Fused deposition modeling (FDM) is one of the widely used additive manufacturing technologies because it has flexibility and ability to build complex parts. The accuracy of parts fabricated by FDM is ...greatly influenced by various process parameters. FDM process has a complex mechanism in building parts and often poses difficulty in understanding adequately how conflicting FDM parameters will determine part quality and accuracy. Sectors such as medical implant, telecommunication, electronics and aerospace require increasingly higher levels of dimensional accuracy. Thus, traditional methods of ensuring quality do not effectively address global markets and customer’s needs. This study proposes an I-optimality criterion for the optimization of FDM process parameters in order to address the limitations of the commonly used traditional designs. This study also aims to develop mathematical models in order to establish nonlinear relationship between process parameters and dimensional accuracy. The results show that I-optimality criterion is very promising technique in FDM process parameter optimization. Confirmation experiments show that the proposed method has great advantages in the aspect of both accuracy and efficiency compared with traditional methods proposed in previous studies.
In this study, high-performance flexible strain sensors based on carbon nanotube (CNT) and graphene nanoplatelet (GNP) filled thermoplastic polyurethane (TPU) composites were fabricated via Fused ...Filament Fabrication (FFF) 3D printing. The introduction of GNPs generated a more complete conductive network of the composites due to the improved nanofiller dispersion. Due to the synergy of CNTs and GNPs, the printed CNT/GNP(3:1)/TPU sensor shows higher sensitivity (GF = 136327.4 at 250% strain), larger detectable range (0–250% strain), and better stability (3000 cycles) compared with the CNT/TPU and GNP/TPU sensors with a nanofiller content of 2 wt%. Furthermore, the printed sensors can accurately detect strains at different frequencies (0.01–1 Hz). A modelling study based on tunneling theory was conducted to analysis the strain sensing mechanism, and the theoretical results agreed well with the experimental data. The capability of the sensors in monitoring physiological activities and speech recognition has also been demonstrated.
Three-dimensional (3D) printing has been successfully applied for the fabrication of polymer components ranging from prototypes to final products. An issue, however, is that the resulting 3D printed ...parts exhibit inferior mechanical performance to parts fabricated using conventional polymer processing technologies, such as compression moulding. The addition of fibres and other materials into the polymer matrix to form a composite can yield a significant enhancement in the structural strength of printed polymer parts. This review focuses on the enhanced mechanical performance obtained through the printing of fibre-reinforced polymer composites, using the fused filament fabrication (FFF) 3D printing technique. The uses of both short and continuous fibre-reinforced polymer composites are reviewed. Finally, examples of some applications of FFF printed polymer composites using robotic processes are highlighted.
A method is presented to characterize the fracture resistance and interlayer adhesion of fused deposition modeling (FDM) 3D printed materials. Double cantilever beam (DCB) specimens of acrylonitrile ...butadiene styrene (ABS) were designed and printed with a precrack at the layers' interface. The DCBs were loaded in an opening mode and the load-displacement curves were synchronized with the optical visualization of the crack tip to detect the critical load at the crack initiation. A finite element model, coupled with J-integral method and fracture surface analysis was then developed to obtain the apparent fracture resistance (Jcr,a) and the interlayer fracture resistance (Jcr,i), as a measure of the interlayer adhesion. The maximum Jcr,i was measured to be 4017 J/m2, a value close to the fracture resistance of bulk ABS. Both Jcr,a and Jcr,i increased with the printing temperature. This method can find a great importance in the structural applications of printed materials.
