Prusa I3 Research Articles

Characterization of 3D Printed Polylactic Acid by Fused Granular Fabrication through Printing Accuracy, Porosity, Thermal and Mechanical Analyses.

Fused Granular Fabrication (FGF) or screw-extrusion based 3D printing for polymers is a less diffused alternative to filament-based Additive Manufacturing (AM). Its greatest advantage lies in superior sustainability; in fact, polymer granules can be used to directly feed an FGF printer, reducing the time, cost and energy of producing a part. Moreover, with this technology, a circular economy approach involving the use of pellets made from plastic waste can be easily implemented. Polylactic Acid (PLA) pellets were processed at different printing speeds and with different infill percentages on a customized version of a commercial Prusa i3 Plus 3D printer modified with a Mahor screw extruder. For the characterization of the 3D printed samples, rheological, thermal, mechanical and porosity analyses were carried out. In addition, the energy consumption of the 3D printer was monitored during the production of the specimens. The results showed that a higher printing speed leads to lower energy consumption, without compromising material strength, whereas a slower printing speed is preferable to increase material stiffness.

Mucoadhesive buccal films for treatment of xerostomia prepared by coupling HME and 3D printing technologies

Polyethylene oxide-based muco-adhesive buccal films containing adipic acid active pharmaceutical ingredient (API) and xylitol were developed using hot-melt extrusion (HME) coupled with Fused Deposition Modeling (FDM) three-dimensional (3D) printing. The immediate release mucoadhesive buccal films are intended for treatment or amelioration of xerostomia (dry mouth condition). Different formulae containing adipic acid and xylitol as the main saliva stimulating ingredients, and polyethylene oxide N80 (Polyox-N80) as the polymeric carrier were extruded using Thermo Scientific™ Process 11 Parallel Twin-Screw Extruder by Thermo Fisher Scientific (Waltham, MA, USA) equipped with 1.5 mm die. The extrudates were evaluated for printability using 3-point bend test and the ones which exhibited appropriate mechanical strength were 3D printed using Prusa i3 MK3 S 3D printer at 50 °C bed temperature, and 200 °C extruder temperature. The printed films demonstrated uniform content of adipic acid and desirable drug release upon quantification by high performance liquid chromatography. More than 80% of the adipic acid was released in 15 min and 100% of the adipic acid was released within 30 min. The DSC thermographs of the printed formulations revealed the adipic acid was dispersed in the polymer. The results of this study present an alternative formulation approach for the treatment of xerostomia by combining HME with FDM-3D printing for the development of muco-adhesive films containing adipic acid and xylitol.

Formulation development of loratadine immediate- release tablets using hot-melt extrusion and 3D printing technology

The main goal of this study was to develop immediate release Fused Deposition Modeling (FDM) 3D printed loratadine tablets using hot-melt extrusion (HME) filaments. Loratadine was used as a model drug with 10% (w/w) drug loading. Ten different formulations were prepared using Crospovidone and croscarmellose as super-disintegrants, mannitol as a pore-forming agent, and polyethylene oxide-N80 and hydroxypropyl cellulose-EF as polymeric carriers. A three-point bend test was performed to determine the filaments' elasticity, strength, and stiffness in order to evaluate the filaments printability. The printable filaments were then printed using an (Prusa i3 MK3S) FDM-3D printer in a grid pattern and with (40–60%) infill to accelerate the drug release. The physical mixtures, filaments, and 3D printed tablets were analyzed using differential scanning calorimetry (DSC). Fourier transform infrared spectroscopy (FTIR) was performed to investigate the interactions between loratadine and polymeric carriers. The in-vitro drug release profile of the printed tablets was tested. Based on the filament's mechanical properties, six filaments were printable. The DSC thermograms indicated complete solubilization of loratadine in the polymeric carrier. All printed tablets exhibited a drug release of (86.1–96.9%) in 30 min. HME showed great potential to develop immediate release filaments which were suitable for FDM-3D printing.

