Filament Extrusion Research Articles

Process optimisation on the compressive strength property for the 3D printing of PLA/almond shell composite

In the fused deposition modelling technique, various type of thermoplastic is printed layer by layer. Among those biopolymers, Poly Lactic Acid occupies a massive space due to their excellent biodegradability. The present work concentrates on using almond shell particles as potential reinforcement in making Poly Lactic Acid (PLA) filaments by a filament extrusion process using a double screw extruder. The extruded filaments of 1.75 ± 0.5 mm diameter is used to make PLA/almond shell composite. This study distillates the effective process parameters for the 3D printing of PLA/almond shell composite and its compressive strength were evaluated. Design of Experiments is followed for the optimization process. The experiment was conducted by varying the five factors (infill pattern, infill density, printing orientation, printing temperature, and printing speed) and three levels. L27 orthogonal array is developed for the experimental procedure, and Taguchi optimization technique is employed for the optimization process for obtaining maximum compressive strength for the produced PLA/almond shell composite. The experimental results show that the infill density and printing orientation have a higher impact than the other printing process parameters with respect to the compressive properties. The mathematical models are developed from the optimization results for the compressive strength analysis of the PLA/almond shell composites. Based on the regression analysis results, the proposed mathematical model has an error percentage of 3.70% and has a good fit with the experimental results. Fractured samples clearly show that the higher infill density of PLA/almond shell samples doesn’t undergo premature buckling failure under the compressive loading.

INFLUENCE OF SLICER SOFTWARE USED WITH 3D PRINTING FILAMENT EXTRUSION TECHNOLOGY ON PROPERTIES OF PRINTED PARTS WITH SHORT FIBER REINFORCED THERMOPLASTIC COMPOSITE

3D printing with filament extrusion technology is a process in which the thermoplastic molten material is sequentially accumulated layer by layer on a construction platform. 3D printers use a slicer software that converts 3D digital models into printing instructions. The software calculates the trajectory of the extruder within the printer, from three-dimensional mesh-based models. The input of the lamination software is a “.stl” file and the output is a “.gcode” file. For each layer, the lamination program generates the path that the printer extruder will travel, this could determine if a part is correctly made or not. The objective of this study has been to analyze, with a view to industry implementation of the 3D printing, if the slicer software used in the extrusion 3D printing of short glass fiber reinforced thermoplastic, influences the final results that are obtained in the printed parts. It has been worked with four 3D printing slicer software, and it has been analyzed if there are significantly differences in mechanical and dimensional properties in the printed parts. For which, in the printing tests, always the same filament printer, printing material, part design, ".stl" file, and values for the percentage and type of filling, height layer and skin thickness have been used. The additive material used was a 2.85 mm diameter filament of 30% short glass fiber reinforced polyamide 6. It has been concluded that the slicer software, considering the evaluated ones, influences the results of the percentage of deformation at maximum tension, of the printed parts. The influence on the values of the resistance and the tensile modulus is not significant. Keywords: Filament fused fabrication (FFF), fused deposition modeling (FDM), short fibre composites, slicer software, printing parameters, tensile strength.

Experimental Analysis of Plastic-Based Composites Made by Composite Plastic Manufacturing