Since the advent of 3D printing in the mid-1980s, additive manufacturing has grown steadily and found numerous applications across all types of industries. More recently, the industry has seen a spur ...of growth as the terms of the original patents expired and new companies entered the market. While there exist several different methods of additive manufacturing, polymer-based material extrusion 3D printing (also known as fused filament fabrication) has become one of the most widely used ones due to its lower cost, ease of use, and versatility. While development has greatly expanded the material availability and improved the quality of prints, material extrusion 3D printers have often faced a challenge in physical scaling. There are inherent design hurdles to the extrusion process when the print starts to grow larger. This paper aims to study the market landscape of extrusion-based 3D printing technology for polymer-based material as well as challenges faced in upscaling this technology for industrial applications. A prototype large-scale material extrusion 3D printer has been designed, constructed, and then tested to gain experimental data on large-scale 3D printing using thermoplastic polymers as a printing material. Results of testing and experimentation verified certain key design elements and how they can improve large-scale 3D printing. Testing also revealed how large diameter nozzles for the hot end introduce challenges not seen in small-scale 3D printers. This paper also seeks to consolidate available information pertaining to large-scale 3D printing into one comprehensive document.
The accuracy of three-dimensional (3D) printing is how the dimensions of a measured product are close to its original model's nominal values. Thus, dimensional accuracy is essential for determining ...the machine's reliability to produce each object according to the expected results. In this study, the influence of 3D printing process parameters on the dimensional accuracy of specimens manufactured using Polylactic acid (PLA) material is investigated. Based on fused deposition modeling (FDM) technology, cylindrical and dog-bone tensile test samples are fabricated at various process parameters, including build orientation, raster direction angle, and layer thickness. PLA filaments with three different colors (white, grey, and black) are utilized to produce the required test pieces. The dimensional accuracy for cylindrical (diameter and length) and dog-bone (width and thickness) samples have been evaluated. The nominal values are considered the reference to determine the accuracy percentage for each specimen. The weight of all test pieces is also examined, and its precision is assessed. The optimum process parameter settings have been defined to minimize the error percentage in the dimensions of the printed parts. According to the results, a high overall dimensional accuracy of 98.81% was achieved, which indicates the ability of commercial FDM 3D printers as an inexpensive and decent quality alternative for producing utilitarian parts. The filament's color displayed a notable impact on the test pieces' weight, where the difference between the heaviest (white) and lightest (black) specimens is almost a percentage of 7.24%. A remarkable influence was noticed for the layer thickness parameter on the accuracy, meanwhile the raster direction angle parameter appeared no effect when the number of layers and the contour size are the same. The data obtained from this study might help identify the optimum configurations that guide the production of components using thermoplastic filaments through FDM 3D printing.
The main purpose of this research is to bolster mechanical properties of the parts, produced by an extrusion-based 3D printer, or fused deposition modeling machine, via increasing the content of ...continuous fiber yarn to its practical limit. In-melt continuous glass fiber yarn embedding was applied as a reliable and consistent method for simultaneous impregnation to produce continuous fiber-reinforced thermoplastic composites in the fused deposition modeling process. It is well known that the main weakness in the fused deposition modeling 3D printed products is their low strength compared to the manufactured ones by conventional methods such as injection molding and machining processes. This characteristic can be related to both inherent weakness of thermoplastic materials and poor adhesion between the deposited rasters and the layers. Although various attempts have been performed to tackle this issue, it is widely believed that using continuous fibers is the most effective method to serve this purpose if a reliable and consistent method is implemented. Since the mechanical properties of continuous fiber-reinforced composites directly depend on the content of fiber volume, maximizing the fiber content as well as producing an integrated part was assumed as the main objective. In this work, an analysis of various patterns of raster deposition was conducted, followed by the experiments and verification. The effective parameters on the fiber yarn volume, such as fiber yarn diameter, fiber yarn laying pattern, extrusion width, layer height, and flow percentage, were investigated and their optimal values were reported. The attained experimental results showed that, for polylactic acid-glass fiber yarn reinforced composite, with the extrusion width of 0.3 mm, the layer heights of 0.22 mm, flow percentage of 0.43, and the rectangular laying pattern, approximately 50% fiber-volume content can be achieved which resulted in tensile yield strength and modulus of 478 MPa and 29.4 GPa, respectively. There was an excellent agreement between these experimental results and predicted theoretically values by rule of mixture.
