−2 s−1) compression testing for varied infill densities. Scanning electron microscopy (SEM) imaging of compressed materials is used to investigate deformation processes. A hyperelastic-viscoplastic constitutive model is constructed that can predict mechanical deformations at different strain rates and infill densities. Findings: The yield stress of PLA increased with increase in strain rate and infill density. However, higher degree of strain-softening response was witnessed for the strain rate corresponding to 2.1 × 10−2 s−1. While filament splitting and twisting were identified as the damage mechanisms at higher strain rates, matrix crazing was observed as the primary deformation mechanism for higher infill density (95%). The developed constitutive model captured yield stress and post-yield softening behaviour of FDM build PLA samples with a high R2 value of 0.99. Originality/value: This paper addresses the need to analyse and predict the mechanical response of FDM print polymers (PLA) undergoing extensive strain-compressive loading through a hyperelastic-viscoplastic constitutive model. This study links combined effects of the printing parameter (infill density) with the experimental parameter (strain rate). [ABSTRACT FROM AUTHOR]

Purpose: Auxetics metamaterials show high performance in their specific characteristics, while the absolute stiffness and strength are much weaker due to substantial porosity. This paper aims to propose a novel auxetic honeycomb structure manufactured using selective laser melting and study the enhanced mechanical performance when subjected to in-plane compression loading. Design/methodology/approach: A novel composite structure was designed and fabricated on the basis of an arrowhead auxetic honeycomb and filled with polyurethane foam. The deformation mechanism and mechanical responses of the structure with different structural parameters were investigated experimentally and numerically. With the verified simulation models, the effects of parameters on compression strength and energy absorption characteristics were further discussed through parametric analysis. Findings: A good agreement was achieved between the experimental and simulation results, showing an evidently enhanced compression strength and energy absorption capacity. The interaction between the auxetic honeycomb and foam reveals to exploit a reinforcement effect on the compression performance. The parametric analysis indicates that the composite with smaller included angel and higher foam density exhibits higher plateau stress and better specific energy absorption, while increasing strut thickness is undesirable for high energy absorption efficiency. Originality/value: The results of this study served to demonstrate an enhanced mechanical performance for the foam filled auxetic honeycomb, which is expected to be exploited with applications in aerospace, automobile, civil engineering and protective devices. The findings of this study can provide numerical and experimental references for the design of structural parameters. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this paper is to elucidate the extent to which the mechanisms of polymer melt viscous flow and finish layer powder particle adhesion influence the top surface topographies of laser sintered polyamide (PA12) components. Design/methodology/approach: Laser sintered specimens were manufactured at varying laser parameters in accordance with a full factorial design of experiments. Focus variation microscopy was used to ascertain insight into their top surface heights and peak/valley distributions. Subsequently, regression expressions were generated to model the former with respect to applied laser parameters. Auxiliary experimental analysis was also performed to validate the proposed mechanisms and statistical models. Findings: Within the parameter range tested, this work found the root mean square (Sq) and skewness (Ssk) roughness responses of laser sintered PA12 top surfaces to be inversely related to one another, and both also principally influenced by beam spacing. Furthermore, it was demonstrated that using optimised laser parameters (to promote polymer melt dispersion) and building without finish layers (to avert subsequent powder particle adhesion) reduced the mean Sq roughness of resultant topographies by 30.8% and 47.9% relative to standard laser sintered PA12 top surfaces, respectively. Practical implications: The scope to which laser sintered PA12 top surfaces can be modified was highlighted. Originality/value: This research demonstrated the impact the mechanisms of polymer melt viscous flow and finish layer powder particle adhesion have on laser sintered PA12 top surfaces. [ABSTRACT FROM AUTHOR]

