For Fused Deposition Modeling Research Articles

Stress Simulation of the Structure of a Stretch Die Made by Fused Deposition Modeling

The paper is devoted to the assessment of the possibility to use a new design of a stretch die made of plastics used for fused deposition modeling (FDM) 3 D printing. Studies were conducted to assess the stress-strain state of a stretch die, from the normal pressure of a deforming sheet blank in a NASTRAN solver, using the finite element method. The convergence assessment of the simulation results was carried out for different quantities and corresponding sizes of finite elements. The optimal thicknesses of the hollow structure of the stretch die were determined by step-by-step calculations of its stress-strain state for acrylonitrile butadiene styrene (ABS) and polyethylene terephthalate glycol (PETG). On the basis of the conducted studies, a general algorithm was developed for the structural design of stretch dies made of plastics used for fused deposition modeling (FDM) printing.

Influence of the Halloysite Nanotube (HNT) Addition on Selected Mechanical and Biological Properties of Thermoplastic Polyurethane.

Halloysite nanotube (HNT) additions to the thermoplastic polyurethane (TPU) system were thoroughly evaluated in this study. The resultant composites have been designed for future personalized intervertebral disc implant applications, which requires additional technology to obtain the appropriate geometry unique to each patient. These requirements can be fulfilled using 3D printing. In this work, a technology was developed to produce filaments for fused deposition modeling (FDM). Nanocomposites were prepared using variable HNT content (1, 2, and 3 wt.%). The nanostructure of the resultant composites was confirmed using scanning transmission electron microscopy (STEM). Mechanical tests were used to measure the tensile modulus, stress, and elongation the composites and TPU matrix. Nanocomposites with 2% HNT content were able to withstand 26% increased stress and 50% increased elongation compared to pure TPU before fracturing in addition to a 13% reduction in the friction coefficient. A MTT cytotoxicity assay confirmed the cytotoxicity of all tested materials against human epidermal keratinocyte cells (HaCaT).

Optical characterization of 3D printed PLA and ABS filaments for diffuse optics applications.

The interest for Fused Deposition Modelling (FDM) in the field of Diffuse Optics (DO) is rapidly increasing. The most widespread FDM materials are polylactic acid (PLA) and acrylonitrile butadiene styrene (ABS), thanks to their low cost and easiness-to-print. This is why, in this study, 3D printed samples of PLA and ABS materials were optically characterized in the range from the UV up to the IR wavelengths, in order to test their possible employment for probe construction in DO applications. To this purpose, measurements with Near Infrared Spectroscopy and Diffuse Correlation Spectroscopy techniques were considered. The results obtained show how the material employed for probe construction can negatively affect the quality of DO measurements.

Stress-constrained topology optimization for material extrusion polymer additive manufacturing

Abstract This paper presents a comprehensive numerical and experimental study on stress-constrained topology optimization for Fused Deposition Modeling (FDM) additive manufacturing. The qp method is employed to avoid the singularity issue of stress-constrained problems. The P-norm function with stability transformation is adopted to build the global stress constraint with iterative corrections to eliminate the gap between the maximum local stress and the P-norm stress. The Heaviside projection is employed to generate clear-cut 0–1 designs. Two benchmark examples have been studied with the numerical algorithm. Experiments are performed on the topologically optimized MBB beam to investigate the impact of the FDM process parameters, including deposition path direction, building direction, and slicing layer height, on the resulted structural strength. The stress-constrained designs without and with Heaviside projection are comparatively tested with experiments. The stress-minimization designs subject to different P-norm parameters are compared both numerically and experimentally. Experiments show that the deposition path direction and the building direction evidently affect the derived structural strength. Moreover, overthin structural members may severely degrade the structural strength due to manufacturing and loading uncertainties.