High-performance polymer 3D printing – Open-source liquid cooled scalable printer design

To print high-performance polymers, a stable running printer that can reach high temperatures is needed. There is currently a lack of low-cost solutions that allow manipulation of process parameters and expansion of sensors to monitor the printer as well as the process. This paper presents an open-source hardware upgrade for low-cost 3D printers to enable research on new high-temperature polymers as well as manufacturing from all currently available polymers. The hardware cost less than $1700, including the printer. Open-source firmware by Klipper and Fluidd is used for control. The printer is able to reach 500 °C nozzle, 200 °C heated bed, and 135 °C heated chamber with all electronics inside operating within the recommended temperature range. The presented design produced a CF-PEEK 3DBenchy and a spiral vase with excellent surface quality and no signs of delamination. Test specimens according to ISO527 using PA-CF performed similarly to the datasheet provided by the manufacturer for samples produced in the XY-orientation and outperformed the datasheet by 15 % in the ZX direction. Compared to specimens made on an Original Prusa i3 MK3S, the modified printer produced specimens with 22% higher strength in the YX-direction and 25% in ZX. By continuously monitoring and carefully calibrating both hardware and firmware, the presented design can perform as a research tool in material science and produce large-scale components of high-performance polymers.

Factors affecting ultimate tensile strength and impact toughness of 3D printed parts using fractional factorial design

This paper aims to investigate the mechanical properties of specimens printed by 3D open-source printers. It discusses the effect of five factors (part orientation, layer height, extrusion width, nozzle diameter, and filament temperature) on the ultimate tensile strength and the impact toughness of the 3D-printed samples. A 25–1 resolution V fractional factorial experiment was run with the 16 samples printed on a Prusa I3 MK3S in PLA. Tensile strength and impact toughness were tested using Instron 3367 and Tinius Olsen 66 testers, respectively. In analyzing the data, a normal probability plot of the effects complimented with ANOVA (Analysis Of Variance) revealed that, for both responses, only part orientation was statistically significant at p = 0.05. Regression equations were used to predict the ultimate tensile strength and the impact toughness as a function of the part orientation. Both the toughness response and the tensile strength response are maximized with horizontal part orientation. Verification experiments have been implemented to validate the adopted regression equations’ predictions under different circumstances, and the results of those experiments appear to confirm the model.

FABRICATION CYCLES COMPARISON OF ASSEMBLIES AND MONOLITHIC PARTS MADE BY 3D PRINTING METHOD

The article presents an analysis of the time-consuming, energy-consuming, and cost-consuming nature of 3D printing a three-dimensional polymer components made in two separate approaches: assembly and monolith structure of various materials (automatic filament change required). The introduction includes the definition of 3D printing, its advantages and examples of practical applications, as well as the reason for undertaking the researches described in the article. The justification of the form of 3D sample models was discussed in detail, as well as the methodology adopted by the authors for comparing the print characteristics and the steps of the printing cycles (print preparation, the course of the printing process and post-processing). A comparison of the materials consumption in the phasess of manual and automatic filament change in the mixer were also described. The test printout was made on the Prusa i3 MK3S printer for filament deposition (FDM or FFF methods). For automatic filament mixing, the Palette 2 Pro device was used. The conclusions also include guidelines for the design and production of models made in one continuous printing cycle (using automatic filament feeding devices). Monolithic elements are less accurate, while elements with replaceable filaments are cheaper, less energy-consuming and the material consumption is lower.