Purpose: This paper aims to investigate the influence of post-curing temperature, post-curing time and gamma ray irradiation dose upon the tensile and compressive mechanical properties of the medical graded vat photopolymerization parts. Design/methodology/approach: Medical graded vat photopolymerization specimens, made from photopolymer resin, were fabricated using bottom-up vat photopolymerization machine. Tensile and compressive tests were conducted to assess the mechanical properties. The specimens were categorized into uncured and post-curing groups. Temperature post-processing and/or gamma irradiation exposure were for post-curing specimens. The post-curing parameters considered included temperature levels of 50°C, 60°C and 70°C, with 1, 2, 3 and 4 h periods. For the gamma irradiation, the exposure doses were 25, 50, 75 and 100 kGy. Findings: Post-curing improved the mechanical properties of medical graded vat photopolymerization parts for both tensile and compressive specimens. Post-curing temperature greater than 50°C or a prolonged post-curing period of more than 1 h made insignificant changes or deterioration in mechanical properties. The optimal post-curing condition was therefore a 50°C post-curing temperature with 1 h post-curing time. Exposure to gamma ray improved the compressive mechanical properties, but deteriorated tensile mechanical properties. Higher gamma irradiation doses could decrease the mechanical properties and also make the part more brittle, especially for doses more than 25 kGy. Originality/value: The obtained results would be beneficial to the medical device manufacturer who fabricated the invasive temporary contact personalized surgical instruments by vat photopolymerization technique. In addition, it also raised awareness in excessive gamma sterilization in the medical graded vat photopolymerization parts. [ABSTRACT FROM AUTHOR]

Purpose: This paper aims to study the design and characterization of a 3D printed tetrakaidecahedron cell-based acoustic metamaterial. At present, the mitigation of low-frequency noise involves the utilization of spatially demanding materials for the absorption of sound. These materials lack the ability for targeted frequency control adjustments. Hence, there is a requirement for an approach that can effectively manage low-frequency noise using lightweight and durable materials. Design/methodology/approach: The CAD model was created in SolidWorks and was manufactured using the Digital Light Processing (DLP) 3D printing technique. Experimental study and numerical simulations examined the metamaterial's acoustic absorption. An impedance tube with two microphones was used to determine the absorption coefficient of the metamaterial. The simulations were run in a thermoviscous module. Findings: The testing of acoustic samples highlighted the effects of geometric parameters on acoustic performance. Increment of the strut length by 0.4 mm led to a shift in response to a lower frequency by 500 Hz. Peak absorption rose from 0.461 to 0.690 as the strut diameter was increased from 0.6 to 1.0 mm. Increasing the number of cells from 8 to 20 increased the absorption coefficient and lowered the response frequency. Originality/value: DLP 3D printing technique was used to successfully manufacture tetrakaidecahedron-based acoustic metamaterial samples. A novel study on the effects of geometric parameters of tetrakaidecahedron cell-based acoustic metamaterial on the acoustic absorption coefficient was conducted, which seemed to be missing in the literature. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this paper is to provide a new procedure for in-plane compensation of geometric errors that often appear in the layers deposited by an additive manufacturing (AM) process when building a part, regardless of the complexity of the layer geometry. Design/methodology/approach: The procedure is based on comparing the real layer contours to the nominal ones extracted from the STL model of the part. Considering alignment and form deviations, the compensation algorithm generates new compensated contours that match the nominal ones as closely as possible. To assess the compensation effectiveness, two case studies were analysed. In the first case, the parts were not manufactured, but the distortions were simulated using a predictive model. In the second example, the test part was actually manufactured, and the distortions were measured on a coordinate measuring machine. Findings: The geometric deviations detected in both case studies, as evaluated by various quality indicators, reduced significantly after applying the compensation procedure, meaning that the compensated and nominal contours were better matched both in shape and size. Research limitations/implications: Although large contours showed deviations close to zero, dimensional overcompensation was observed when applied to small contours. The compensation procedure could be enhanced if the applied compensation factor took into account the contour size of the analysed layer and other geometric parameters that could have an influence. Originality/value: The presented method of compensation is applicable to layers of any shape obtained in any AM process. [ABSTRACT FROM AUTHOR]