The significance of composites cannot be overstated in the manufacturing sector due to their unique properties and high strength-to-weight ratio. The use of thermoplastics for composites manufacturing is also gaining attention due to their availability, ease of operation, and affordability. However, the current methods for plastic-based composites are limited due to the requirements of long curing times and pre- and post-treatment, thereby resulting in longer lead times for the desired product. These methods also limit the freedom to operate with different forms of materials. Therefore, a new manufacturing process for plastic-based composites is required to overcome such limitations. This research presents a new manufacturing process to produce high-quality plastic-based composites with bespoke properties for engineering applications. The process is referred to as Composite Plastic Manufacturing (CPM) and is based on the principle of fused filament fabrication (FFF) equipped with a heat chamber. The process integrates two material extrusion additive manufacturing technologies, i.e., filament and syringe extrusion. The paper presents the principle of the process, both in theory and in practice, along with the methodology and materials used to manufacture plastic composites. Various composites have been manufactured using the CPM process with thermally activated materials and tested according to British and International standards. Polylactic Acid (PLA) has been interlaced with different thermally activated materials such as graphene-carbon hybrid paste, heat cure epoxy paste, and graphene epoxy paste. The process is validated through a comparative experimental analysis involving tests such as ultrasonic, tensile, microstructural, and hardness to demonstrate its capabilities. The results have been compared with commercially available materials (PLA and Graphene-enhanced PLA) as well as literature to establish the superiority of the CPM process. The CPM composites showed an increase of up to 10.4% in their tensile strength (54 MPa) and 8% in their hardness values (81 HD) when compared to commercially available PLA material. The composites manufactured by CPM have also shown strong bonding between the layers of PLA and thermally activated materials; thus, highlighting the effectiveness of the process. Furthermore, the composites showed a significant increase of up to 29.8% in their tensile strength and 24.6% in their hardness values when compared to commercially available Graphene-enhanced PLA material. The results show that the CPM process is capable of manufacturing superior quality plastic composites and can be used to produce products with bespoke properties.

Volatile organic compound and particulate emissions from the production and use of thermoplastic biocomposite 3D printing filaments

Biocomposites (BCs) can be used as substitutes for unsustainable polymers in 3D printing, but their safety demands additional investigation as biological fillers may produce altered emissions during thermal processing. Commercial filament extruders can be used to produce custom feedstocks, but they are another source of airborne contaminants and demand further research. These knowledge gaps are targeted in this study. Volatile organic compound (VOC), carbonyl compound, ultrafine particle (UFP), and fine (PM2.5) and coarse (PM10) particle air concentrations were measured in this study as a filament extruder and a 3D printer were operated under an office environment using one PLA and four PLA-based BC feedstocks. Estimates of emission rates (ERs) for total VOCs (TVOC) and UFPs were also calculated. VOCs were analyzed with a GC-MS system, carbonyls were analyzed with an LC-MS/MS system, whereas real-time particle concentrations were monitored with continuously operating instruments. VOC concentrations were low throughout the experiment; TVOC ranged between 34–63 µg/m3 during filament extrusion and 41–56 µg/m3 during 3D printing, which represent calculated TVOC ERs of 2.6‒3.6 × 102 and 2.9‒3.6 × 102 µg/min. Corresponding cumulative carbonyls ranged between 60–91 and 190–253 µg/m3. Lactide and miscellaneous acids and alcohols were the dominant VOCs, while acetone, 2-butanone, and formaldehyde were the dominant carbonyls. Terpenes contributed for ca. 20–40% of TVOC during BC processing. The average UFP levels produced by the filament extruder were 0.85 × 102–1.05 × 103 #/cm3, while the 3D printer generated 6.05 × 102–2.09 × 103 #/cm3 particle levels. Corresponding particle ERs were 5.3 × 108–6.6 × 109 and 3.8 × 109–1.3 × 1010 #/min. PM2.5 and PM10 particles were produced in the following average quantities; PM2.5 levels ranged between 0.2–2.2 µg/m3, while PM10 levels were between 5–20 µg/m3 for all materials. The main difference between the pure PLA and BC feedstock emissions was terpenes, present during all BC extrusion processes. BCs are similar emission sources as pure plastics based on our findings, and a filament extruder produces contaminants at comparable or slightly lower levels in comparison to 3D printers.

Types of 3D Printers Applied in Industrial Pharmacy and Drug Delivery

The promising technology depend on using 3D printers' machines (3DPs) might be considered a modern approach in drug industry and delivery. A 3D printer may define as a machine which fabricates 3D models or products using computer aided design (CAD) software programs. These printers can create a single copy of an item that is too complicated and very difficult to produce by using traditional manufacturing methods. Moreover, it has ability to make products with complex internal structure geometries with lower cost and time. Recently, 3D printers have been involved into printing bio-products, custom pills and organs for transplant. This review presents the types of 3DPs suitable for drug industry and delivery. There are several types of 3DPs are used in pharmaceutical fields including inkjet (IK) printers, fused filament (FF) type printers, extrusion and hot melt extrusion 3D printing, sintering by selective kind of laser (SLS), Stereolithography (SLA), melting by micro selective laser (SLM), binder applied jetting printing (BJ) and the laminated object engineering manufacturing (LOM).

