Optimizing tensile strength and energy consumption for FDM through Mixed-Integer Nonlinear Multi-objective optimization and design of experiments

This study presents a methodology for optimizing key parameters of a fused deposition modeling (FDM) printer to minimize energy consumption (EC) while exceeding a specified tensile strength (TS) threshold. Employing Design of Experiments (DoE) with Taguchi and Response Surface analysis, we identify influential parameters affecting TS and EC. A Mixed-Integer Nonlinear Multi-Objective Optimization model is then utilized to balance TS and EC, resulting in optimal parameter values. Validation using fabricated specimens demonstrates less than 5 % error in Tensile Strength and less than 2 % error in Energy Consumption, confirming the efficacy of the proposed methodology.

3D and 4D Printing of PETG-ABS-Fe3O4 Nanocomposites with Supreme Remotely Driven Magneto-Thermal Shape-Memory Performance

This study introduces novel PETG-ABS-Fe3O4 nanocomposites that offer impressive 3D- and 4D-printing capabilities. These nanocomposites can be remotely stimulated through the application of a temperature-induced magnetic field. A direct granule-based FDM printer equipped with a pneumatic system to control the output melt flow is utilized to print the composites. This addresses challenges associated with using a high weight percentage of nanoparticles and the lack of control over geometry when producing precise and continuous filaments. SEM results showed that the interface of the matrix was smooth and uniform, and the increase in nanoparticles weakened the interface of the printed layers. The ultimate tensile strength (UTS) increased from 25.98 MPa for the pure PETG-ABS sample to 26.3 MPa and 27.05 MPa for the 10% and 15% Fe3O4 nanocomposites, respectively. This increase in tensile strength was accompanied by a decrease in elongation from 15.15% to 13.94% and 12.78%. The results of the shape-memory performance reveal that adding iron oxide not only enables indirect and remote recovery but also improves the shape-memory effect. Improving heat transfer and strengthening the elastic component can increase the rate and amount of shape recovery. Nanocomposites containing 20% iron oxide demonstrate superior shape-memory performance when subjected to direct heat stimulation and a magnetic field, despite exhibiting low print quality and poor tensile strength. Smart nanocomposites with magnetic remote-control capabilities provide opportunities for 4D printing in diverse industries, particularly in medicine, where rapid speed and remote control are essential for minimally invasive procedures.

The Impact of Plasma Surface Treatments on the Mechanical Properties and Magnetic Performance of FDM-Printed NdFeB/PA12 Magnets

This study presents a novel approach for improving the interfacial adhesion between Nd-Fe-B spherical magnetic powders and polyamide 12 (PA12) in polymer-bonded magnets using plasma treatments. By applying radio frequency plasma to the magnetic powder and low-pressure microwave plasma to PA12, we achieved a notable enhancement in the mechanical and environmental stability of fused deposition modeling (FDM)-printed Nd-Fe-B/PA12 magnets. The densities of the FDM-printed materials ranged from 92% to 94% of their theoretical values, with magnetic remanence (Br) ranging from 85% to 89% of the theoretical values across all batches. The dual plasma-treated batch demonstrated an optimal mechanical profile with an elastic modulus of 578 MPa and the highest ductility at 21%, along with a tensile strength range of 6 to 7 MPa across all batches. Flexural testing indicated that this batch also achieved the highest flexural strength of 15 MPa with a strain of 5%. Environmental stability assessments confirmed that applied plasma treatments did not compromise resistance to corrosion, evidenced by negligible flux loss in both hygrothermal and bulk corrosion tests. These results highlight plasma treatment's potential to enhance mechanical strength, magnetic performance, and environmental stability.

Improved Mechanical Performance in FDM Cellular Frame Structures through Partial Incorporation of Faces

The utilization of lattice-type cellular architectures has seen a significant increase, owing to their predictable shape and the ability to fabricate templated porous materials through low-cost 3D-printing methods. Frames based on atomic lattice structures such as face-centered cubic (FCC), body-centered cubic (BCC), or simple cubic (SC) have been utilized. In FDM, the mechanical performance has been impeded by stress concentration at the nodes and melt-solidification interfaces arising from layer-by-layer deposition. Adding plates to the frames has resulted in improvements with a concurrent increase in weight and hot-pocket-induced dimensional impact in the closed cells formed. In this paper, we explore compressive performance from the partial addition of plates to the frames of a SC-BCC lattice. Compression testing of both single unit cells and 4 × 4 × 4 lattices in all three axial directions is conducted to examine stress transfer to the nearest neighbor and assess scale-up stress transfer. Our findings reveal that hybrid lattice structure unit cells exhibit significantly improved modulus in the range of 125% to 393%, specific modulus in the range of 13% to 120%, and energy absorption in the range of 17% to 395% over the open lattice. The scaled-up lattice modulus increased by 8% to 400%, specific modulus by 2% to 107%, and energy absorption by 37% to 553% over the lattice frame. Parameters that emerged as key to improved lightweighting.

Numerical simulation of the flow of a tangent hyperbolic fluid over a stretching sheet within a porous medium, accounting for slip conditions

This study aims to explore the characteristics of tangent hyperbolic fluid flow along a stretching sheet. The sheet has suction or injection influences and is located inside a porous medium. The research inspects the flow and heat transfer (FHT) properties, taking into account the presence of a velocity slip condition. The flow of non-Newtonian magnetohydrodynamic fluid caused by a porous stretching sheet, taking into account thermal radiation and heat generation, has a wide range of engineering applications. These applications involve chemical reactors, energy distribution, storage of solar energy, and filtration processes. Mathematically, the flow problem is expressed as a collection of nonlinear partial differential equations. To numerically solve the resulting ODEs, the finite difference approach (FDM) is successfully used. Tables and graphs are used to display the various output values related to the hyperbolic tangent fluid. Among the different output values that appear are velocity and temperature. Significant observations from the study indicate that an increase in the power-law index, slip velocity parameter, porosity parameter, and magnetic number results in a decrease in the fluid's velocity and an increase in temperature. The completed comparison analysis shows a sizable degree of agreement with the earlier investigation.

Multi-Attribute Decision Making: Parametric Optimization and Modeling of the FDM Manufacturing Process Using PLA/Wood Biocomposites

The low carbon footprint, biodegradability, interesting mechanical properties, and relatively low price are considered some of the reasons for the increased interest in polylactic acid-based (PLA-based) filaments supplied with natural fillers. However, it is essential to recognize that incorporating natural fillers into virgin PLA significantly impacts the printability of the resulting blends. The complex inter-relationship between process, structure, and properties in the context of fused deposition modeling (FDM)-manufactured biocomposites is still not fully understood, which thus often results in decreased reliability of this technology in the context of biocomposites, decreased accuracy, and the increased presence of defects in the manufactured biocomposite samples. In light of these considerations, this study aims to identify the optimal processing parameters for the FDM manufacturing process involving wood-filled PLA biocomposites. This study presents an optimization approach consisting of Grey Relational Analysis in conjunction with the Taguchi orthogonal array. The optimization process has identified the combination of a scanning speed of 70 mm/s, a layer height of 0.1 mm, and a printing temperature of 220 °C as the most optimal, resulting in the highly satisfactory combination of good dimensional accuracy (Dx = 20.115 mm, Dy = 20.556 mm, and Dz = 20.220 mm) and low presence of voids (1.673%). The experimentally determined Grey Relational Grade of the specimen manufactured with the optimized set of process parameters (0.782) was in good agreement with the predicted value (0. 754), substantiating the validity of the optimization process. Additionally, the research compared the efficacy of optimization between the integrated multiparametric method and the conventional monoparametric strategy. The multiparametric method, which combines Grey Relational Analysis with the Taguchi orthogonal array, exhibited superior performance. Although the monoparametric optimization strategy yielded specimens with favorable values for the targeted properties, the analysis of the remaining characteristics uncovered unsatisfactory results. This highlights the potential drawbacks of relying on a singular optimization approach.