Purpose: Radio frequency (RF) technology relies on the electromagnetic properties of the materials used, which includes their complex permittivities and loss tangents. To measure these properties, techniques for material characterization such as the transmission/reflection method are used in conjunction with conversion techniques to calculate these values from scattering parameters. Unfortunately, these techniques rely on relatively expensive rectangular waveguide adaptors and components, especially if testing over large frequency ranges. This paper aims to overcome this challenge by developing a more affordable test equipment solution based on additively manufactured waveguide sections. Design/methodology/approach: To evaluate the effectiveness of using additively manufactured waveguides to perform electromagnetic characterization with the transmission/reflection method, samples of PLA Tough with varying infill percentages and samples made from several Formlabs photopolymer resins are fabricated and analyzed. Findings: Results show that the method yielded permittivity and loss tangent values for the measured materials that generally agree with those found in the literature, supporting its credibility. Originality/value: The accessibility of this measurement technique will ideally allow for more electromagnetic material characterization to occur and expand the possible use of additive manufacturing in future RF designs. This work also provides characterization of several Formlabs photopolymer resins, which have not been widely analyzed in the current literature. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this paper is to design and manufacture an intelligent 3D printed sensor to monitor the re-occurrence of diaphragmatic hernia (DH; after surgery) in bovines as an Internet of Things (IOT)-based solution. Design/methodology/approach: The approach used in this study is based on a bibliographic analysis for the re-occurrence of DH in the bovine after surgery. Using SolidWorks and ANSYS, the computer-aided design model of the implant was 3D printed based on literature and discussions on surgical techniques with a veterinarian. To ensure the error-proof design, load test and strain–stress rate analyses with boundary distortion have been carried out for the implant sub-assembly. Findings: An innovative IOT-based additive manufacturing solution has been presented for the construction of a mesh-type sensor (for the health monitoring of bovine after surgery). Originality/value: An innovative mesh-type sensor has been fabricated by integration of metal and polymer 3D printing (comprising 17–4 precipitate hardened stainless steel and polyvinylidene fluoride-hydroxyapatite-chitosan) without sacrificing strength and specific absorption ratio value. [ABSTRACT FROM AUTHOR]

Purpose: This paper aims to evaluate the mechanical behaviour of polycarbonate/acrylonitrile butadiene styrene (PC/ABS) filaments for fusion filament fabrication (FFF). PC/ABS have emerged as a promising material for FFF due to their excellent mechanical properties. However, the optimal processing conditions and the effect of the blending ratio on the mechanical properties of the resulting workpieces are still unclear. Design/methodology/approach: A statistical factorial matrix was designed, including infill pattern, printing speed, nozzle size, layer height and printing temperature as factors (with three levels). A total of 810 workpieces were printed using PC/ABS blends filament with the FFF. The workpieces' finishing and mass were evaluated. Tensile tests were performed. Analysis of variance was performed to determine the main effects of the processing conditions on the mechanical properties. Findings: The results showed that the PC/ABS (70/30) exhibited higher tensile. Tensile rupture corresponded to 30% of the tensile strength. The infill pattern showed the highest contribution to the responses. The concentric pattern showed higher tensile strength. Tensile strength and mass ratio demonstrated the influence of mass on tensile strength. The influence of printing parameters on deformation depended on the blend proportions. Higher printing speed and lower layer height provided better quality workpieces. Originality/value: This study has implications for the design and manufacturing of three-dimensional printed parts using PC/ABS filaments. An extensive experimental matrix was applied, aiming at a complete understanding of mechanical behavior, considering the main printing parameters and combinations not explored by literature. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this paper is to assess the feasibility of analytical models, specifically the radial basis function method, Akbari–Ganji method and Gaussian method, in conjunction with the finite element method. The aim is to examine the impact of processing parameters on temperature history. Design/methodology/approach: Through analytical investigation and finite element simulation, this research examines the influence of processing parameters on temperature history. Simufact software with a thermomechanical approach was used for finite element simulation, while radial basis function, Akbari–Ganji and Gaussian methods were used for analytical modeling to solve the heat transfer differential equation. Findings: The accuracy of both finite element and analytical methods was validated with about 90%. The findings revealed direct relationships between thermal conductivity (from 100 to 200), laser power (from 400 to 800 W), heat source depth (from 0.35 to 0.75) and power absorption coefficient (from 0.4 to 0.8). Increasing the values of these parameters led to higher temperature history. On the other hand, density (from 7,600 to 8,200), emission coefficient (from 0.5 to 0.7) and convective heat transfer (from 35 to 90) exhibited an inverse relationship with temperature history. Originality/value: The application of analytical modeling, particularly the utilization of the Akbari–Ganji, radial basis functions and Gaussian methods, showcases an innovative approach to studying directed energy deposition. This analytical investigation offers an alternative to relying solely on experimental procedures, potentially saving time and resources in the optimization of DED processes. [ABSTRACT FROM AUTHOR]