Antibacterial activity of ciprofloxacin-impregnated 3D-printed polylactic acid discs: an in vitro study.

Three-dimensional (3D) printing technology allows incorporation of various substances including antibiotics into different structures. This study aimed to evaluate the antibacterial activity of ciprofloxacin-impregnated 3D discs against Escherichia coli. Polylactic acid pellets were coated with ciprofloxacin at 1% and 2% concentrations, then filaments were produced from these pellets, and antibiotic-containing discs were obtained using fused deposition modeling 3D printers. The working temperatures during filament extrusion and 3D printing processes were 200 °C and 215 °C, respectively. Therefore, in order to test the thermal stability of ciprofloxacin during these processes, the antibiotic was exposed to 200 °C and 215 °C in an oven, and then tested against E. coli. Following this, efficiencies of antibiotic-coated pellets, filaments and discs against E. coli were determined by diffusion tests. Ciprofloxacin heated at 200 °C and 215 °C was stable and retained its antibacterial activity. Pellets, filaments and discs coated with 1% or 2% concentration of ciprofloxacin produced inhibition zones in the culture plates. Increasing ciprofloxacin concentration did not significantly affect the diameter of inhibition zones (p > 0.05). Ciprofloxacin-containing polylactic acid pellets produced significantly larger inhibition zones than those of filaments and discs (p < 0.0001). The difference in zone diameters around ciprofloxacin-containing filaments and discs was not statistically significant (p > 0.05). Ciprofloxacin-coated polylactic acid-based 3D discs displayed antibacterial activity against E. coli. This suggests that, various polylactic acid-based ciprofloxacin-containing 3D products can be obtained and evaluated for antibacterial activity in future studies.

A review about polylactic acid filament recycling to 3D printing process / Uma revisão sobre a reciclagem de filamentos de ácido poliláctico ao processo de impressão 3D

Additive manufacturing, specifically 3D printing (3DP), is a trend of great relevance in industry 4.0. The objective of this work is presented as a systematic review of the available literature to define the main methods and standards towards analyzing the material properties, 3D printing filament extrusion variables, and polylactic acid (PLA) recycling. The research used the methodology of a mixed explanatory sequential review based on studies already published in books and journals. These data have relevant information to serve as a guide for the recycling, extrusion, and 3D printing of the PLA.

3D printing of composite materials using ultralow-melt-viscosity polymer and continuous carbon fiber

We propose a composite 3D printing method using an ultralow-melt-viscosity polymer to achieve a low void content and high strength compared to that achieved using conventional viscosity polymer. Using continuous carbon fibers as the core of the filament, ultralow-viscosity polymers, which could not be filamentized by polymer alone, could be used. In the present study, polyether ether ketone/carbon fiber (CF/PEEK) filament extrusion was performed and the effect of the melt viscosity on the voids in the filament was evaluated. The ultralow-viscosity polymer (CF/PEEK 90 G) reduced the voids in the filaments by 92% compared to the standard polymer (CF/PEEK 450 G). The interlaminar tensile strengths of 3D-printed CF/PEEK filaments fabricated with different melt viscosities of the PEEK polymer were also evaluated. The interlaminar tensile strengths of CF/PEEK 90 G was improved by 116.8% compared to that of CF/PEEK 450 G.

Valuable effect of Manuka Honey in increasing the printability and chondrogenic potential of a naturally derived bioink.