Additive Manufacturing of Polyaniline Electrodes

Since its discovery, polyaniline (PANI) has been a promising material for numerous applications due to its various desirable properties, e.g. tuneable conductivity, high pseudocapacitance or biocompatibility [1]. PANI has been incorporated as a composite for many electrochemical applications, from supercapacitors [2] to sensors [3], but its full potential is still limited by its poor processability as it cannot fully access the benefits of novel fabrication techniques like additive manufacturing (AM). The structural complexity and design flexibility of AM combined with the great properties of PANI would open up new application fields, from energy storage over wearable electronics to conductive implants. However, the non-thermoformable character of PANI limits the use of conventional AM techniques, e.g. Fused Deposition Modelling (FDM), to composites with only low PANI contents [4].Recently developed AM techniques using thermal doping of PANI [5] open up new possibilities for the use of PANI in AM. In this work, a novel process based on the thermal doping of PANI with dodecyl benzene sulfonic acid (DBSA) was used for the printing of electrodes for energy applications. For this, a commercially available FDM printer (Prusa i3 MK3S+) was modified with a 3D printed syringe extrusion system, replacing the regular print head. PANI emeraldine salt was synthesised using chemical oxidation and ultrasound at low temperatures, de-doped and ground to a small particle size. The polymer was then mixed with DBSA in order to obtain a viscous, printable paste. In this process, DBSA acts as both the dispersant and dopant for PANI. Thermal pre-treatment of the paste and the use of the printer hot-bed initiates the doping process, solidifying the paste, which allows for the AM of three dimensional conductive structures. The printing process was characterised and optimised in regards to pre-treatment time and temperature, hot bed temperature as well as nozzle distance from the hot bed. A fully 3D printed capacitor with PANI-DBSA electrodes and a polyvinyl alcohol/sulphuric acid electrolyte gel was fabricated and characterised in order to showcase the potential of this technique for electrochemical applications.[1] Baker, C. O., Huang, X., Nelson, W., Kaner, R. B., Chem Soc Rev 46 2581 (2001).[2]Shen, Y., Qin, Z., Li, T., Zeng, F., Chen, Y., Liu, N., Electrochimica Acta 356 136841 (2020).[3] Bao, Q., Yang, Z., Song, Y., Fan, M., Pan, P., Liu, J., Liao, Z., Wei, J., J. Mater. Sci.: Mater. Electron. 30 1751 (2018).[4] Wibowo, A., Vyas, C., Cooper, G., Qulub, F., Suratman, R., Mahyuddin, A. I., Dirgantara, T., Bartolo, P., Materials 13 512 (2020).[5] Holness, F., Price, A. D., Smart Mater. Struct. 1 015006 (2018).

Open-source hybrid 3D-bioprinter for simultaneous printing of thermoplastics and hydrogels

3D-bioprinting is a promising technology applicable in areas such as regenerative medicine or in vitro organ model development. Various 3D-bioprinting technologies and systems have been developed and are partly commercially available. Here, we present the construction and characterization of an open-source low-cost 3D-bioprinter that allows the alternated microextrusion of hydrogel and fused deposition modeling (FDM) of thermoplastic filaments.The presented 3D-bioprinter is based on a conventional Prusa i3 MK3 printer and features two independent printheads: the original FDM-head and a syringe-based microextrusion printhead for soft materials. Modifications were designed modularly to fit various syringe formats or heating elements to the device. The bioprinter is the first hybrid DIY 3D-bioprinter that allows switching between materials as often as required during a print run to produce complex multi-material constructs with arbitrary patterns in each layer.For validation of the printer, two designs suitable for relevant bioprinting applications were realized. First, a porous plastic construct filled with hydrogel was printed, serving as a mechanically stable bone replacement tissue model. Second, a plastic chamber, which might be used in organ-on-a-chip applications, was printed with an extruded silicone sealing that enables the liquid-tight attachment of glass slides to the top and bottom of the chamber.

Anisotropic Material Behaviors of Three-Dimensional Printed Carbon-Fiber Polymer Composites With Open-Source Printers

Abstract Composite products are often created using traditional manufacturing methods such as compression or injection molding. Recently, additive manufacturing (three-dimensional (3D) printing) techniques have been used for fabricating composites. 3D printing is the process of producing three-dimensional parts through the successful combination of various layers of material. This layering effect in combination with exposure to ambient (or reduced) temperature and pressure causes the finished products to have inconsistent microstructures. The inconsistent microstructures along with the oriented reinforcing fibers create anisotropic parts with difficulty to predict mechanical properties. In this paper, the mechanical properties of fiber-reinforced polymer composites produced by additive manufacturing technique (3D printing) and by traditional manufacturing technique (compression molding) were investigated. Three open-source 3D printers, i.e., FlashForge Dreamer, Tevo Tornado, and Prusa i3 Mk3, were used to fabricate bending samples from carbon-fiber-reinforced acrylonitrile butadiene styrene (ABS). Results showed that there exist significant discrepancies and anisotropies in mechanical properties of 3D-printed composites. First, the properties vary greatly among parts made from different printers. Second, the mechanical responses of 3D-printed parts strongly depend upon the orientations of the filaments. Parts with the infill oriented along the length of the specimens showed the most favorable mechanical responses such as Young’s modulus, maximum strength, and toughness. Third, all 3D-printed parts exhibit inferior properties to those made by conventional manufacturing. Finally, theoretical modeling has been attempted to predict the mechanical responses of 3D-printed products and can potentially be used to “design” the 3D printing processes to achieve the optimal performance.