Purpose: Limited geometric accuracy is one of the major challenges that hinder the wider application of additive manufacturing (AM). This paper aims to predict in-plane shape deviation for online inspection and compensation to prevent error accumulation and improve shape fidelity in AM. Design/methodology/approach: A sequence-to-sequence model with an attention mechanism (Seq2Seq+Attention) is proposed and implemented to predict subsequent layers or the occluded toolpath deviations after the multiresolution alignment. A shape compensation plan can be performed for the large deviation predicted. Findings: The proposed Seq2Seq+Attention model is able to provide consistent prediction accuracy. The compensation plan proposed based on the predicted deviation can significantly improve the printing fidelity for those layers detected with large deviations. Practical implications: Based on the experiments conducted on the knee joint samples, the proposed method outperforms the other three machine learning methods for both subsequent layer and occluded toolpath deviation prediction. Originality/value: This work fills a research gap for predicting in-plane deviation not only for subsequent layers but also for occluded paths due to the missing scanning measurements. It is also combined with the multiresolution alignment and change point detection to determine the necessity of a compensation plan with updated G-code. [ABSTRACT FROM AUTHOR]

Purpose: This paper aims to explore the growth of the South African additive manufacturing (AM) industry over the past 31 years through the lens of the innovation system (IS) perspective, examining the actor dynamics and mechanisms that facilitated or hindered the industry's development. Design/methodology/approach: The study used a case study research approach, analysing semi-structured interviews with eight South African AM experts and documentary evidence. The IS framework and the realist evaluation perspective were used, using a context-intervention-mechanism-outcome (CIMO)-based event history analysis (EHA) framework to explore the actor dynamics and mechanisms of the case study. Findings: The study used a case study research approach, analysing semi-structured interviews with eight South African AM experts and documentary evidence. The IS framework and the realist evaluation perspective were used, using a CIMO-based EHA framework to explore the actor dynamics and mechanisms of the case study. Originality/value: This paper contributes to the South African AM industry literature by providing an overview of the industry events over the past three decades and analysing the industry through the IS framework. The study is among the first to analyse the development of the South African AM industry, presenting innovation scholars and managers with valuable decision-making support by providing insights into the innovation activities performed during each stage of the industry's development, who performed them, the sequence in which they were performed and the outcomes they delivered. [ABSTRACT FROM AUTHOR]