Optimization of Charpy Impact Strength of Tough PLA Samples Produced by 3D Printing Using the Taguchi Method

This research employs the Taguchi method and analysis of variance (ANOVA) to investigate, analyze, and optimize the impact strength of tough polylactic acid (PLA) material produced through fused deposition modeling (FDM). This study explores the effect of key printing parameters-specifically, infill density, raster angle, layer height, and print speed-on Charpy impact strength. Utilizing a Taguchi L16 orthogonal array experimental design, the parameters are varied within defined ranges. The results, analyzed through signal-to-noise (S/N) ratios and ANOVA, reveal that infill density has the most substantial impact on Charpy impact strength, followed by print speed, layer height, and raster angle. ANOVA identifies infill density and print speed as the most influential factors, contributing 38.93% and 36.51%, respectively. A regression model was formulated and this model predicted the impact strength with high accuracy (R2 = 98.16%). The optimized parameter set obtained through the Taguchi method, namely, a 100% infill density, 45/-45° raster angle, 0.25 mm layer height, and 75 mm/s print speed, enhances the impact strength by 1.39% compared to the experimental design, resulting in an impact strength of 38.54 kJ/m2. Validation experiments confirmed the effectiveness of the optimized parameters.

Shape Memory Effect of Four-Dimensional Printed Polylactic Acid-Based Scaffold with Nature-Inspired Structure

The four-dimensional (4D) printing is an evolving technology that has immense scope in various fields of science and technology owing to ever-challenging needs of human. It is an innovative upgradation of 3D printing procedure, which instills smart capabilities into materials such that they respond to external stimulus. This article aims to investigate the feasibility of 4D printing of polylactic acid (PLA)-based composite scaffolds fabricated by incorporating four different nature-inspired architectures (honeycomb, giant water lily, spiderweb, and nautilus shell). The composites were developed by adding 1, 3, and 5 wt.% of Calcium Phosphate (CaP) into PLA. Various thermomechanical tests were accomplished to evaluate the properties of developed material. Furthermore, the shape memory characteristics of these scaffolds were examined using thermally controlled conditions. The characterization tests displayed favorable outcomes in terms of thermal stability and hydrophilic nature of the PLA and PLA/CaP composite materials. It was found that the honeycomb structure showed the best shape memory and mechanical behavior among the four designs. Furthermore, the introduction of CaP was found to enhance mechanical strength and shape memory property, whereas the surface integrity was adversely affected. This study can play a vital role in developing self-fitting high-shape recovery biomedical scaffolds for bone-repair applications.

Preparation and Characterization of Composites Based on ABS Modified with Polysiloxane Derivatives

In this study, organosilicon compounds were used as modifiers of filaments constituting building materials for 3D printing technology. Polymethylhydrosiloxane underwent a hydrosilylation reaction with styrene, octadecene, and vinyltrimethoxysilane to produce new di- or tri-functional derivatives with varying ratios of olefins. These compounds were then mixed with silica and incorporated into the ABS matrix using standard processing methods. The resulting systems exhibited changes in their physicochemical and mechanical characteristics. Several of the obtained composites (e.g., modified with VT:6STYR) had an increase in the contact angle of over 20° resulting in a hydrophobic surface. The addition of modifiers also prevented a decrease in rheological parameters regardless of the amount of filler added. In addition, comprehensive tests of the thermal decomposition of the obtained composites were performed and an attempt was made to precisely characterize the decomposition of ABS using FT-IR and optical microscopy, which allowed us to determine the impact of individual groups on the thermal stability of the system.

Development of hybrid 3D printing approach for fabrication of high-strength hydroxyapatite bioscaffold using FDM and DLP techniques

This study develops a hybrid 3D printing approach that combines fused deposition modeling (FDM) and digital light processing (DLP) techniques for fabricating bioscaffolds, enabling rapid mass production. The FDM technique fabricates outer molds, while DLP prints struts for creating penetrating channels. By combining these components, hydroxyapatite (HA) bioscaffolds with different channel sizes (600, 800, and 1000μm) and designed porosities (10%, 12.5%, and 15%) are fabricated using the slurry casting method with centrifugal vacuum defoaming for significant densification. This innovative method produces high-strength bioscaffolds with an overall porosity of 32%-37%, featuring tightly bound HA grains and a layered surface structure, resulting in remarkable cell viability and adhesion, along with minimal degradation rates and superior calcium phosphate deposition. The HA scaffolds show hardness ranging from 1.43 to 1.87 GPa, with increasing compressive strength as the designed porosity and channel size decrease. Compared to human cancellous bone at a similar porosity range of 30%-40%, exhibiting compressive strengths of 13-70 MPa and moduli of 0.8-8 GPa, the HA scaffolds demonstrate robust strengths ranging from 40 to 73 MPa, paired with lower moduli of 0.7-1.23 GPa. These attributes make them well-suited for cancellous bone repair, effectively mitigating issues like stress shielding and bone atrophy.

Rice Husk with PLA: 3D Filament Making and Additive Manufacturing of Samples for Potential Structural Applications

Additive manufacturing has garnered significant attention as a versatile method for fabricating green and complex composite materials. This study delves into the fabrication of polymer composites by employing polylactic acid (PLA) in conjunction with rice husk as a reinforcing filler. The filaments were made by an extruded filament maker and then were used to make tensile and impact samples by another extrusion technology, fused deposition modeling (FDM). The structural and morphological characteristics of the composite materials were analyzed using scanning electron microscopy SEM. Results show that both the filament and samples are very reliable in producing polymer parts with this rice husk solid waste. This research contributes to increasing materials' circularity and potentially creating a local social economy around rice production, where this waste is not much used.

Flexural strength, flexural modulus and microhardness of milled vs. fused deposition modeling printed Zirconia; effect of conventional vs. speed sintering

BACKGROUND

Various methods can be used for creating zirconia dental restorations, including 3-dimensional (3D) printing and computer-aided design/ computer-aided manufacturing (CAD/CAM) milling. The fused deposition modeling (FDM) printing method for zirconia presents numerous advantages, albeit research on the mechanical properties of these materials and resultant restorations remains scarce. Such developments are undeniably intriguing and warrant further investigation. The objective of the present study was to evaluate the impact of the sintering firing cycle (Conventional vs. Speed sintering) on the flexural strength, flexural modulus, and Vickers Microhardness of milled vs. FDM printed zirconia.

METHODS

A total of 60 bars (2 × 5 × 27 mm) were fabricated for flexural strength testing, along with 40 discs (12 × 1.5 mm) for Vickers microhardness testing. Half of the specimens underwent conventional sintering, while the other half underwent a speed sintering cycle. The flexural strength and modulus were determined by a three-point bending test in a universal testing machine. The microhardness of the specimens was evaluated using a Vickers microhardness tester. Statistical analysis was performed using a two-way ANOVA test with a post-hoc Tukey test (p < 0.05).

RESULTS

CAD/CAM milled zirconia had significantly higher flexural strength and modulus than FDM-printed zirconia. The sintering process did not significantly affect the flexural strength or modulus of milled or FDM-printed zirconia. The milled speed sintering group had significantly higher values in the Vickers microhardness test compared to the other groups.

CONCLUSIONS

The mechanical properties of FDM-printed zirconia specimens were not found to be comparable to those of milled zirconia. Speed sintering cycle may produce milled zirconia restorations with similar flexural strength and modulus to conventional sintering, and even higher Vickers Microhardness values.

Application of xanthan and locust bean gum mix or sorbitol in the jelly formulation to improved jelly 3D printing using a fused deposition modeling printer

This study examined the impacts of applying a xanthan and locust bean gum mix or sorbitol to a jelly formulation on the rheological parameters necessary for 3D printing a jelly applying the fused deposition modeling method. A jelly formulation was fortified with a gum mix (xanthan gum:locust bean gum = 0.625:0.375) at 1% (w/w), or added with sorbitol instead of sugar. Both treatments increased the values of storage modulus and yield stress, related to fidelity and shape retention, and adding the gum mix, in particular, increased the gel strength. Applying these treatments to the formulation that lacks the rheological parameters and gel strength required for 3D printing changed those values in a direction fulfilling the material requirements. This research confirmed that the application of xanthan and locust bean gum mix or sorbitol could adjust the properties of materials used in 3D printing for improved printability.