Effect of heat treatment on the tensile properties of incrementally processed modified polylactide

The article presents the results of strength tests in the form of a static tensile test on the INSTRON 5967 testing machine. Samples were made with the use of the Prusa i3 MK3 3D printer, by modeling with a plasticized material (FFF) made of ABS copolymer, polylactide and its modified variant. According to the information provided by the manufacturer, heat-treated modified polylactide has mechanical properties similar to ABS copolymer filament. The publication also discusses the method of manufacturing elements subjected to the tests, the heat treatment process, as well as changes in material properties as a result of this treatment. Based on the test results, it was found that the annealing process increased the proportion of the crystalline phase, which significantly improved the strength properties of the modified polylactide.

QS2: DIY Bioreactors for Tissue Engineering - An Ultra-low-cost Platform for Perfusion Cell Culture and Live Imaging

Purpose:While tissue engineering offers the promise of revolutionary innovation, scalable three-dimensional tissue culture is limited by the diffusion of nutrients and oxygen making media perfusion obligatory. Unfortunately, the cost of bioreactors for large construct tissue culture can be prohibitive, with a typical perfusion chamber costing several thousand dollars, and even small petri-dish-sized devices costing hundreds of dollars each. We have developed a low-cost perfusion setup that seals collagen-based perfusable cellular constructs within a sterile PDMS well between coverslips, allowing for repeated live-imaging of perfused 3D engineered tissues. Herein we describe fabrication of this novel system and validate its utility.Methods:Molds and frames were designed on 3D-modeling software (Fusion 360) and printed on a Prusa i3 MK3S 3D printer in poly(lactic acid) (PLA). Molds were filled with poly(dimethyl siloxane) (PDMS), which was cured to form chambers, bubble traps, mason jar lid chambers, and media reservoir lid adapters. In total, the tissue culture chamber device, mason jar lid inset, media reservoir lid, and bubble trap require 4, 1, 2, and 4 unique printed components, respectively.Results:Each perfusion chamber can be assembled for under 8 USD per device and reused repeatedly. The current model has a tissue chamber custom-built with 18x10x4 (LxWxH)mm3 dimensions, but this chamber can be readily customized to experiment-specific dimensions. These devices allow cellular hydrogel constructs to be maintained in a sterile environment after assembly, perfused at varying rates to expose cells to different levels of shear stress, and the cells can be intermittently imaged with light, fluorescent or confocal microscopy - an unparalleled benefit for monitoring of experiments and collection of timepoint imaging data. The perfusion circuit consists of autoclavable glass and PDMS components, including a bubble trap, a crucial component of the circuit for preventing air bubbles that can damage cells and block microchannels, and a lid adapter, which allows 50 mL conical tubes to serve as self-oxygenating media reservoirs. Media changes can be performed via peristaltic pump perfusion or with syringe-based cell culture techniques for static culture. Constructs have been perfused within standard incubators for up to 14 days demonstrating normal cell viability without contamination or evidence of infection, with longer perfusion culture intervals (>1 month) currently being tested.Conclusion:The increasing accessibility of 3D-modeling and 3D-printing has enabled rapid prototyping of devices to address the problems that we face as surgeon-scientists. We have developed a low-cost tissue-engineering perfusion circuit that facilitates 3D-tissue-culture while allowing for repeated live-imaging as the cultured tissue develops. The instructions for our setup can be utilized to replicate our devices in other labs, and these designs can be readily customized to meet the needs of specific experimental aims.