Effects of Rice Straw Powder (RSP) Size and Pretreatment on Properties of FDM 3D-Printed RSP/Poly(lactic acid) Biocomposites

To develop a new kind of environment-friendly composite filament for fused deposition modeling (FDM) 3D printing, rice straw powder (RSP)/poly(lactic acid) (PLA) biocomposites were FDM-3D-printed, and the effects of the particle size and pretreatment of RSP on the properties of RSP/PLA biocomposites were investigated. The results indicated that the 120-mesh RSP/PLA biocomposites (named 120#RSP/PLA) showed better performance than RSP/PLA biocomposites prepared with other RSP sizes. Infrared results showed that pretreatment of RSP by different methods was successful, and scanning electron microscopy indicated that composites prepared after pretreatment exhibited good interfacial compatibility due to a preferable binding force between fiber and matrix. When RSP was synergistically pretreated by alkaline and ultrasound, the composite exhibited a high tensile strength, tensile modulus, flexural strength, and flexural modulus of 58.59, 568.68, 90.32, and 3218.12 MPa, respectively, reflecting an increase of 31.19%, 16.48%, 18.75%, and 25.27%, respectively, compared with unmodified 120#RSP/PLA. Pretreatment of RSP also improved the thermal stability and hydrophobic properties, while reducing the water absorption of 120#RSP/PLA. This work is believed to provide highlights of the development of cost-effective biocomposite filaments and improvement of the properties of FDM parts.

Optimization of Manufacturing Parameters and Tensile Specimen Geometry for Fused Deposition Modeling (FDM) 3D-Printed PETG.

Additive manufacturing provides high design flexibility, but its use is restricted by limited mechanical properties compared to conventional production methods. As technology is still emerging, several approaches exist in the literature for quantifying and improving mechanical properties. In this study, we investigate characterizing materials’ response of additive manufactured structures, specifically by fused deposition modeling (FDM). A comparative analysis is achieved for four different tensile test specimens for polymers based on ASTM D3039 and ISO 527-2 standards. Comparison of specimen geometries is studied with the aid of computations based on the Finite Element Method (FEM). Uniaxial tensile tests are carried out, after a careful examination of different slicing approaches for 3D printing. We emphasize the effects of the chosen slicer parameters on the position of failures in the specimens and propose a simple formalism for measuring effective mechanical properties of 3D-printed structures.

Highly toughened blends of poly(lactic acid) (PLA) and natural rubber (NR) for FDM-based 3D printing applications: The effect of composition and infill pattern

In this study, the suitability of natural rubber (NR) toughened poly(lactic acid) (PLA)-based blends were investigated for additive manufacturing applications. Filaments for fused deposition modeling (FDM) were prepared with an NR concentration of 0 … 20 wt% using a twin-screw extruder. Subsequently, specimens were fabricated with a desktop 3D printer machine working on FDM principles. Besides the composition of PLA/NR blends, the effect of infill orientation was also analyzed by preparing two sets of specimens: i) one set prepared with an alternating raster angle of ±45° (3DGRID) and ii) another one with a linear infill parallel to the length of the specimens (3DPAR). Quasi-static and dynamic mechanical properties, morphology and thermal characteristics of the fabricated specimens were investigated. The tensile tests revealed that the presence of NR effectively enhances the ductility of PLA filaments, however, the achieved improvement was highly dependent on the applied infill pattern. Samples prepared using the 3DPAR infill exhibited an excellent deformability when paired with NR. On the other hand, the ones fabricated with the 3DGRID technique only showed a marginal improvement in elongation. Similarly, the Charpy impact tests indicated an outstanding impact resistance of NR-toughened 3DPAR specimens, while the 3DGRID types showed little to no improvement. Scanning electron microscopic analysis revealed a weaker interlayer adhesion in the specimens containing NR, which greatly contributed to the discrepancies observed between the mechanical properties of the samples prepared with different infill. The differential scanning calorimetry revealed an almost completely amorphous structure of 3D printed PLA due to the quite rapid cooling characteristic of the FDM technique, which was not affected by the embedded NR component.