Mechanical Characterisation of Bond Formation during Overprinting of PEEK Laminates

The latest generation of high-temperature 3D printers enables the production of complex structural components from aerospace-grade thermoplastics such as PEEK (polyether ether ketone). However, adding long or continuous fibres is currently limited, and thermal stresses introduced during the process restrict the maximum part dimensions. Combining 3D-printed components with continuous fibre-reinforced components into one hybrid structure has the potential to overcome such limitations. This work aims to determine whether in situ bonding between PEEK laminates and PEEK 3D printing during overprinting is feasible and which process parameters are significantly responsible for the bonding quality. To this end, the bonding is analysed experimentally in two steps. Firstly, the influence of the process parameters on the thermal history and the strength of the bond is investigated. In the second step, a detailed investigation of the most critical parameters is carried out. The investigation showed the feasibility of overprinting with bonding strengths of up to 15 MPa. It was shown that the bonding strength depends primarily on the temperature in the interface. Additionally, the critical parameters to control the process were identified. The process influences that were displayed form the basis for future hybrid component and process designs.

Design of Experiments to Compare the Mechanical Properties of Polylactic Acid Using Material Extrusion Three-Dimensional-Printing Thermal Parameters Based on a Cyber-Physical Production System

The material extrusion 3D printing process known as fused deposition modeling (FDM) has recently gained relevance in the additive manufacturing industry for large-scale part production. However, improving the real-time monitoring of the process in terms of its mechanical properties remains important to extend the lifespan of numerous critical applications. To enhance the monitoring of mechanical properties during printing, it is necessary to understand the relationship between temperature profiles and ultimate tensile strength (UTS). This study uses a cyber-physical production system (CPPS) to analyze the impact of four key thermal parameters on the tensile properties of polylactic acid (PLA). Layer thickness, printing speed, and extrusion temperature are the most influential factors, while bed temperature has less impact. The Taguchi L-9 array and the full factorial design of experiments were implemented along with the deposited line's local fused temperature profile analysis. Furthermore, correlations between temperature profiles with the bonding strength during layer adhesion and part solidification can be stated. The results showed that layer thickness is the most important factor, followed by printing speed and extrusion temperature, with very close influence between each other. The lowest impact is attributed to bed temperature. In the experiments, the UTS values varied from 46.38 MPa to 56.19 MPa. This represents an increase in the UTS of around 17% from the same material and printing design conditions but different temperature profiles. Additionally, it was possible to observe that the influence of the parameter variations was not linear in terms of the UTS value or temperature profiles. For example, the increase in the UTS at the 0.6 mm layer thickness was around four times greater than the increase at 0.4 mm. Finally, even when it was found that an increase in the layer temperature led to an increase in the value of the UTS, for some of the parameters, it could be observed that it was not the main factor that caused the UTS to increase. From the monitoring conditions analyzed, it was concluded that the material requires an optimal thermal transition between deposition, adhesion, and layer solidification in order to result in part components with good mechanical properties. A tracking or monitoring system, such as the one designed, can serve as a potential tool for reducing the anisotropy in part production in 3D printing systems.

Straightforward Design Strategy toward 3D Near-Net-Shape Stoichiometric SiC Parts

Fused deposition modeling (FDM), traditionally reserved for thermoplastics, is modified here with a granule-based extrusion head to be extended to advanced nonoxide ceramics via a straightforward design strategy that considers the shaping opportunities and the chemical richness offered by preceramic polymers. Specifically, 3D near-net-shape stoichiometric silicon carbide (SiC) objects are designed by manipulating the key features of a commercially available polycarbosilane (fusibility, high carbon content, relatively high SiC yield). In the early stage of the process, the carbon-rich polycarbosilane is first mixed with Si and SiC fillers and then thermolyzed at 120 °C to increase polymer branching while offering tailored rheological properties during the subsequent extrusion process at 90 °C and adequate shape retention once extruded. This allows for the design of tailored and complex 3D complex polycarbosilane-based architectures with features down to 400 µm. Polymer-based parts are further converted into 3D stoichiometric SiC objects with quasi-near-net-shape-a volume shrinkage reduced to 9.1% is measured-by heat treatment at a temperature as low as 1400 °C (argon flow). Given the flexibility to tune the preceramic polymer chemical and rheological properties, a new combined design approach is leveraged to generate bespoke advanced ceramics with a high freedom in geometry complexity.

Mass Reduction Techniques for Short Backfire Antennas: Additive Manufacturing and Structural Perforations

This paper presents novel approaches for reducing the mass of the classical short backfire (SBF) antenna by using additive manufacturing and structural perforations. We first investigated techniques to create a 3D-printed structure with a conductive coating material. This approach resulted in a significant mass reduction (70%) compared with the conventional metallic structure. We performed parametric simulation studies to investigate the effects of the manufacturing process and showed that there was practically no difference in the performance. The largest source of error was the surface roughness and the conductivity of the metal paint. In a second design, we created perforations in the structure to further reduce the mass. We performed parametric studies to optimize mass reduction and to characterize the effects of the perforations and the surface roughness introduced during the 3D-printing process on the antenna. Antenna prototypes were fabricated and tested. The masses of the perforated 3D printed antenna were approximately 30% and 20% of the original aluminum design, respectively (70% and 80% reductions in mass, respectively). The good agreement among the original design, simulation, and measurements demonstrated the effectiveness of the approach.

A Comprehensive Mechanical Examination of ABS and ABS-like Polymers Additively Manufactured by Material Extrusion and Vat Photopolymerization Processes

Additive manufacturing technologies have developed rapidly in recent decades, pushing the limits of known manufacturing processes. The need to study the properties of the different materials used for these processes comprehensively and in detail has become a primary goal in order to get the best out of the manufacturing itself. The widely used thermoplastic polymer material acrylonitrile butadiene styrene (ABS) was selected in the form of both filaments and ABS-like resins to investigate and compare the mechanical properties through a series of different tests. ABS-like resin material is commercially available, but it is not a sufficiently mechanically studied form of the material, which leads to the rather limited literature. Considering that ABS resin is a declared material that behaves like the ABS filament but in a different form, the objective of this study was to compare these two commercially available materials printed with three different 3D printers, namely Fused Deposition Modelling (FDM), Stereolithography (SLA) and Digital Light Processing (DLP). A total of 45 test specimens with geometries and test protocols conforming to the relevant standards were subjected to a series of tensile, three-point bending and compression tests to determine their mechanical properties. Characterization also included evaluation of morphology with 2D and 3D microscopy, dimensional accuracy of 3D scans, and Shore A hardness of each material and 3D printing process. Tensile testing results have shown that FDM toughness is 40% of the value for DLP. FDM elongation at break is 37% of DLP, while ultimate tensile stress for SLA is 27% higher than FDM value. Elastic modulus for FDM and SLA coincide. Flexure testing results indicate that value of DLP flexural modulus is 54% of the FDM value. SLA strain value is 59% of FDM, and DLP ultimate flexure stress is 77% of the value for FDM. Compression test results imply that FDM specimens absorb at least twice as much energy as vat polymerized specimens. Strain at break for SLA is 72% and strain at ultimate stress is 60% of FDM values. FDM yield stress is 32% higher than DLP value. SLA ultimate compressive stress is half of FDM, while value for DLP compressive modulus is 69% of the FDM value. The results obtained are beneficial and give a more comprehensive picture of the behavior of the ABS polymers used in different forms and different AM processes.