Purpose
The purpose of this research is present an experimental and numerical study of the mechanical properties of the acrylonitrile butadiene styrene (ABS) in the additive manufacturing (AM) by ...fused filament fabrication (FFF). The characterization and mechanical models obtained are used to predict the elastic behavior of a prosthetic foot and the failure of a prosthetic knee manufactured with FFF.
Design/methodology/approach
Tension tests were carried out and the elastic modulus, yield stress and tensile strength were evaluated for different material directions. The material elastic constants were determined and the influence of infill density in the mechanical strength was evaluated. Yield surfaces and failure criteria were generated from the tests. Failures over prosthetic elements in tridimensional stresses were analyzed; the cases were evaluated via finite element method.
Findings
The experimental results show that the material is transversely isotropic. The elasticity modulus, yield stress and ultimate tensile strength vary linearly with the infill density. The stresses and the failure criteria were computed and compared with the experimental tests with good agreement.
Practical implications
This research can be applied to predict failures and improve reliability in FFF or fused deposition modeling (FDM) products for applications in high-performance industries such as aerospace, automotive and medical.
Social implications
This research aims to promote its widespread adoption in the industrial and medical sectors by increasing reliability in products manufactured with AM based on the failure criterion.
Originality/value
Most of the models studied apply to plane stress situations and standardized specimens of printed material. However, the models applied in this study can be used for functional parts and three-dimensional stress, with accuracy in the range of that obtained by other researchers. The researchers also proposed a method for the mechanical study of fragile materials fabricated by processes of FFF and FDM.
Industrial hemp hurd (HH) is emerging as a bio-based filler in thermoplastic biocomposites. In this paper, HH/polylactide (PLA) biocomposites were developed as fused deposition modelling (FDM) ...feedstock through parametric analysis of the effects of HH loading with respect to melt flow, rheology, physical, thermo-mechanical, and mechanical properties of the biocomposites. Poly (butylene adipate-co-terephthalate) (PBAT) and ethylene-methyl acrylate-glycidyl methacrylate terpolymer (EGMA) were used as toughening and compatibilisation agents respectively in melt-compounding and extrusion to produce FDM filament. The FDM-printed standard samples were compared against corresponding injection-moulded biocomposites. The FDM filament exhibited a diameter tolerance within ±0.02 mm, and roundness variability below 0.03 mm, and the FDM-printed parts with HH loading under 30 phr showed higher impact toughness than the commercial PLA filament control. In addition, the FDM-printed samples exhibited greater dimensional accuracy with increasing HH loading.
Three-dimensional (3D) printing continuous carbon fiber-reinforced polylactic acid (PLA) composites offer excellent tensile mechanical properties. The present study aimed to research the effect of ...process parameters on the tensile mechanical properties of 3D printing composite specimens through a series of mechanical experiments. The main printing parameters, including layer height, extrusion width, printing temperature, and printing speed are changed to manufacture specimens based on the modified fused filament fabrication 3D printer, and the tensile mechanical properties of 3D printing continuous carbon fiber-reinforced PLA composites are presented. By comparing the outcomes of experiments, the results show that relative fiber content has a significant impact on mechanical properties and the ratio of carbon fibers in composites is influenced by layer height and extrusion width. The tensile mechanical properties of continuous carbon fiber-reinforced composites gradually decrease with an increase of layer height and extrusion width. In addition, printing temperature and speed also affect the fiber matrix interface, i.e., tensile mechanical properties increase as the printing temperature rises, while the tensile mechanical properties decrease when the printing speed increases. Furthermore, the strengthening mechanism on the tensile mechanical properties is that external loads subjected to the components can be transferred to the carbon fibers through the fiber-matrix interface. Additionally, SEM images suggest that the main weakness of continuous carbon fiber-reinforced 3D printing composites exists in the fiber-matrix interface, and the main failure is the pull-out of the fiber caused by the interface destruction.
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