Hydrogel-based bioinks are the main formulations used for Articular Cartilage (AC) regeneration due to their similarity to chondral tissue in terms of morphological and mechanical properties. However, the main challenge is to design and formulate bioinks able to allow reproducible additive manufacturing and fulfil the biological needs for the required tissue. In our work, we investigated an innovative Manuka honey (MH)-loaded photocurable gellan gum methacrylated (GGMA) bioink, encapsulating mesenchymal stem cells differentiated in chondrocytes (MSCs-C), to generate 3D bioprinted construct for AC studies. We demonstrated the beneficial effect of MH incorporation on the bioink printability, leading to the obtainment of a more homogenous filament extrusion and therefore a better printing resolution. Also, GGMA-MH formulation showed higher viscoelastic properties, presenting complex modulus G∗ values of ∼1042 ​Pa, compared to ∼730 ​Pa of GGMA. Finally, MH-enriched bioink induced a higher expression of chondrogenic markers col2a1 (14-fold), sox9 (3-fold) and acan (4-fold) and AC ECM main element production (proteoglycans and collagen).

Reprocessability of PLA through Chain Extension for Fused Filament Fabrication

As additive manufacturing (AM) technologies have been gaining popularity in the plastic processing sector, it has become a major concern to establish closed-loop recycling strategies to maximize the value of the materials processed, therefore enhancing their sustainability. However, there are challenges to overcome related to the performance of recycled materials since, after mechanical recycling, the molecular degradation of thermoplastics shifts their performance and processability. In this work, it was hypothesized that the incorporation of a chain extender (CE) during the reprocessing would allow us to overcome these drawbacks. To attest this conjecture, the influence of 1,3-Bis(4,5-dihydro-2-oxazolyl)benzene (PBO), used as a CE, on mechanical, thermal, and rheological properties of polilactic acid (PLA) was studied. Furthermore, a closed-loop recycling system based on Fused Filament Fabrication (FFF) was attempted, consisting of the material preparation, filament extrusion, production of 3D components, and mechanical recycling steps. PBO partially recovered the recycled PLA mechanical performance, reflected by an increase in both tensile modulus (+13%) and tensile strength (+121%), when compared with recycled PLA without PBO. Printability tests were conducted, with the material’s brittle behavior being the major constraint for successfully establishing a closed-loop recycling scheme for FFF applications.

Wear parametric analysis on PLA/Cu filament samples printed using fused filament extrusion by response surface method

Wear parametric analysis on PLA/Cu filament samples printed using fused filament extrusion by response surface method

Poly(L-co-D,L lactic acid-co-Trimethylene Carbonate) 3D printed scaffold cultivated with mesenchymal stem cells directed to bone reconstruction: In vitro and in vivo studies.

A recent and quite promising technique for bone tissue engineering is the 3D printing, peculiarly regarding the production of high-quality scaffolds. The 3D printed scaffold strictly provides suitable characteristics for living cells, in order to induce treatment, reconstruction and substitution of injured tissue. The purpose of this work was to evaluate the behavior of the 3D scaffold based on Poly(L-co-D,L lactic acid-co-Trimethylene Carbonate) (PLDLA-TMC), which was designed in Solidworks™ software, projected in 3D Slicer™, 3D printed in filament extrusion, cultured with mesenchymal stem cells (MSCs) and tested in vitro and in vivo models. For in vitro study, the MSCs were seeded in a PLDLA-TMC 3D scaffold with 600μm pore size and submitted to proliferation and osteogenic differentiation. The in vivo assays implanted the PLDLA-TMC scaffolds with or without MSCs in the calvaria of Wistar rats submitted to 8mm cranial bone defect, in periods of 8-12weeks. The results showed that PLDLA-TMC 3D scaffolds favored adherence and cell growth, and suggests an osteoinductive activity, which means that the material itself augmented cellular differentiation. The implanted PLDLA-TMC containing MSCs, showed better results after 12weeks prior grafting, due the absence of inflammatory processes, enlarged regeneration of bone tissue and facilitated angiogenesis. Notwithstanding, the 3D PLDLA-TMC itself implanted enriched tissue repair; the addition of cells known to upregulate tissue healing reinforce the perspectives for the PLDLA-TMC applications in the field of bone tissue engineering in clinical trials.