Progress of Polymer-Based Dielectric Composites Prepared Using Fused Deposition Modeling 3D Printing

Polymer-based dielectric composites are of great importance in advanced electronic industries and energy storage because of their high dielectric constant, good processability, low weight, and low dielectric loss. FDM (Fused Deposition Modeling) is a greatly accessible additive manufacturing technology, which has a number of applications in the fabrication of RF components, but the unavoidable porosity in FDM 3D-printed materials, which affects the dielectric properties of the materials, and the difficulty of large-scale fabrication of composites by FDM limit its application scope. This study's main focus is on how the matrix, filler, interface, and FDM 3D printing parameters influence the electrical properties of FDM-printed polymer-based dielectric composites. This review article starts with the fundamental theory of dielectrics. It is followed by a summary of the factors influencing dielectric properties in recent research developments, as well as a projection for the future development of FDM-prepared polymer-based dielectric composites. Finally, improving the comprehensive performance of dielectric composites is an important direction for future development.

Comparative Analysis of the Influence of Mineral Engine Oil on the Mechanical Parameters of FDM 3D-Printed PLA, PLA+CF, PETG, and PETG+CF Materials

Polymer materials and composites play a pivotal role in modern industry, prized for their durability, light weight, and resistance to corrosion. This study delves into the effects of mineral engine oil exposure on the mechanical parameters of 3D-printed materials created through fused deposition modeling (FDM). The research scrutinizes prototype materials under diverse environmental conditions, with a particular focus on the tensile parameters. The primary aim is to analyze and compare how mineral engine oil affects the mechanical parameters of four commonly used FDM 3D-printed materials: PLA, PLA+CF composites, PETG, and PETG+CF composites. In the case of the PLA specimens, the tensile strength decreased by approximately 36%, which, considering the 30% infill, remained acceptable. Simultaneously, the nominal strain at the point of breaking increased by 60.92% after 7 days and 47.49% after 30 days, indicating enhanced ductility. Interestingly, the PLA's Young's modulus remained unaffected by the oil. The 3D-printed PLA+CF materials exposed to 30 days of mineral engine oil displayed a substantial Young's modulus increase of over 49.93%. The PETG specimens exhibited intriguing behavior, with a tensile strength decrease of 16.66% after 7 days and 16.85% after 30 days, together with a notable increase in the nominal strain at breaking by 21.34% for 7 days and 14.51% for 30 days, signifying enhanced ductility. In PETG material specimens, the Young's modulus increased by 55.08% after 7 days and 66.27% after 30 days. The PETG+CF samples initially exhibited increases in tensile strength (1.78%) and nominal strain at breaking (6.08%) after 7 days, but later experienced an 11.75% reduction in the tensile strength after 30 days. This research underscores the critical role of material selection in oil-exposed environments and suggests avenues for future exploration, encompassing microstructural analysis, the long-term impact of oil exposure, and broader considerations related to environmental and oil-specific factors. It contributes to a deeper understanding of the intricate interactions between polymer materials and mineral engine oil, offering valuable insights that can enhance industrial applications.

Advanced Composite Materials Utilized in FDM/FFF 3D Printing Manufacturing Processes: The Case of Filled Filaments

The emergence of additive manufacturing technologies has brought about a significant transformation in several industries. Among these technologies, Fused Deposition Modeling/Fused Filament Fabrication (FDM/FFF) 3D printing has gained prominence as a rapid prototyping and small-scale production technique. The potential of FDM/FFF for applications that require improved mechanical, thermal, and electrical properties has been restricted due to the limited range of materials that are suitable for this process. This study explores the integration of various reinforcements, including carbon fibers, glass fibers, and nanoparticles, into the polymer matrix of FDM/FFF filaments. The utilization of advanced materials for reinforcing the filaments has led to the enhancement in mechanical strength, stiffness, and toughness of the 3D-printed parts in comparison to their pure polymer counterparts. Furthermore, the incorporation of fillers facilitates improved thermal conductivity, electrical conductivity, and flame retardancy, thereby broadening the scope of potential applications for FDM/FFF 3D-printed components. Additionally, the article underscores the difficulties linked with the utilization of filled filaments in FDM/FFF 3D printing, including but not limited to filament extrusion stability, nozzle clogging, and interfacial adhesion between the reinforcement and matrix. Ultimately, a variety of pragmatic implementations are showcased, wherein filled filaments have exhibited noteworthy benefits in comparison to standard FDM/FFF raw materials. The aforementioned applications encompass a wide range of industries, such as aerospace, automotive, medical, electronics, and tooling. The article explores the possibility of future progress and the incorporation of innovative reinforcement materials. It presents a plan for the ongoing growth and application of advanced composite materials in FDM/FFF 3D printing.

Research Status of and Prospects for 3D Printing for Continuous Fiber-Reinforced Thermoplastic Composites

Continuous fiber-reinforced thermoplastic composites (CFRTPCs) have advantages such as high specific strength, high specific modulus, corrosion resistance, and recyclability and are widely used in the fields of aerospace, rail transit, new energy, and so on. However, traditional methods for preparing CFRTPCs, such as placement and molding, rely more on forming molds, resulting in high manufacturing costs and a slow response speed, which limits the promotion and application of the new generation of CFRTPCs with complex configurations and designable performance. Three-dimensional printing can efficiently create products with multiple materials, complex structures, and integrated functions, introducing new ways and opportunities for the manufacturing of CFRTPCs. However, poor mechanical properties are the bottleneck problem in achieving 3D printing of CFRTPCs. This paper summarizes the research status of the fused deposition modeling (FDM) 3D printing process and the corresponding mechanical properties of CFRTPCs. The focus is on analyzing the influences of the FDM process parameters, such as the material type, printing temperature, speed parameters, layer thickness, scanning space, stacking direction, and fiber volume content, on the mechanical properties of CFRTPCs. Finally, the main problems and future prospects of current CFRTPCs-FDM are analyzed and forecasted, providing new references and ideas for 3D printing of high-performance CFRTPCs.

Numerical and experimental investigation on creep response of 3D printed Polylactic acid (PLA) samples. Part I: The effect of building direction and unidirectional raster orientation

The main aim of this research work is to investigate the effects of building directions and raster orientations on the creep behavior of 3D-printed plastic material and to develop rheological constitutive models to estimate the creep behavior of components. These components have been manufactured through the Fused Deposition Modeling (FDM) technique in which materials are heated and extruded through a nozzle to create 3D Polylactic acid (PLA) specimens. Since 3D-printed specimens exhibit anisotropic behavior, studying their building condition is necessary. Both building direction and raster orientation are among the fabrication conditions that play a major role in the mechanical behavior of the specimens. The tensile behavior of 3D-produced PLA specimens and their creep behavior were evaluated. To model the creep behavior of 3D printed PLA, three different types of rheological constitutive models, Zener, Burgers, and modified Burgers were used analytically and numerically. The finite element (FE) model of the 3D printed unnotched samples was developed to predict the creep behavior of notched samples. The results show that 3D FE models can predict the creep behavior of AM-notched specimens with high accuracy.

3D Printed Fused Deposition Modeling (FDM) Capillaries for Chemiresistive Gas Sensors

This paper discusses the possible use of 3D fused deposition modeling (FDM) to fabricate capillaries for low-cost chemiresistive gas sensors that are often used in various applications. The disadvantage of these sensors is low selectivity, but 3D printed FDM capillaries have the potential to increase their selectivity. Capillaries with 1, 2 and 3 tiers with a length of 1.5 m, 3.1 m and 4.7 m were designed and manufactured. Food and goods available in the general trade network were used as samples (alcohol, seafood, chicken thigh meat, acetone-free nail polish remover and gas from a gas lighter) were also tested. The "Vodka" sample was used as a standard for determining the effect of capillary parameters on the output signal of the MiCS6814 sensor. The results show the shift of individual parts of the signal in time depending on the parameters of the capillary and the carrier air flow. A three-tier capillary was chosen for the comparison of gas samples with each other. The graphs show the differences between individual samples, not only in the height of the output signal but also in its time characteristic. The tested 3D printed FDM capillaries thus made it possible to characterize the output response by also using an inexpensive chemiresistive gas sensor in the time domain.