15564 Going with the Flow: Engineering Vascularized Urothelial Flaps for Female-to-Male Phalloplasty in Transgender Patients

ABSTRACT IMPACT: This project uses rapid prototyping, 3D printing, and cell seeding to solve the most common post-operative complications that arise from the current methods of urethral elongation during phalloplasty. OBJECTIVES/GOALS: Post-op fistula and stricture formation occur in up to 50% of phalloplasty patients. These complications arise from the mismatch between skin and uroepithelium, or from scarring secondary to ischemia. Here we describe the fabrication of a novel vascularized urothelial flap for phalloplasty that contains discrete urothelial and vascular channels. METHODS/STUDY POPULATION: A custom designed 3D negative mold, with a urethral channel and a vascular inlet and outlet channel was prototyped in Adobe Fusion 360 and printed on a Prusa i3 MK3S printer in PLA. A 2mm diameter pluronic sacrificial macrofiber was used to connect the channels to form a vascular loop, and 1% type-I collagen was extruded over the mold. After solidifying, the scaffold was demolded and seeded with grade I urothelial carcinoma (SW780 cells, at 5-10 x 106 cells/mL) in the urethral channel, and adenovirus-infected E4 endothelial cells (at 3x106 cells/mL) in the vascular channel. The scaffolds were cultured up to 14 days and then fixed for histologic analysis. RESULTS/ANTICIPATED RESULTS: Collagen scaffolds were fabricated reliably using the custom 3D negative molds. After both seven and fourteen days of culture, the urothelial channel contained a robust, stable urothelial monolayer lining throughout the channel. By 14 days urothelial multilayer formation was seen, providing definitive evidence of a more mature urothelial layer. Grooves within the collagen allowed for nests of urothelial cells to develop, leading to increased multilayer formation. In addition, the vascular channels supported a healthy endothelial lining at both seven and fourteen days. There were no significant histological differences between constructs seeded with 5x106 urothelial cells/mL and 107 cells/mL. We anticipate that multilayer formation will increase with time, and that constructs will survive beyond 28 days. DISCUSSION/SIGNIFICANCE OF FINDINGS: We have developed a novel strategy to engineer vascularized urethral tissue. These constructs can be kept for at least 14 days and form stable monolayers and multilayers consistent with native urothelial architecture. Using 3D printing and autologous cell seeding promises to create patient-specific vascularized urethral flaps for phalloplasty.

Design and implementation of a low cost bio-printer modification, allowing for switching between plastic and gel extrusion

Due to the high cost of bioprinters they are not feasible for proof of concept experiments or educational purposes. Furthermore, the more affordable DIY methods all disable the plastic printing capability of the original printer. Here we present an affordable bio-printing modification that is easy to install and maintains the original capabilities of the printer. The modification used mostly 3D printed parts and is based on the popular, open-source Prusa i3 3D printer. The modifications are kept as simple as possible and uses standard slicing software, allowing for installation by less experienced builders. By using disposable syringes and easily sterilizable parts, an aseptic bioprinting setup can be achieved, depending on the environment. It also allows for 2 component printing as well as UV curing. The bio-printing and curing capabilities were shown by printing and curing an artificial biofilm of an electro-active bacteria, Geobacter sulfurreducens, onto a carbon-cloth electrode which was used in a microbial fuel cell.

Syringe pump extruder and curing system for 3D printing of photopolymers

Development of new additive manufacturing materials often requires the production of several batches of relatively large volumes in order to print and test objects. This can be difficult for many materials that are expensive or difficult to produce in large volumes on the laboratory scale. Bioprinter systems are advantageous in this regard, however, commercial systems are expensive or do not have the ability to use photopolymers. Herein, we outline a Syringe Pump Extruder and Curing System (SPECS) modification for inexpensive filament-based 3D printers which enables the use of standard bioplotter materials and photopolymers. The system is capable of using multiple syringe volumes and needle sizes that can be quickly and easily exchanged. The SPECS modification is demonstrated using a Prusa i3 mk3 fused filament fabrication printer to print several 3D objects and films using stereolithography (SLA) photopolymer resin. Geometric accuracy in the X, Y, and Z directions was ±0.1 mm using a 5 ml syringe, 22-gauge needle, and commercial SLA resin. The SPECS system could be of great benefit for laboratories pursing material development in the area of additive manufacturing.

Characterization of Ultrafine Particles and VOCs Emitted from a 3D Printer.