Living with an enemy: Invasive sun-coral (Tubastraea spp.) competing against sponges Desmapsamma anchorata in southeastern Brazil

The azooxanthellate corals Tubastraea coccinea and T. tagusensis invaded the Brazilian coast in the 1980s and is still in expansion, favored by lower predation and competition pressure in their new habitats. Interestingly, the native sponge Desmapsamma anchorata has been observed overgrowing these corals. Considering that competitive displacement is expected to play a major role in the successful outcome of an invasion, the present study tested the physical and chemical mechanisms possibly involved in the competition between D. anchorata and the Tubastraea corals through field and aquaria experiments as well as the Raman spectroscopy technique for chemical analysis. Our results showed that the sponge grew in all directions including over Tubastraea colonies and regardless of its presence. There was no evidence of a specific chemical response among sponges or corals. However, we observed the extrusion of mesenteric filaments and tentacles of corals and the projection of sponge tissue during interspecific interaction, which suggests that physical imposition plays a key role for space competition at micro scales. Given the interspersed nature of benthic species distributions and the fast expansion of Tubastraea, it is unlikely that D. anchorata or any other sponges could serve a biological control against these invasive corals at larger scales, but our results showed that at a microscale they can withstand the corals presence and even outgrow them locally.

An investigation of the influence of 3d printing parameters on the tensile strength of PLA material

Fused Deposition Modelling (FDM), also known as 3d printing, is one of the most widespread Additive Manufacturing (AM) technologies based on the extrusion of a thermoplastic filament. This layerwise technology allows lightweight products to be built using different infill strategies and percentages. Furthermore, by varying other parameters, such as temperature, printing speed or layer thickness, it is possible to obtain components with different characteristics. Polylactic Acid (PLA) is one of the cheapest and most sustainable materials for 3d printing because it is a biobased and biodegradable plastic. Its use in 3D printing is widely spread among hobbyists and in the communities, such as the ones of Fablabs or the Makers movement.Nevertheless, to reduce the number of uncompliant parts that may fail into operation since they do not meet the expectations of the user, it is important to know in advance the mechanical performance that different 3d printing strategies can ensure for PLA parts.In this paper, Design of Experiment (DOE) is applied to investigate how main 3D printing parameters influence the tensile strength of PLA products. For this purpose, a 3x3 factorial plane with one replication was constructed and used for 3d printing tensile specimens of PLA Tough material using a Makerbot Replicator machine. The tensile test results show that the layer thickness is more significant than the infill percentage for the resistance of PLA products. A regression model is also proposed to allow the user to predict the ultimate tensile strength of PLA products depending on the values of those two parameters.

Development of a custom setup for additive manufacturing of high-performance thermoplastics

Fused Filament Fabrication (FFF) is an addictive manufacturing process based on the extrusion of a continuous filament of thermoplastic material. There are several materials that are suitable for this production process, including high-performance plastics such as Polyether Ether Ketone (PEEK) or Polyetherimide (PEI). These high-performance thermoplastics produce components with higher strength and toughness than the standard printing plastics, as well as optimized thermal properties.A machine was designed and developed to produce specimens in these high-performance thermoplastics for further study of their physical and mechanical performance. This machine was designed using the CubeX 3D printer produced by 3D Systems as a base, retaining the main essential structure and kinematics to which several modifications were made so that it can work under the extreme operating conditions required for printing these materials. The main changes made to the original machine were the control board, that was replaced by the Duet 2 Wi-Fi Board, the extruder, changed to the E3D Titan Aqua and the build plate which was replaced by with the E3D High Temperature Heated Bed. In addition, a custom glycol-based cooling setup was implemented to cool both the extruder and the machine’s stepper motors, along with the development of a custom heating system for the printing environment.The proposed system has been successfully constructed, being able to produce functional parts in both PEEK and PEI plastics. Further research on the mechanical properties of the specimens produced is in progress.