Numerical Modeling of Mechanical Behavior of Functionally Graded Polylactic Acid-Acrylonitrile Benzidine Styrene Produced via Fused Deposition Modeling: Experimental Observations

Functionally graded materials (FGM) have attracted considerable attention in the field of composite materials and rekindled interest in research on composite materials due to their unique mechanical response achieved through material design and optimization. Compared to conventional composites, FGMs offer several advantages and exceptional properties, including improved deformation resistance, improved toughness, lightness properties, and excellent recoverability. This study focused on the production of functionally graded (FG) polymer materials by the additive manufacturing (AM) method. FG structures were produced by the fused deposition modeling (FDM) method using acrylonitrile benzidine styrene (ABS) and polylactic acid (PLA) materials, and tensile tests were performed according to ASTM D638. The effects of different layer thicknesses, volume ratios, and total thicknesses on mechanical behavior were investigated. The tensile standard of materials produced by additive manufacturing introduces geometric differences. Another motivation in this study is to reveal the differences between the results according to the ASTM standard. In addition, tensile tests were carried out by producing single-layer samples at certain volume ratios to create a numerical model with the finite element method to verify the experimental data. As a result of this study, it is presented that the FG structure produced with FDM improves mechanical behavior.

Overview and Comparison of PLA Filaments Commercially Available in Europe for FFF Technology

This study presents a comprehensive techno-economic analysis of PLA materials for fused filament fabrication (FFF) from eight European manufacturers. The comparison involved rigorous experimental assessments of the mechanical properties, dimensional accuracy, and print quality using standardized methods and equipment such as tensile and CT testing. What makes this study unique is the consistent methodology applied, considering factors such as material color, printing temperature, printing orientation, filament diameter, and printer selection, to ensure meaningful and reliable results. Contrary to the common belief that a higher price implies better quality, the study revealed that the second cheapest PLA material achieved the best overall performance within the methodology employed. The study also confirmed certain observations, such as the influence of printing orientation and geometry on dimensional accuracy and mechanical properties, as well as the significant disparities between manufacturer-provided values and actual measured mechanical properties, highlighting the importance of experimental verification. Hence, the findings of this study hold value not only for the scientific community but also for hobbyist printers and beginners in the 3D printing realm seeking guidance in material selection for their projects. Furthermore, the methodology employed in this research can be adapted for evaluating a broad range of other 3D printing materials.

Additive Manufacturing Using Agriculturally Derived Biowastes: A Systematic Literature Review

Agriculturally derived biowastes can be transformed into a diverse range of materials, including powders, fibers, and filaments, which can be used in additive manufacturing methods. This review study reports a study that analyzes the existing literature on the development of novel materials from agriculturally derived biowastes for additive manufacturing methods. A review was conducted of 57 selected publications since 2016 covering various agriculturally derived biowastes, different additive manufacturing methods, and potential large-scale applications of additive manufacturing using these materials. Wood, fish, and algal cultivation wastes were also included in the broader category of agriculturally derived biowastes. Further research and development are required to optimize the use of agriculturally derived biowastes for additive manufacturing, particularly with regard to material innovation, improving print quality and mechanical properties, as well as exploring large-scale industrial applications.

Optimization of Printing Parameters to Enhance Tensile Properties of ABS and Nylon Produced by Fused Filament Fabrication

This study aimed to identify the optimum printing parameters for the fused filament fabrication (FFF) of acrylonitrile butadiene styrene (ABS) and polyamide (nylon), to improve strength properties. For this purpose, the methodology of the paper involves an experimental study that used Taguchi's method to identify the effects of the infill pattern, infill density, and printing speed on the mechanical properties of the materials. ABS and nylon plastic parts were tested in tension to failure. Based on the results of the tensile tests, it was found that ABS material produced the highest ultimate tensile strength when printed using a tri-hexagonal infill pattern, 100% infill density, and a printing speed of 65 mm/s. On the other hand, nylon material exhibited a better performance when printed using an octet geometric structure, with identical other parameters.

Elemental and experimental analysis of modified stent's structure under uniaxial compression load

Additive manufacturing has enabled the fabrication of lightweight complex metamaterials that possess high energy absorption and impact resistance properties. Stents, a typical 3D auxetic material, have significant self-expanding behavior, and their mechanical properties can be finely tuned over a wide range. In this study, we systematically analyzed three distinctive elastic-plastic regions using experimental, numerical simulations, and theoretical analysis, focusing on investigating the energy absorption capability of a designed structure by varying tessellated unit cell numbers in two section views in X- and Y-direction. Two batches of 5 specimens each were 3D printed using FDM techniques. The results showed that designing a self-expanding stent with innovative capabilities was possible, with the yield stress ranging between 1.5 MPa and 2.0 MPa and extended effective elastic moduli derived from the deformation mode of tessellated unit cells. The maximum energy absorption for all structures ranged between 7.1J and 18J, with similar capabilities observed for the designed stents. However, increasing unit cells along the X-direction resulted in a significant increase in SEA, while the Y-direction remained unchanged. Therefore, these structures have a significant influence on areas requiring energy absorption. In addition, they are the ideal class of energy absorbers for cushioning applications. Furthermore, their energy-absorption capacity can be easily tailored to meet specific end-use requirements by varying their structural parameters using unit cell tessellation.

The 3D-Printed (FDM/FFF) Biocomposites Based on Polylactide and Carbonate Lake Sediments-Towards a Circular Economy

In this study, composites containing polylactide and carbonate lake sediment in concentrations of 2.5, 5, 10, and 15% by weight were prepared by a 3D printing method. The material for 3D printing was obtained by directly diluting the masterbatch on an injection moulder to the desired concentrations, and after granulation, it was extruded into a filament. The material prepared thusly was used to print standardised samples for mechanical testing. To compare the mechanical properties of the composites obtained by 3D printing and injection moulding, two sets of tests were performed, i.e., mechanical tests (tensile strength, flexural strength, and impact strength) and hydrophobic-hydrophilic surface character testing. The degree of composite waste in the 3D printing was also calculated. Mechanical and surface tests were performed for both systems conditioned at room temperature and after accelerated ageing in a weathering chamber. The study showed differences in the properties of composites obtained by 3D printing. Sedimentary fillers improved the hydrophobicity of the systems compared with pure PLA, but it was not a linear relationship. The PLA/CLS sedB composite had higher strength parameters, especially after ageing in a weathering chamber. This is due to its composition, in which, in addition to calcite and silica, there are also aluminosilicates, causing a strengthening of the PLA matrix.

Investigation of the Manufacturing Orientation Impact on the Mechanical Properties of Composite Fiber-Reinforced Polymer Elements in the Fused Filament Fabrication Process

This article examines the mechanical properties and compatibility of selected composite materials produced with RP technology and the FFF-fused filament fabrication process. The article scales sophisticated modern materials based on PLA-polylactic acid-plastic and its composite variants. The research is carried out on the 3D FFF printer Felix 3.1 with a dual extruder, which works on the "open-source" principle. In this research, elements of the paradigm and methodology of the processing technology for RP were applied; they were implemented according to EN ISO 527 and ISO 2602 standards. The aim of this study was to investigate the impact of 3D-printing strategy on the mechanical properties of 5 types of PLA composites. The results of this research solve the material compatibility problem, primarily through experimental testing of different combinations of filaments in different printing directions. Analysis of the experimental data showed correlations between the choice of printing strategy and mechanical properties, mainly tensile strength of the selected filaments. The research results show the influence of the printing orientation on mechanical properties of 3D printed samples: parts extruded in length orientation showed higher values of tensile strength compared to parts made in width and height. The CarbonPLA material exhibited 10 times higher tensile strength when printed in length compared to samples.