Purpose: Three-dimensional (3D) printed parts usually have poor surface quality due to layer manufacturing's "stair casing/stair-stepping". So post-processing is typically needed to enhance its capabilities to be used in closed tolerance applications. This study aims to examine abrasive flow finishing for 3D printed polylactic acid (PLA) parts. Design/methodology/approach: A new eco-friendly abrasive flow machining media (EFAFM) was developed, using paper pulp as a base material, waste vegetable oil as a liquid synthesizer and natural additives such as glycine to finish 3D printed parts. Characterization of the media was conducted through thermogravimetric analysis and Fourier transform infrared spectroscopy. PLA crescent prism parts were produced via fused deposition modelling (FDM) and finished using AFM, with experiments designed using central composite design (CCD). The impact of process parameters, including media viscosity, extrusion pressure, layer thickness and finishing time, on percentage improvement in surface roughness (%ΔRa) and material removal rate were analysed. Artificial neural network (ANN) and improved grey wolf optimizer (IGWO) were used for data modelling and optimization, respectively. Findings: The abrasive media developed was effective for finishing FDM printed parts using AFM, with SEM images and 3D surface profile showing a significant improvement in surface topography. Optimal solutions were obtained using the ANN-IGWO approach. EFAFM was found to be a promising method for improving finishing quality on FDM 3D printed parts. Research limitations/implications: The present study is focused on finishing FDM printed crescent prism parts using AFM. Future research may be done on more complex shapes and could explore the impact of different materials, such as thermoplastics and composites for different applications. Also, implication of other techniques, such as chemical vapour smoothing, mechanical polishing may be explored. Practical implications: In the biomedical field, the use of 3D printing has revolutionized the way in which medical devices, implants and prosthetics are designed and manufactured. The biodegradable and biocompatible properties of PLA make it an ideal material for use in biomedical applications, such as the fabrication of surgical guides, dental models and tissue engineering scaffolds. The ability to finish PLA 3D printed parts using AFM can improve their biocompatibility, making them more suitable for use in the human body. The improved surface quality of 3D printed parts can also facilitate their sterilization, which is critical in the biomedical field. Social implications: The use of eco-friendly abrasive flow finishing for 3D printed parts can have a positive impact on the environment by reducing waste and promoting sustainable manufacturing practices. Additionally, it can improve the quality and functionality of 3D printed products, leading to better performance and longer lifespans. This can have broader economic and societal benefits. Originality/value: This AFM media constituents are paper pulp, waste vegetable oil, silicon carbide as abrasive and the mixture of "Aloe Barbadensis Mill" – "Cyamopsis Tetragonoloba" powder and glycine. This media was then used to finish 3D printed PLA crescent prism parts. The study also used an IGWO to optimize experimental data that had been modelled using an ANN. [ABSTRACT FROM AUTHOR]

Purpose: Timing constraints affect the manufacturing of traditional large-scale components through the material extrusion technique. Thus, researchers are exploring using many independent and collaborative heads that may work on the same part simultaneously while still producing an appealing final product. The purpose of this paper is to propose a simple and repeatable approach for toolpath planning for gantry-based n independent extrusion heads with effective collision avoidance management. Design/methodology/approach: This research presents an original toolpath planner based on existing slicing software and the traditional structure of G-code files. While the computationally demanding component subdivision task is assigned to computer-aided design and slicing software to build a standard G-code, the proposed algorithm scans the conventional toolpath data file, quickly isolates the instructions of a single extruder and inserts brief pauses between the instructions if the non-priority extruder conflicts with the priority one. Findings: The methodology is validated on two real-life industrial large-scale components using architectures with two and four extruders. The case studies demonstrate the method's effectiveness, reducing printing time considerably without affecting the part quality. A static priority strategy is implemented, where one extruder gets priority over the other using a cascade process. The results of this paper demonstrate that different priority strategies reflect on the printing efficiency by a factor equal to the number of extrusion heads. Originality/value: To the best of the authors' knowledge, this is the first study to produce an original methodology to efficiently plan the extrusion heads' trajectories for a collaborative material extrusion architecture. [ABSTRACT FROM AUTHOR]