3D PRINTING OF BIO-INSPIRED CORES FOR OUT-OF-AUTOCLAVE SANDWICH STRUCTURES

The design and manufacture of sandwich structures allow for many variants related to core and skin types, but their fabrication is very limited with conventional technologies. Recent advances in 3D printing are creating new design possibilities, such as bio-inspired structures with more complex cellular units than the current ones, functional gradients, and curved panels. The present work has focused on two aspects; 1) the efficiency of the core inspired by the trabecular structure of beetle wings versus the conventional honeycomb, and 2) the feasibility of integrating these new cores with carbon fiber/epoxy prepreg skins for out-of-autoclave curing.&nbsp; The results show that the ONYX&reg; 3D printing cores obtained by filament extrusion technology and the skins manufactured by out-of-autoclave curing show good skin/core adhesion. On the other hand, the results of the flexural tests have shown that the stiffness of the sandwich panel with the trabecular structure is better than that of one of the honeycombs and the strength in both cases is similar. However, where substantial differences have been found between the two types of cores is in the quasi-static puncture resistance, that of the trabecular structure being 60% higher.

Realization of Multi–Property Design by Multi–Filament Extrusion

Realization of Multi–Property Design by Multi–Filament Extrusion

Mathematical Modelling of Temperature Distribution in Selected Parts of FFF Printer during 3D Printing Process.

This work presented an FEM (finite element method) mathematical model that describes the temperature distribution in different parts of a 3D printer based on additive manufacturing process using filament extrusion during its operation. Variation in properties also originate from inconsistent choices of process parameters employed by individual manufacturers. Therefore, a mathematical model that calculates temperature changes in the filament (and the resulting print) during an FFF (fused filament fabrication) process was deemed useful, as it can estimate otherwise immeasurable properties (such as the internal temperature of the filament during the printing). Two variants of the model (both static and dynamic) were presented in this work. They can provide the user with the material’s thermal history during the print. Such knowledge may be used in further analyses of the resulting prints. Thanks to the dynamic model, the cooling of the material on the printing bed can be traced for various printing speeds. Both variants simulate the printing of a PLA (Polylactic acid) filament with the nozzle temperature of 220 °C, bed temperature of 60 °C, and printing speed of 5, 10, and 15 m/s, respectively.

Rheological properties of powder blend for extrusion of ceramic-polymer filament used in 3D printing

The article presents the results of comparative studies of the rheological properties of the ceramic polymer blend of polylactide (PLA) filled with 50 %vol alumina to evaluate the possibility of obtaining extruded filament for 3D printing.

Temperature, diffusion, and stress modeling in filament extrusion additive manufacturing of polyetherimide: An examination of the influence of processing parameters and importance of modeling assumptions

Fused filament fabrication (FFF), a form of filament-based material extrusion additive manufacturing (AM), is an extremely useful technique for the rapid production of highly customized products; however, empirical evidence is heavily relied upon for understanding of the process. Initial modeling attempts have traditionally focused on predicting heat transfer and either interlayer diffusion and adhesion or stress development but have not taken a combined approach to analyze all three components simultaneously in a multiphysics model. In this study, we implement finite difference models to examine the combined heat transfer, polymer diffusion represented as degree of healing (Dh), and residual stress development in FFF of poly(ether imide) (PEI). Printing with PEI is of great interest because of its desirable mechanical properties and high use temperatures, but it also creates a more challenging modeling problem with higher thermal gradients and greater potential thermal processing window compared to traditionally modeled AM materials, such as acrylonitrile-butadiene-styrene (ABS) and polylactic acid (PLA). The larger processing window can potentially allow for more processing options but can also significantly complicate the optimization process. In this study, experimental analyses including trouser tear tests and part warpage measurements provide correlation to predicted Dh and stress levels. The models suggest that the temperature of a layer is influenced by the subsequent printing of up to at least three layers in the geometry studied. The results of this study further demonstrate the sensitivity of the molecular mobility and degree of healing to the reptation time (τrep), such that a small change in the τrep on the order of 2–3x can result in an order of magnitude difference in the time before interfacial healing can begin, culminating in significantly less healing occurring. Furthermore, the reptation time and subsequent healing predictions are highly reliant on the extrapolation method used to extend the reptation time to temperatures below those at which it was measured resulting in significantly different predictive results, even if the same experimental data is used.