Cells-in-Touch: 3D Printing in Reconstruction and Modelling of Microscopic Biological Geometries for Education and Future Research Applications

Additive manufacturing (3D printing) and computer-aided design (CAD) still have limited uptake in biomedical and bioengineering research and education, despite the significant potential of these technologies. The utility of organ-scale 3D-printed models of living structures is widely appreciated, while the workflows for microscopy data translation into tactile accessible replicas are not well developed yet. Here, we demonstrate an accessible and reproducible CAD-based methodology for generating 3D-printed scalable models of human cells cultured in vitro and imaged using conventional scanning confocal microscopy with fused deposition modeling (FDM) 3D printing. We termed this technology CiTo-3DP (Cells-in-Touch for 3D Printing). As a proof-of-concept, we created dismountable CiTo-3DP models of human epithelial, mesenchymal, and neural cells by using selectively stained nuclei and cytoskeletal components. We also provide educational and research context for the presented cellular models. In the future, the CiTo-3DP approach can be adapted to different imaging and 3D printing modalities and comprehensively present various cell types, subcellular structures, and extracellular matrices. The resulting CAD and 3D printed models could be used for a broad spectrum of education and research applications.

Combinatorial 3D printed dosage forms for a two-step and controlled drug release

Fused deposition modeling (FDM) and selective laser sintering (SLS) are two of the most employed additive manufacturing (AM) techniques within the pharmaceutical research field. Despite the numerous advantages of different AM methods, their respective drawbacks have yet to be fully addressed, and therefore combinatorial systems are starting to emerge. In the present study, hybrid systems comprising SLS inserts and a two-compartment FDM shell are developed to achieve controlled release of the model drug theophylline. Via the use of SLS a partial amorphization of the drug is demonstrated, which can be advantageous in the case of poorly soluble drugs, and it is shown that sintering parameters can regulate the dosage and release kinetics of the drug from the inserts. Furthermore, via different combinations of inserts within the FDM-printed shell, various drug release patterns, such as a two-step or prolonged release, can be achieved. The study serves as a proof of concept, highlighting the advantages of combining two AM techniques, both to overcome their respective shortcomings and to develop modular and highly tunable drug delivery devices.

An investigation of combined effect of infill pattern, density, and layer thickness on mechanical properties of 3D printed ABS by fused filament fabrication

Additive manufacturing technology and its benefits have a significant impact on different industrial applications. The 3D printing technologies help manufacture lightweight intricate geometrical designs with enhanced strengths. The present study investigates the blended effects of previously recommended parameters of different infill patterns (line, triangle, and concentric) and infill densities (75, 80, and 85%) with varying thicknesses of layers (100, 200, and 300 μm). The test samples were created through Fused Filament Fabrication (FFF) technology using Acrylonitrile Butadiene Styrene (ABS) 3D printing. Mechanical properties were evaluated through tensile and impact strength tests conducted in accordance with ASTM standards. The experimental investigation reveals that the infill pattern greatly affected both tensile and impact strength. The best results were obtained with a concentric infill pattern, along with 80% infill density and 100 μm layer thickness. These conditions resulted in 123% and 115% higher tensile strength and 168% and 80% higher impact strength compared to line and triangle patterns, respectively.

Possibilities of Using Selected Additive Methods for the Production of Polymer Harmonic Drive Prototypes

This article includes an analysis of the possibility of using polymer materials for the production of harmonic drive. The use of additive methods greatly eases and accelerates the manufacturing of the flexspline. In the case of gears made of polymeric materials using rapid prototyping (RP) methods, the problem is often with their mechanical strength. In a harmonic drive, the wheel is uniquely exposed to damage, because during work, it deforms and is additionally loaded with torque. Therefore, numerical calculations were conducted using the finite element method (FEM) in the Abaqus program. As a result, information was obtained on the distribution of stresses in the flexspline and their maximum values. On this basis, it was possible to determine whether a flexspline made of specific polymers could be used in commercial harmonic drives or whether they were only adequate for the production of prototypes.

The Effects of Self-Polymerized Polydopamine Coating on Mechanical Properties of Polylactic Acid (PLA)-Kenaf Fiber (KF) in Fused Deposition Modeling (FDM)

This research examines the impact of self-polymerized polydopamine (PDA) coating on the mechanical properties and microstructural behavior of polylactic acid (PLA)/kenaf fiber (KF) composites in fused deposition modeling (FDM). A biodegradable FDM model of natural fiber-reinforced composite (NFRC) filaments, coated with dopamine and reinforced with 5 to 20 wt.% bast kenaf fibers, was developed for 3D printing applications. Tensile, compression, and flexural test specimens were 3D printed, and the influence of kenaf fiber content on their mechanical properties was assessed. A comprehensive characterization of the blended pellets and printed composite materials was performed, encompassing chemical, physical, and microscopic analyses. The results demonstrate that the self-polymerized polydopamine coating acted as a coupling agent, enhancing the interfacial adhesion between kenaf fibers and the PLA matrix and leading to improved mechanical properties. An increase in density and porosity was observed in the FDM specimens of the PLA-PDA-KF composites, proportional to their kenaf fiber content. The enhanced bonding between kenaf fiber particles and the PLA matrix contributed to an increase of up to 13.4% for tensile and 15.3% for flexural in the Young's modulus of PLA-PDA-KF composites and an increase of up to 30% in compressive stress. The incorporation of polydopamine as a coupling agent in the FDM filament composite led to an improvement in tensile, compressive, and flexural stresses and strain at break, surpassing that of pure PLA, while the reinforcement provided by kenaf fibers was enhanced more by delayed crack growth, resulting in a higher strain at break. The self-polymerized polydopamine coatings exhibit remarkable mechanical properties, suggesting their potential as a sustainable material for diverse applications in FDM.

Poly(3-hydroxybutyrate) (PHB) and Polycaprolactone (PCL) Based Blends for Tissue Engineering and Bone Medical Applications Processed by FDM 3D Printing

In the presented work, poly(3-hydroxybutyrate)-PHB-based composite blends for bone medical applications and tissue engineering are prepared and characterized. PHB used for the work was in two cases commercial and, in one case, was extracted by the chloroform-free route. PHB was then blended with poly(lactic acid) (PLA) or polycaprolactone (PCL) and plasticized by oligomeric adipate ester (Syncroflex, SN). Tricalcium phosphate (TCP) particles were used as a bioactive filler. Prepared polymer blends were processed into the form of 3D printing filaments. The samples for all the tests performed were prepared by FDM 3D printing or compression molding. Differential scanning calorimetry was conducted to evaluate the thermal properties, followed by optimization of printing temperature by temperature tower test and determination of warping coefficient. Tensile test, three-point flexural test, and compression test were performed to study the mechanical properties of materials. Optical contact angle measurement was conducted to determine the surface properties of these blends and their influence on cell adhesion. Cytotoxicity measurement of prepared blends was conducted to find out whether the prepared materials were non-cytotoxic. The best temperatures for 3D printing were 195/190, 195/175, and 195/165 °C for PHB-soap/PLA-SN, PHB/PCL-SN, and PHB/PCL-SN-TCP, respectively. Their mechanical properties (strengths ~40 MPa, moduli ~2.5 GPa) were comparable with human trabecular bone. The calculated surface energies of all blends were ~40 mN/m. Unfortunately, only two out of three materials were proven to be non-cytotoxic (both PHB/PCL blends).

The Mechanical Properties of Thin-Walled Specimens Printed from a Bronze-Filled PLA-Based Composite Filament Using Fused Deposition Modelling

This article focuses on the mechanical property analysis of important models omitted in many scientific papers (thin-walled specimens) printed from innovative material-such as PLA + bronze composite-using fused deposition modelling technology. It discusses the printing process, the measurement of the specimen geometry, the static tensile strength tests and the microscopic examinations conducted with a scanning electron microscope. The findings of this study could be used as an input to further research into the accuracy of filament deposition and the modification of base materials with bronze powder and for the optimization of the machine design, e.g., with the use of cell structures. The experimental results indicated that the thin-walled models fabricated using FDM showed substantial differences in tensile strength, depending on the specimen's thickness and the printing orientation. It was shown that it was not possible to test thin-walled models located on the building platform along the Z axis due to the lack of sufficient adhesion between the layers.