Potential for Natural Fiber Reinforcement in PLA Polymer Filaments for Fused Deposition Modeling (FDM) Additive Manufacturing: A Review

In this review, the potential of natural fiber and kenaf fiber (KF) reinforced PLA composite filament for fused deposition modeling (FDM) 3D-printing technology is highlighted. Additive manufacturing is a material-processing method in which the addition of materials layer by layer creates a three-dimensional object. Unfortunately, it still cannot compete with conventional manufacturing processes, and instead serves as an economically effective tool for small-batch or high-variety product production. Being preformed of composite filaments makes it easiest to print using an FDM 3D printer without or with minimum alteration to the hardware parts. On the other hand, natural fiber-reinforced polymer composite filaments have gained great attention in the market. However, uneven printing, clogging, and the inhomogeneous distribution of the fiber-matrix remain the main challenges. At the same time, kenaf fibers are one of the most popular reinforcements in polymer composites. Although they have a good record on strength reinforcement, with low cost and light weight, kenaf fiber reinforcement PLA filament is still seldom seen in previous studies. Therefore, this review serves to promote kenaf fiber in PLA composite filaments for FDM 3D printing. To promote the use of natural fiber-reinforced polymer composite in AM, eight challenges must be solved and carried out. Moreover, some concerns arise to achieve long-term sustainability and market acceptability of KF/PLA composite filaments.

Amphiphilic and segmented polyurethanes based on poly(ε-caprolactone)diol and poly(2-ethyl-2-oxazoline)diol: Synthesis, properties, and a preliminary performance study of the 3D printing

Polyurethanes (PU) have a wide variety of applications due to possessing tailored properties which can be imparted by composition. The combination of polyols in different ratios provide specific properties for the segmented PU, such as mechanical strength, elasticity, hydrophilicity and so on. In this work, amphiphilic and segmented polyurethanes, based on poly(ε-caprolactone)diol (PCL-diol) and poly(2-ethyl-2-oxazoline)diol (PEtOx-diol) at variable mass fractions, were synthesized by a two-step route and characterized according to composition, molar mass, thermal, dynamic mechanical, and rheological properties. Polyurethanes with molar masses ranging from 17.9 to 39.6 kDa, and a molar mass dispersity in the range of 2.0–4.0, are capable of swelling in water, with the swelling coefficient being modulated by the polyurethane composition and by the temperature because of the lower critical solubility temperature (LCST) behavior of PEtOx in an aqueous medium. PCL and PEtOx segments in the PU chains are partially miscible, therefore the polyurethanes are heterogeneous, presenting a PCL/PEtOx miscible phase dispersed in a PCL rich matrix in the solid state. PU with 50% mass fraction of PEtOx presented a gelation temperature of 69 °C, as determined by rheology, and was evaluated for Fused Deposition Modelling (FDM) 3D printing, showing promising features, although with a low resolution and fidelity to the computational project, mainly due to its high viscoelasticity which may be modulated by the molar mass of the polymer. Moreover, cell viability tests suggest that the polyurethanes are compatible with biomedical applications.

On recyclability of thermoplastic ABS polymer as fused filament for FDM technique of additive manufacturing

PurposeThe thermoplastic polymers do not decompose easily due to the presence of long-chain stable polymeric structure, and thus, causes serious effects on the environment. Recycling of these polymer wastes becomes the only solution to minimize their adverse effects on the environment. The purpose of this study was to explore the feasibility of using recycled thermoplastic material as filament for fused deposition modeling technique.Design/methodology/approachIn this study, the researchers fabricated fused filaments (in-house) for fused deposition modeling (FDM) technique of additive manufacturing from secondary recycled acrylonitrile butadiene styrene (ABS) by using a twin-screw extruder. After measuring the melt flow index of the secondary recycled ABS, the twin-screw extrusion parameters (rpm/speed of the screw, extrusion temperature and load) were varied to predict their influence on the various properties (rheological/mechanical/thermal) of the fabricated filaments. Experimental work was executed as per Taguchi’s L9 orthogonal array.FindingsThermal analysis performed to estimate the heat carrying capacity of recycled ABS highlighted that the heat capacity of ABS increases significantly from 0.28 J/g to 3.94 J/g during the heating cycle. The maximum value of peak strength and percentage break elongation for the fused filaments was investigated at 12.5 kg load, 2,250 C extrusion temperature and 70 rpm speed.Originality/valueThe filaments fabricated by recycling the polymeric waste has been successfully used in the FDM machine for the preparation of the three-dimensional printed tensile specimen.