Currently, widely available three-dimensional (3D) printers are very popular with the public. Previous research has shown that these printers can emit ultrafine particles (UFPs) and volatile organic compounds (VOCs). Several studies have examined the emissivity of filaments from 3D printing, except glycol modified polyethylene terephthalate (PETG) and styrene free co-polyester (NGEN) filaments. The aim of this study was to evaluate UFP and VOC emissions when printing using a commonly available 3D printer (ORIGINAL PRUSA i3 MK2 printer) using PETG and NGEN. The concentrations of UFPs were determined via measurements of particle number concentration and size distribution. A thermal analysis was carried out to ascertain whether signs of fiber decomposition would occur at printing temperatures. The total amount of VOCs was determined using a photoionization detector, and qualitatively analyzed via gas chromatography-mass spectrometry. The total particle concentrations were 3.88 × 1010 particles for PETG and 6.01 × 109 particles for NGEN. VOCs at very low concentrations were detected in both filaments, namely ethylbenzene, toluene, and xylene. In addition, styrene was identified in PETG. On the basis of our results, we recommend conducting additional measurements, to more accurately quantify personal exposure to both UFPs and VOCs, focusing on longer exposure as it can be a source of potential cancer risk.

Accuracy Verification of an Anatomical Model Manufactured Using Low-Cost Additive Production

The paper deals with the separation of the third cervical vertebra using the software VGStudio MAX, Mimics, and inVesalius. During the separation, various parameters of the threshold were used to determine the effect. The comparison of models from Mimics and inVesalius to VGStudio MAX showed that the cumulative variance distribution for 95% surface coverage is less than 0.935 mm. When comparing medically oriented software, Mimics and inVesalius, the deviation was less than 0.356 mm. The model was made of polylactic acid (PLA) material on a low-cost 3D printer, Prusa i3 MK2.5 MMU1. The printed model was scanned by four scanners: Artec Eva, 3Shape D700, Steinbichler Comet L3D, and Creaform EXAscan. The outputs from the scanners were compared to the reference model (standard tessellation language (STL) model for 3D printing) as well as to the scanner with the best accuracy (3Shape). Compared to the publications below, the analysis of deviations was evaluated on the entire surface of the model and not on selected dimensions. The cumulative variance distribution for comparing the output from the 3D scanner with the reference model, as well as comparing the scanners, shows that the deviation for 95% of the surface coverage is at the level of 0.300 mm. Since the model of the vertebra is planned for education and training, the used software and technologies are suitable for use in the design and the production process.

Comparing cost and print time estimates for six commercially-available 3D printers obtained through slicing software for clinically relevant anatomical models

Background3D printed patient-specific anatomical models have been applied clinically to orthopaedic care for surgical planning and patient education. The estimated cost and print time per model for 3D printers have not yet been compared with clinically representative models across multiple printing technologies. This study investigates six commercially-available 3D printers: Prusa i3 MK3S, Formlabs Form 2, Formlabs Form 3, LulzBot TAZ 6, Stratasys F370, and Stratasys J750 Digital Anatomy.MethodsSeven representative orthopaedic standard tessellation models derived from CT scans were imported into the respective slicing software for each 3D printer. For each printer and corresponding print setting, the slicing software provides a print time and material use estimate. Material quantity was used to calculate estimated model cost. Print settings investigated were infill percentage, layer height, and model orientation on the print bed. The slicing software investigated are Cura LulzBot Edition 3.6.20, GrabCAD Print 1.43, PreForm 3.4.6, and PrusaSlicer 2.2.0.ResultsThe effect of changing infill between 15% and 20% on estimated print time and material use was negligible. Orientation of the model has considerable impact on time and cost with worst-case differences being as much as 39.30% added print time and 34.56% added costs. Averaged across all investigated settings, horizontal model orientation on the print bed minimizes estimated print time for all 3D printers, while vertical model orientation minimizes cost with the exception of Stratasys J750 Digital Anatomy, in which horizontal orientation also minimized cost. Decreasing layer height for all investigated printers increased estimated print time and decreased estimated cost with the exception of Stratasys F370, in which cost increased. The difference in material cost was two orders of magnitude between the least and most-expensive printers. The difference in build rate (cm3/min) was one order of magnitude between the fastest and slowest printers.ConclusionsAll investigated 3D printers in this study have the potential for clinical utility. Print time and print cost are dependent on orientation of anatomy and the printers and settings selected. Cost-effective clinical 3D printing of anatomic models should consider an appropriate printer for the complexity of the anatomy and the experience of the printer technicians.