Purpose: Demanding applications could benefit from the mathematical parametrization of lattice structures as this could lead not only to the characterization of structure–property relation but also facilitates the tailoring of the effective mechanical properties. This paper aims to characterize the mechanical performance of sine-based lattices. The characterization includes the results of in-plane Poisson's ratio plates models, and the stiffness of additively manufactured lattice plates when loaded in the out-of-plane direction, with the objective of obtaining a relation with their geometrical parameters. Design/methodology/approach: The geometrical parameter–Poisson's ratio relationship was characterized via finite element (FE) simulations. The stiffness was also measured on additively manufactured polylactic acid lattice plates and contrasted with FE computations. Findings: The characterization of auxetic lattice plates performed using in-plane and out-of-plane loading leads to key properties when deciding the geometry specific for applications: relative density, auxetic behavior and stiffness. Approximately 26% reduction of stiffness was observed between the square lattice and sine-based lattices of the same volume fraction. Originality/value: Auxetic metamaterials are potential candidates for applications in biomedical engineering, smart sensors, sports and soft robotics. This paper aims to contribute to the existing gap in the study of auxetic metamaterials subjected to complex loading conditions, other than simple tension and compression, required for the mentioned applications. [ABSTRACT FROM AUTHOR]

Purpose: This paper aims to investigate and deliver experimental evidence to establish ball burnishing (BB) as an effective procedure for processing fused filament fabricated parts (FFF). This study, which is a novel contribution to applying BB on FFF parts of materials with different properties, demonstrates the validity of this technology on polymers and provides generalizations for its implementation. Design/methodology/approach: A BB tool has been designed and validated. Statistical models have been used to determine the process parameters that provide the best results. In addition, the process' impacts on the dimensional accuracy, quality, hardness and mechanical performance of the treated parts under static bending and fatigue testing have been quantified and compared to the untreated samples. Findings: This study shows the best combination of process parameters for two printing orientations which have been decisive in obtaining successful results. These positive results allow stating procedure guidelines and recommendations for use in the industrial environment. Originality/value: This paper fulfills an identified need to enhance FFF parts' surface and mechanical properties, as more experimental evidence of studies demonstrating this technology's validity in additive manufacturing is yet to be found. [ABSTRACT FROM AUTHOR]

Purpose: This paper aims to address the development and implementation of "AltPrint," a slicing algorithm based on a new filling process planning from a variation in the deposited material geometry. AltPrint enables changes in the extruded material flow toward local variations in stiffness. The technical feasibility evaluation was conducted experimentally by fused filament fabrication (FFF) process of snap-fit subjected to a mechanical cyclical test. Design/methodology/approach: The methodology is based on the estimation of the parameter E from the mathematical relationships among the variation of the material in the material flow, nozzle geometry and extrusion parameters. Calibration, validation and analysis of the printed specimens were divided into two moments, of which the first refers to the material responses (flexural and dynamic mechanical analysis) and the second involves the analysis of the printed components with localized flow properties (for estimating the response to cyclic loading). Finite element analysis assisted in the comparison of two snap-fit geometries, one traditional and one generated by AltPrint. Finally, three examples of compliant mechanisms were developed to demonstrate the potential of the algorithm in the generation of functional prototypes. Findings: The contribution of AltPrint is the variable fill width integrated with the slicing software that varies the print parameters in different regions of the object. The alternative extrusion method based on material rate variation was conceived as an "open software" available in GitHub platform, hence, open manufacturing with initial focus on desktop 3D printer based on FFF. The slicing method provides deposited variable-width segments in an organized and replicable filling strategy, resulting in mechanical properties variations in specific regions of a part. It was implemented and evaluated experimentally and indicated potential applications in parts manufactured by the additive process based on extrusion, which requires local flexibilities. Originality/value: This paper presents a new alternative method for application in an open additive manufacturing context, specifically for additive extrusion techniques that enable local variations in the material flow. Its potential for manufacturing functional parts, which require flexibility due to cyclic loading, was demonstrated by fabrication and experimental evaluations of parts made in acrylonitrile butadiene styrene filament. The changes proposed by AltPrint enable geometric modifications in the response of the printed parts. The proposed slicing and filling control of parameters is inserted in a context of design for additive manufacturing and shows great potential in the area of product design. [ABSTRACT FROM AUTHOR]