Gain Enhancement of a Traditional Horn Antenna using 3D Printed Square-Shaped Multi-layer Dielectric Lens for X-band Applications

In this work, gain of a traditional horn antenna is enhanced up to 2.9 dB over X-band using 3D printed square-shaped multi-layer lens. For this purpose, firstly the multi-layer lenses are designed using Invasive Weed Optimization (IWO) and simulated in 3-D CST Microwave Studio (MWS) environment as consisting of square-shaped five layers with variable dielectric constants and heights. Thus, optimum values of the dielectric constants and heights are resulted limiting from 1.15 to 2.1 and 9.2 mm to 10 mm, respectively compatible for Fused Deposition Modeling (FDM) based 3D-printing process. Finally, the optimum lens is realized by 3D printer via FDM evaluating infill rate of cheap Polylactic Acid (PLA) material for each layer. The simulated and measured performance of the multi-layer dielectric structures are hand to hand. The horn antenna equipped by our proposed dielectric lens achieves gain enhancement of the traditional antenna up to 2.9 dB over the operation band. Furthermore, the proposed design is compared with the counterpart designs in literature and based on the comparison results it can be said that the proposed design achieves the better performance in the smaller in size as equipped a traditional X-band horn antenna.

Designing 3D printable polypropylene: Material and process optimisation through rheology

A polypropylene-based material has been formulated to be suitable for fused deposition modelling (FDM). In fact, the high volumetric shrinkage and the rheological behaviour are main problems whereby polypropylene (PP) is not commonly used as a 3D printing filament. Experimental results have evidenced how material modifications have a strong impact on rheological behaviour, providing critical features that permit and improve material printability. An optimised 20 wt% talc filled heterophasic PP copolymer has been developed. The peculiar properties of the materials have been assessed by thermal characterisation and rheological analysis. Several process parameters (extrusion temperature, screw speed, cooling conditions) have been evaluated in order to obtain a proper filament. Finally, a model part has been printed using different settings to check printing quality by morphological analysis.

Homogeneous distribution of lignin/graphene fillers with enhanced interlayer adhesion for 3D printing filament

AbstractThe attention to pursuing biodegradable fillers as reinforcement in three‐dimensional (3D) printing filament and enhancing interlayer adhesion has led to the exploitation of agricultural biomass. In this study, organosolv lignin fillers can act as the aforementioned twofold purposes in preparing acrylonitrile butadiene styrene (ABS) filament for fused deposition modeling (FDM). In this study, the lignin polymer composites were homogenized with graphene nanoplatelets (GnPs) as a reinforcer. Essentially, ABS 3D printing at 90o with the reinforcement fillers shows a significant increment in the mechanical properties owing to better interlayer adhesion. The printed product promotes a substantial improvement on the tensile stress up to 29.1% compared with neat polymers. Furthermore, 3D printing using lignin/GnP composite filaments shows the feasibility of biofillers to be used as filaments for FDM 3D printing of complex geometries even though the surface finish has been affected.

Carbon Nanotube-Based Composite Filaments for 3D Printing of Structural and Conductive Elements

In this publication, we describe the process of fabrication and the analysis of the properties of nanocomposite filaments based on carbon nanotubes and acrylonitrile butadiene styrene (ABS) polymer for fused deposition modeling (FDM) additive manufacturing. Polymer granulate was mixed and extruded with a filling fraction of 0.99, 1.96, 4.76, 9.09 wt.% of CNTs (carbon nanotubes) to fabricate composite filaments with a diameter of 1.75 mm. Detailed mechanical and electrical investigations of printed test samples were performed. The results demonstrate that CNT content has a significant influence on mechanical properties and electrical conductivity of printed samples. Printed samples obtained from high CNT content composites exhibited an improvement in the tensile strength by 12.6%. Measurements of nanocomposites’ electrical properties exhibited non-linear relation between the supply voltage and measured sample resistivity. This effect can be attributed to the semiconductor nature of the CNT functional phase and the occurrence of a tunnelling effect in percolation network. Detailed I–V characteristics related to the amount of CNTs in the composite and the supply voltage influence are also presented. At a constant voltage value, the average resistivity of the printed elements is 2.5 Ωm for 4.76 wt.% CNT and 0.15 Ωm for 9.09 wt.% CNT, respectively. These results demonstrate that ABS/CNT composites are a promising functional material for FDM additive fabrication of structural elements, but also structural electronics and sensors.