Fibre misalignment and breakage in 3D printing of continuous carbon fibre reinforced thermoplastic composites

This paper investigates the formation of manufacturing induced fibre misalignment and breakage during fused filament fabrication (FFF) 3D printing of 1 K continuous carbon fibre filament. Single stripes at various turning angles and curvatures are printed by a desktop printer Prusa i3 using a specific brass nozzle and characterised using X-ray computed micro-tomography (µCT) and optical microscopy. A finite element (FE) model of the printing process is also established to support the experimental measurement. It has been found that high porosity and fibre misalignment in the printed straight stripe result from the weak fibre/matrix interface and the uneven pressure executed by the nozzle. Increase of turning angle and/or reducing of curvature radius leads to more aggravated printing defects, including shape inaccuracy, fibre twisting, folding and misalignment, due to the excessive force from the nozzle, debonding with the print bed and the unmatched geometry of nozzle outlet and fibre filament. Severe fibre breakage and significant change of thickness can be seen in the samples with turning angles larger than 120° or curvature radius smaller than 5 mm, while the wrinkles of the stripe in the inner periphery appear more frequently as the curvature radius decreases.

The Transferability and Design of Commercial Printer Settings in PLA/PBAT Fused Filament Fabrication.

In many fused filament fabrication (FFF) processes, commercial printers are used, but rarely are printer settings transferred from one commercial printer to the other to give similar final tensile part performance. Here, we report such translation going from the Felix 3.0 to Prusa i3 MK3 printer by adjusting the flow rate and overlap of strands, utilizing an in-house developed blend of polylactic acid (PLA) and poly(butylene adipate-co-terephthalate) (PBAT). We perform a sensitivity analysis for the Prusa printer, covering variations in nozzle temperature, nozzle diameter, layer thickness, and printing speed (Tnozzle, dnozzle, LT, and vprint), aiming at minimizing anisotropy and improving interlayer bonding. Higher mass, larger width, and thickness are obtained with larger dnozzle, lower vprint, higher LT, and higher Tnozzle. A higher vprint results in less tensile strain at break, but it remains at a high strain value for samples printed with dnozzle equal to 0.5 mm. vprint has no significant effect on the tensile modulus and tensile and impact strength of the samples. If LT is fixed, an increased dnozzle is beneficial for the tensile strength, ductility, and impact strength of the printed sample due to better bonding from a wider raster structure, while an increased LT leads to deterioration of mechanical properties. If the ratio dnozzle/LT is greater than 2, a good tensile performance is obtained. An improved Tnozzle leads to a sufficient flow of material, contributing to the performance of the printed device. The considerations brought forward result in a deeper understanding of the FFF process and offer guidance about parameter selection. The optimal dnozzle/vprint/LT/Tnozzle combination is 0.5 mm/120 mm s−1/0.15 mm/230 °C.

Tire Pressure Monitoring System Using an Android Application

Driving a vehicle with inadequate tire pressure can generate more ground friction, causing an increase in fuel consumption and, therefore in CO2 emissions. Another consequence is uneven tread wear, affecting braking distance and vehicle control. This paper presents the implementation of a Tire-Pressure Monitoring System (TPMS), which is a system that alerts the driver of a vehicle about a tire pressure change. For this, four prototypes were designed to monitor and transmit the tire pressure and temperature of a vehicle. For the transmitter circuits design, ATmega328 microcontrollers, NRF24L01 transceiver modules, Honeywell NBP series pressure sensors and LM35 temperature sensors were used. In addition, a receiver that incorporates an NRF24L01 module to receive the signals coming from the transmitters was developed. The received data are sent via Bluetooth, with the HC-05 module, to an Android application developed in App Inventor, which is an open-source web application. To install the circuits on the tires, compact cases were designed in Solidwork, which were printed using the Prusa i3 3D printer. The results obtained demonstrate the effectiveness of the monitoring system and the accuracy of the measured data, as well as the relevance of the Android application to alert the driver in a simple way about any pressure change in the tires. These results suggest the possibility of using the prototype developed in realistic scenarios to monitor tire pressure in vehicles without this technology.