New Partially Water-Soluble Feedstocks for Additive Manufacturing of Ti6Al4V Parts by Material Extrusion

In this work, a process chain for the realization of dense Ti6Al4V parts via different material extrusion methods will be introduced applying eco-friendly partially water-soluble binder systems. In continuation of earlier research, polyethylene glycol (PEG) as a low molecular weight binder component was combined either with poly(vinylbutyral) (PVB) or with poly(methylmethacrylat) (PMMA) as a high molecular weight polymer and investigated with respect to their usability in FFF and FFD. The additional investigation of different surfactants' impact on the rheological behaviour applying shear and oscillation rheology allowed for a final solid Ti6Al4V content of 60 vol%, which is sufficient to achieve after printing, debinding and thermal densification parts with densities better than 99% of the theoretical value. The requirements for usage in medical applications according to ASTM F2885-17 can be fulfilled depending on the processing conditions.

Design and Characterization of Baricitinib Incorporated PLA 3D Printed Pills by Fused Deposition Modeling: An Oral Pill for Treating Alopecia Areata

This study aimed to develop three-dimensional (3D) baricitinib (BAB) pills using polylactic acid (PLA) by fused deposition modeling. Two strengths of BAB (2 and 4% w/v) were dissolved into the (1:1) PEG-400 individually, diluting it with a solvent blend of acetone and ethanol (27.8:18:2) followed by soaking the unprocessed 200 cm~6157.94 mg PLA filament in the solvent blend acetone-ethanol. FTIR spectrums of the 3DP1 and 3DP2 filaments calculated and recognized drug encapsulation in PLA. Herein, 3D-printed pills showed the amorphousness of infused BAB in the filament, as indicated by DSC thermograms. Fabricated pills shaped like doughnuts increased the surface area and drug diffusion. The releases from 3DP1 and 3DP2 were found to be 43.76 ± 3.34% and 59.14 ± 4.54% for 24 h. The improved dissolution in 3DP2 could be due to the higher loading of BAB due to higher concentration. Both pills followed Korsmeyer-Peppas' order of drug release. BAB is a novel JAK inhibitor that U.S. FDA has recently approved to treat alopecia areata (AA). Therefore, the proposed 3D printed tablets can be easily fabricated with FDM technology and effectively used in various acute and chronic conditions as personalized medicine at an economical cost.

Study of dose dependence on density in planar 3D-printed applicators for HDR Ir192 surface brachytherapy

PURPOSE

This paper describes a method to evaluate the influence of 3D printed plesiotherapy applicators densities in the most clinically relevant dosimetric planes of these brachytherapy treatments. Studied densities range goes from that of water to that of air including the intermediate applicators densities made of acrylonitrile butadiene styrene and polylactic acid, materials used as Fused Deposition Modelling (FDM) filaments.

METHODS AND MATERIALS

All applicators were manufactured by means of FDM 3D printing and a special empty applicator of ABS walls was designed to be filled with water or air. In each of these applicators, the values of the dose and gamma index at the surface and at the prescription depth were measured in clinical conditions, using EBT films.

RESULTS

Analysis of results allow us to conclude that the influence of the applicators density on the dose value in the studied materials depends on the distance at which the dose is measured. Thus, at the prescription depth no influence is observed, however this influence becomes noticeable near the surface of the applicators with dose differences of more than 10% for densities close to 0.4 g/cm³.

CONCLUSION

Therefore, the density of FDM manufactured applicators should be taken into account when calculating surface dose for low density applicators, as variations caused by density can have clinical implications because is the surface dose that is associated with the toxicity of brachytherapy skin treatments.

Adjusting Surface Models of Cellular Structures for Making Physical Models Using FDM Technology

In the planning stage of the fabrication process of physical models of cellular structures, a surface model of the structure needs to be adjusted to acquire the requisite properties, but errors emerge frequently at this stage. The main objective of this research was to repair or reduce the impact of deficiencies and errors before the fabrication of physical models. For this purpose, it was necessary to design models of cellular structures with different accuracy settings in PTC Creo and then compare them after the tessellation process using GOM Inspect. Subsequently, it was necessary to locate the errors occurring in the process of preparing models of cellular structures and propose an appropriate method of their repair. It was found that the Medium Accuracy setting is adequate for the fabrication of physical models of cellular structures. Subsequently, it was found that within regions where mesh models merged, duplicate surfaces emerged, and the entire model could be considered as manifesting non-manifold geometry. The manufacturability check showed that in the regions with duplicate surfaces inside the model, the toolpath creation strategy changed, causing local anisotropy within 40% of the fabricated model. A non-manifold mesh was repaired in the proposed manner of correction. A method of smoothing the model's surface was proposed, reducing the polygon mesh density and the file size. The findings and proposed methods of designing cellular models, error repair and smoothing methods of the models can be used to fabricate higher-quality physical models of cellular structures.

Fused Deposition Modelling of Polymeric Auxetic Structures: A Review

Additive Manufacturing (AM) techniques have recently attracted the attention of scientists for the development of prototypes with complex or particular geometry in a fast and cheap way. Among the different AM processes, the Fused Deposition Modelling process (FDM) offers several advantages in terms of costs, implementation features and design freedom. Recently, it has been adopted to realise auxetic structures, which are characterised by negative Poisson ratio, enhanced mechanical properties, and a higher compression resistance than conventional structures. This review outlines the use of AM processes, in particular FDM, to design and obtain auxetic structures, with the final aim to exploit their applications in different fields. The first part of this work presents a brief classification of auxetic structures and materials. Subsequently, a summary of additive manufacturing processes is presented, focusing on the use of FDM and its limitations. Finally, the studies on the use of additive manufacturing to produce auxetic structures are shown, evidencing the potential of the concurrent combination of a fast prototyping technique such as FDM and the characteristics of polymer- and/or composite-based auxetic structures. Indeed, this new technological field opens the possibility of realising novel structures with integrated smart behaviour, multifunctional properties, compression resistance, and a tailored microstructure and shape.

Bioresorbable PPDO sliding-lock stents with optimized FDM parameters for congenital heart disease treatment

Stent implantation has been a promising therapy for congenital heart disease (CHD) due to better efficacy. Compared to permanent metal stents, bioresorbable polymer stents have shown a great advantage in accommodating the vascular growth of pediatric patients, but the application is still limited due to inferior radial strength. Here, bioresorbable poly(p-dioxanone) (PPDO) sliding-lock stents for CHD treatment were fabricated by fused deposition modeling (FDM). The effects of FDM processing parameters, including nozzle temperature, bed temperature, layer thickness, and printing speed, on the mechanical properties of PPDO parts were investigated to optimize the processing condition to enhance the radial strength of stents. Finite element analysis (FEA) was also used to evaluate the mechanical properties of stents. PPDO sliding-lock stents fabricated under optimized FDM parameters showed radial strength of 3.315 ± 0.590 N/mm, superior to benchmark commercial metal stents. Radial strength curve and compression behavior of PPDO sliding-lock stents were investigated. Results of FEA exhibited that strut width, shape of the mesh cell and surface coverage ratio had an impact on the compression force of PPDO sliding-lock stents. PPDO sliding-lock stents fabricated with optimized FDM parameters show favorable mechanical performance and meet the requirement of CHD treatment.