Exploring the possibilities of FDM filaments comprising natural fiber-reinforced biocomposites for additive manufacturing

<abstract> In recent years, with the recent advancements in the field of additive manufacturing, the use of biobased thermoplastic polymers and their natural fiber-reinforced biocomposite filaments have been rapidly emerging. Compared to their oil-based counterparts, they provide several advantages with their low carbon footprints, ease of reusability and recyclability and abundancy, and comparable price ranges. In consideration of their increasing usage, the present study focused on the development and analysis of biocomposite material blends and filaments by merging state-of-the-art manufacturing and material technologies. A thorough suitability study for fused deposition modeling (FDM), which is used to manufacture samples by depositing the melt layer-by-layer, was carried out. The mechanical, thermal, and microstructural characterization of birch fiber reinforced PLA composite granules, in-house extruded filaments, and printed specimens were investigated. The results demonstrated the printability of biocomposite filaments. However, it was also concluded that the parameters still need to be optimized for generic and flawless filament extrusion and printing processes. Thus, minimal labor and end-products with better strength and resolutions can be achieved. </abstract>

On rheological, mechanical, thermal, wear and morphological properties of melamine formaldehyde reinforced recycled ABS for sustainable manufacturing

This study outline the procedure of filament fabrication for fused deposition modelling (FDM), based upon rheological, mechanical, thermal, wear and morphological characterization as a case study of acrylonitrile butadiene styrene (ABS) - melamine formaldehyde (MF) composite. It has been ascertained that with increase in proportion of MF in ABS, viscosity is improved and melt flow index (MFI) is reduced significantly. As regards to the wear behavior is concerned it has been observed that ABS-MF (12.5 wt.%) composite has shown minimum weight loss and porosity. For the mechanical properties of the composite, experimental results show increased brittleness of the samples with addition of MF reinforcement. The thermal stability analysis was performed using differential scanning calorimetry (DSC) for virgin ABS and samples having 12.5% MF in ABS and results show the increased heat capacity of the material with increase in MF percentage. Further for sustainability analysis (based upon thermal stability), matrix of ABS-MF12.5% was subjected to three repeated thermal (heating-cooling) cycles and it has been ascertained that no significant loss was noticed in heat capacity of recycled composite matrix. The results are also supported by Fourier transform infrared spectroscopy (FTIR) analysis. Overall the results of the rheological, mechanical, wear, morphological and thermal properties suggested that 12.5% proportion of MF can be reinforced into selected grade of ABS thermoplastic for 3D printing as a sustainable solution.

A Feasibility Study of a Robotic Approach for the Gluing Process in the Footwear Industry

Manufacturing processes in the shoe industry are still characterized to a large extent by human labour, especially in small and medium craft enterprises. Even when machinery is adopted to support manufacturing operations, in most cases an operator has to supervise or carry out the task. On the other hand, craft footwear industries are called to respond to continuous challenges to face the globalization effects, so that a rapid adaptability to customer needs is required. The industry 4.0 paradigms, which are taking place in the industrial environments, represent an excellent opportunity to improve the efficiency and quality of production, and a way to face international competitors. This paper analyses and proposes a robotic cell to automatize the process of glue deposition on shoe upper, which exploits a new means of depositing the glue compared to State-of-Art applications. While the latter mainly adopt glue gun spraying systems or pneumatic syringes, the proposed robotic cell is based on an extrusion system for the deposition of molten material originally in the form of a filament, similar to all extent to those adopted for Fused Deposition Modeling (FDM). Two cell solutions are designed and tested. In the former the extruder is the robot end effector and the shoe upper is grounded to the cell frame. In the second, being the reciprocal, the shoe last is clamped to the robot wrist and the extruder is fixed to the cell frame. The peculiarities of the two solutions are pointed out and compared in terms of cell layout, hardware, programming software and possibility to develop collaborative applications. A self developed slicing software allows designing the trajectories for glue deposition based on the CAD model of the shoe upper, also allowing driving the inclination of the extruder nozzle with respect to the vectors normal to the upper surface. Both the proposed cell layouts permit to achieve good quality and production times. The solution with the mobile extruder is able to deposit glue at highest end-effector speed (up to 200 mm/s). On the other hand, the solution with the mobile shoe upper and fixed extruder seems to be more appropriate to enhance collaborative applications.

FDM 3D Printed Composites for Bone Tissue Engineering Based on Plasticized Poly(3-hydroxybutyrate)/poly(d,l-lactide) Blends.

Tissue engineering is a current trend in the regenerative medicine putting pressure on scientists to develop highly functional materials and methods for scaffolds’ preparation. In this paper, the calibrated filaments for Fused Deposition Modeling (FDM) based on plasticized poly(3-hydroxybutyrate)/poly(d,l-lactide) 70/30 blend modified with tricalcium phosphate bioceramics were prepared. Two different plasticizers, Citroflex (n-Butyryl tri-n-hexyl citrate) and Syncroflex (oligomeric adipate ester), both used in the amount of 12 wt%, were compared. The printing parameters for these materials were optimized and the printability was evaluated by recently published warping test. The samples were studied with respect to their thermal and mechanical properties, followed by biological in vitro tests including proliferation, viability, and osteogenic differentiation of human mesenchymal stem cells. According to the results from differential scanning calorimetry and tensile measurements, the Citroflex-based plasticizer showed very good softening effect at the expense of worse printability and unsatisfactory performance during biological testing. On the other hand, the samples with Syncroflex demonstrated lower warping tendency compared to commercial polylactide filament with the warping coefficient one third lower. Moreover, the Syncroflex-based samples exhibited the non-cytotoxicity and promising biocompatibility.

(Invited) Fabrication of Polymer Gels with Double Network Using Multi-Material 2/3D Printing

Multi-material systems for additive manufacturing, also known as 3D printing, are used to fabricate the functional objects with different color materials or with the position dependent material properties such as elastic modulus or solubility. The previous work for Fused Deposition Modeling (FDM) method have demonstrated that the multiple print heads or a single head with the mixed-material systems can extrude the complex and composite materials with piling up the multi-material layers connected with the physical bonds between layers.However, few studies have focused on the fabrication of 3D printed gel materials with different materials, and the creation of chemical bonds on the interface between the multi-material layers.In our previous work, 3D printed hollow objects made of gel materials were fabricated with a customized optical 3D printing system, and the 3D printed objects of multifunctional ionic gels incorporating ionic liquid (IL) in the thiol–ene network of thiol-based end-crosslinker and acrylate monomers were fabricated using commercial stereolithography (SLA) system. It was found that optical 3D printing system utilized to fabricate gel materials could create the microscale objects.This study report the design and fabrication of 3D printed polymer gels containing two types of gels using 3D gel printer named “SWIMER”. The double network technique for hydrogels is used for the creation of chemical bonds between two types of gels. Figure shows one of examples of 3D printed gel.This gel consists of two parts: the soft body frame for structural support which is made of nonionic polymer gels and the part which is made of the ionic polymer gels. The nonionic gels with an ordered structure are synthesized by the polymerization of the monomer, N,N-Dimethylacrylamide (DMAAm), and the crosslinker, N, N'-Methylenebisacrylamide (MBAA). The ionic gels are synthesized by the polymerization of the monomer, N-(1,1-Dimethyl-2-(sodiosulfo)ethyl)acrylamide and the same chemicals as the nonionic gels. Chemicals as the ultraviolet (UV) initiator are depending on the wavelength of laser source in the process of how we fabricate the gels.The significant difference in the swelling behavior between the two parts enabled them to be actuated in one direction. We found that by controlling the ion concentration in water they enlarged the solvent-induced strains to 108% in water which is comparable to the polymer actuators driven with high voltage. Figure 1

Polyetherimide powders as material alternatives for selective laser-sintering components for aerospace applications

Abstract