Additive manufacturing of PLA-Mg composite scaffolds for hard tissue engineering applications

Polylactic acid (PLA) is considered as a great option to be employed as 3D porous scaffold in hard tissue engineering applications owing to its excellent biocompatibility and processability. However, relatively weak mechanical properties and inappropriate biodegradability limit its extensive usage. In order to overcome the mentioned challenges, micrometric magnesium particles were incorporated into the PLA matrix by the fused deposition modeling (FDM) technique. The effects of various Mg contents (i.e., 2, 4, 6, 8 and 10 wt%) on the structural, thermal, rheological, mechanical, wettability, degradability characteristics and cellular behavior of the 3D porous PLA-Mg composite scaffolds were examined. The developed PLA-Mg composites exhibit an interconnected porous structure with a mostly uniform distribution of Mg particles in the PLA matrix. It was found that incorporation of Mg particles into the PLA matrix enhances the mechanical, physical, chemical and biological characteristics of PLA. The cell studies demonstrate that the PLA-6Mg composite scaffold provides the best cellular response in terms of cell atachment and viability. The obtained results in this investigation greatly suggest that the 3D-printed PLA-Mg composite scaffold is a promising candidate for hard tissue engineering applications.

Energy Recovery from Polymeric 3D Printing Waste and Olive Pomace Mixtures via Thermal Gasification-Effect of Temperature

One of the polymeric materials used in the most common 3D printers is poly(ethylene terephthalate) glycol (PETG). It represents, in world terms, around 2.3% of polymeric raw material used in additive manufacturing. However, after processing this material, its properties change irreversibly. A significant amount of waste is produced around the world, and its disposal is usually destined for landfill or incineration, which can generate an important issue due to the high environmental risks. Polymer waste from 3D printing, hereinafter 3DPPW, has a relatively high calorific value and adequate characteristics to be valued in thermochemical processes. Gasification emerges as an innovative and alternative solution for recovering energy from 3DPPW, mixed with residues of lignocellulosic origin, and presents some environmental advantages compared to other types of thermochemical treatments, since the gasification process releases smaller amounts of NOx into the atmosphere, SOx, and CO₂. In the case of the study, co-gasification of olive pomace (OLB) was carried out with small additions of 3DPPW (10% and 20%) at different temperatures. Comparing the different gasifications (100% OLB, 90% OLB + 10% 3DPPW, 80% OLB + 20% 3DPPW), the best results for the synthesis gas were obtained for the mixture of 10% 3DPPW and 90% olive pomace (OLB), having a lower calorific value of 6.16 MJ/m³, synthesis gas yield of 3.19%, and cold gas efficiency of 87.85% for a gasification temperature of 750 °C. In addition, the results demonstrate that the addition of 3DPPW improved the quality of syngas, especially between temperatures of 750 and 850 °C. Including polymeric 3D printing materials in the context of the circular economy and extending their life cycle helps to improve the efficiency of subsequent industrial processes, reducing process costs in general, thanks to the new industrial value acquired by the generated by-products.

A combination of FDM, EWM, and GRA to measure performance in higher vocational college: An empirical case from China

Given the problems of unclear division of evaluation factors, inadequate utilization of objective data and unreasonable distribution of weight in college performance measurement, this study extracts relevant indicators and quantitative data from the survey report of administrational institutions, and constructs a comprehensive performance measurement model based on the integration of fuzzy Delphi method (FDM), Entropy weight method (EWM), and grey relational analysis (GRA). The study seeks to identify differences in measurement analysis by comparing the weights, the performance and the rankings of the alternatives about higher vocational colleges in Zhejiang province. Finally, the results show the following: (1) by FDM, 33 indicators about colleges' performance are selected to form the evaluation system of the college's performance, (2) the indicators' weights are obtained through EWM and GRA, and a nonparametric test shows that there is no significant difference between the two types of weights, (3) the grey relational degrees of the alternatives are obtained and ranked on the basis of comprehensive evaluation model. By nonparametric test, there is a significant difference between the two types of relational degrees. On the contrary, no significant difference is found in the ranking of relational degrees, (4) based on the analysis results, this study further compares the performance of alternatives in different forms. There are significant differences between the performance of public colleges and private colleges, while no significant differences are observed between the performance of vocational colleges in Hangzhou and non-Hangzhou. Given the reliability and validity of the model, the comprehensive measurement model provides a relatively objective reference for college governance and administrational institutions, and also becomes an effective tool of colleges' evaluation to assist and improve the management practice in educational institutions.

Parametric Modeling and Optimization of Dimensional Error and Surface Roughness of Fused Deposition Modeling Printed Polyethylene Terephthalate Glycol Parts

Polyethylene Terephthalate Glycol (PETG) is a fused deposition modeling (FDM)-compatible material gaining popularity due to its high strength and durability, lower shrinkage with less warping, better recyclability and safer and easier printing. FDM, however, suffers from the drawbacks of limited dimensional accuracy and a poor surface finish. This study describes a first effort to identify printing settings that will overcome these limitations for PETG printing. It aims to understand the influence of print speed, layer thickness, extrusion temperature and raster width on the dimensional errors and surface finish of FDM-printed PETG parts and perform multi-objective parametric optimization to identify optimal settings for high-quality printing. The experiments were performed as per the central composite rotatable design and statistical models were developed using response surface methodology (RSM), whose adequacy was verified using the analysis of variance (ANOVA) technique. Adaptive neuro fuzzy inference system (ANFIS) models were also developed for response prediction, having a root mean square error of not more than 0.83. For the minimization of surface roughness and dimensional errors, multi-objective optimization using a hybrid RSM and NSGA-II algorithm suggested the following optimal input parameters: print speed = 50 mm/s, layer thickness = 0.1 mm, extrusion temperature = 230 °C and raster width = 0.6 mm. After experimental validation, the predictive performance of the ANFIS (mean percentage error of 9.33%) was found to be superior to that of RSM (mean percentage error of 12.31%).

3D Printing Technologies in Personalized Medicine, Nanomedicines, and Biopharmaceuticals

3D printing technologies enable medicine customization adapted to patients' needs. There are several 3D printing techniques available, but majority of dosage forms and medical devices are printed using nozzle-based extrusion, laser-writing systems, and powder binder jetting. 3D printing has been demonstrated for a broad range of applications in development and targeting solid, semi-solid, and locally applied or implanted medicines. 3D-printed solid dosage forms allow the combination of one or more drugs within the same solid dosage form to improve patient compliance, facilitate deglutition, tailor the release profile, or fabricate new medicines for which no dosage form is available. Sustained-release 3D-printed implants, stents, and medical devices have been used mainly for joint replacement therapies, medical prostheses, and cardiovascular applications. Locally applied medicines, such as wound dressing, microneedles, and medicated contact lenses, have also been manufactured using 3D printing techniques. The challenge is to select the 3D printing technique most suitable for each application and the type of pharmaceutical ink that should be developed that possesses the required physicochemical and biological performance. The integration of biopharmaceuticals and nanotechnology-based drugs along with 3D printing ("nanoprinting") brings printed personalized nanomedicines within the most innovative perspectives for the coming years. Continuous manufacturing through the use of 3D-printed microfluidic chips facilitates their translation into clinical practice.

FDM-based additive manufacturing of recycled thermoplastics and associated composites

Hailed since the fourth industrial revolution, three-dimensional (3D) printing or additive manufacturing (AM) has been extensively implemented in various manufacturing sectors. This process is popular for generating regular products and incorporating innovative designs into the components like auxetic structures, such as fabrication of engineering products, customized implants and sophisticated biomedical devices. Over the years, one of the interesting outputs of this emerging technology is the reuse of waste thermoplastic materials to produce competent products through the fused deposition modeling (FDM) technique. The strength of FDM components produced from thermoplastic waste is lower than that of virgin plastic FDM counterparts. So, there is a need to understand the significant changes in the recycled thermoplastic material during subsequent extrusions, which are chain scission, change in viscosity and breaking strength. The use of additives has been a promising solution to improve the performance of recycled material for 3D printing applications. Hence, this study aims to provide an overview of reusing plastic waste through FDM-based 3D printing. This review summarizes the current knowledge about the effect of processing on thermo-mechanical properties of recycled plastic FDM parts and the use of various additives to improve the overall quality. In addition, two case studies from open literature have been demonstrated to explain the use of FDM and associated technology for plastic recycling.