3D-printed Specimens Research Articles

Build Orientation Influence on some Mechanical Properties of 3D-Printed Polyamide Specimens

Additive manufacturing [AM] is a type of production technology characterized by the additive nature of stacking and unifying individual layers, with the main advantage that parts with complex geometries can easily be obtained, compared to conventional production methods. Due to its working principle, i.e. stacking layers, obtained by melting and solidification, the mechanical characteristics of the built part might be influenced by the build orientation chosen for the specific part. The mechanical behavior, cyclic deformation and fatigue behaviors of additively manufactured metallic parts as compared to their counterparts obtained by conventional processing technologies was reported to be highly dependent on the build orientation. The aim of this study was to assess whether the build orientation will have an impact on the mechanical properties of parts built by Selective Laser Sintering, using polyamide powder as raw material. Samples were built at various inclination degrees, and were further tested in terms of bending, compressive, impact and hardness tests. It was observed that the build orientation has a significant effect on the mechanical properties of parts additively manufactured from polyamide, compared to the behavior presented on the technical sheet of the material, provided by the manufacturer. Keywords: additive manufacturing, mechanical properties, build orientation, Selective Laser Sintering

Effect of selected printing settings on viscoelastic behaviour of 3D printed polymers with and without wood

The viscoelastic behaviour of 3D printed samples produced from different types and contents of commercially produced filaments of wood and thermoplastics at different printing settings was investigated in this study. An Ares G2 rheometer was used to carry out the dynamic mechanical analysis (DMA) of the printed materials. A strain sweep and a temperature ramp test were made to evaluate the effect of 3D printing settings, materials, and temperature on the properties of the 3D-printed specimens. Five different printing materials (ABS, PLA, co-polyesters, mixtures with different wood content) and three printing layer thicknesses (0.09, 0.19, 0.29 mm) were used. The result showed that the specimens printed from Filament C (polymer blend of co-polyesters) had the lowest storage modulus while the highest modulus was found in the PLA based samples. When comparing pure PLA and PLA-wood filaments, the addition of wood particles decreased the storage modulus by 40%. The glass transition temperature (Tg) of the materials differed with each other. The specimens printed from ABS had the highest Tg 115 °C, followed by the specimens printed from co-polyester-based filament (around 70 °C), pure PLA, and PLA-wood filaments (64 °C–66 °C). The addition of wood did not change the glass transition temperature, since the main matrix was made of polymer. The viscoelastic behaviour of the 3D printed neat polymer and wood/polymer parts produced at different processing parameters and conditions can be considered for filament producers for material selection and the design engineers when wood/PLA printed parts fabricated through FDM technique.

Structure and Mechanical Properties of 3D-Printed Ceramic Specimens

The paper presents the research results of the structure, phase composition and mechanical properties of aluminum oxide ceramic specimens obtained by the additive manufacturing technology. The manufacturing process and the original equipment are described. The formation of several types of pores and surface boundaries between the layers is shown during ceramic 3D printing. It is found that for the different printing strategies, the different mechanical properties are observed in the obtained specimens that are stipulated by the structural anisotropy.

Development of a zoomorphic test specimen for constancy testing on digital X-ray systems in veterinary radiology

BackgroundTechnical failures and incorrect usage of digital X-ray systems may lead to a decreasing image quality, artefacts and a higher dose exposure of staff and patients. Although there are no regulations regarding constancy testing in veterinary radiology all operators are required to avoid unnecessary exposure. The aim of this study was to develop a reasonably inexpensive zoomorphic 3D-printed test specimen for constancy testing that allows the detection of changing image quality by visual analysis.Primarily, a calibration curve of the attenuation factor of the 3D-printing material (ZP150) was determined. MATLAB converted every pixel value of a thorax X-ray image of a Beagle dog into an equivalent thickness of printing material. The thickness distribution was printed using a 3D-printer. This printed test specimen was additionally provided with five thin aluminium discs to simulate lung nodules.To evaluate the usability for constancy testing 12 X-ray images of the test specimen were made. Two images (reference and control) were taken with the minimum dose in order to obtain images suitable for diagnosis purposes. Eight images were taken with a dose differing 30–140% from the reference dose by varying current–time product (mAs) or tube voltage (kVp). Two images were taken with the same parameters as the reference image but edited with different image processing. Six veterinarians (general practitioners) evaluated ten chosen structures in the X-ray images in a Visual Grading Analysis and scored the image quality of these structures for every image in comparison to the reference image. A Visual Grading Analysis Score was calculated and statistically analysed.ResultsA higher current–time product led to a negligibly better evaluation of the X-ray image. The lower the current–time product the worse the X-ray images were scored. Likewise, both increasing and decreasing of the tube voltage led to lower scores.ConclusionsA zoomorphic test specimen can be used for constancy testing of digital X-ray systems in veterinary medicine. Especially a lower dose can be recognised due to deviation in the image quality when compared to the reference image. The 3D-printed test specimen is less expensive than test equipment used in human medicine.

Comparative assessment of anatomical details of thoracic limb bones of a horse to that of models produced via scanning and 3D printing

BackgroundThree-dimensional (3D) scanning and printing for the production of models is an innovative tool that can be used in veterinary anatomy practical classes. Ease of access to this teaching material can be an important aspect of learning the anatomy of domestic animals. In this study, a scanner was used to capture 3D images and a 3D printer that performs die-cast printing was used to produce skeletal models of the thoracic limb of a horse.MethodsBones from a horse were selected for scanning and creation of 3D-printed models. The printer used a filamentous thermoplastic material (acrylonitrile-butadiene-styrene [ABS]) which was deposited together with a support resin. Comparisons of the anatomical characteristics (measurements from the original and printed bone) were analyzed to determine the p-value.ResultsBones from the thoracic limb: scapula, humerus, radius and ulna, carpus and phalanges were used to produce digital and physical models for 3D impressions. Then the anatomical characteristics of the 3D printed models were compared with those of the original bones. The p-value was measured to be 0.9126, indicative of a strong evidence of similarity between the 3D-printed models and specimens. Thus, there was no significant statistical difference between the models and the original anatomical parts.ConclusionsThe anatomical characteristics were successfully identified in the 3D-printed copies, demonstrating that models of animal bones can be reproduced using 3D printing technology for use in veterinary education.

Classifying Degraded Three-Dimensionally Printed Polylactic Acid Specimens Using Artificial Neural Networks based on Fourier Transform Infrared Spectroscopy

Fused filament fabrication (FFF) is commonly employed in multiple domains to realize inexpensive and flexible material extrusion systems with thermoplastic materials. Among the several types of thermoplastic materials, polylactic acid (PLA), an environment-friendly bio-plastic, is commonly used for FFF for the sake of the safety of the manufacturing process. However, thermal degradation of three-dimensionally (3D)-printed PLA products is inevitable, and it is one of the failure mechanisms of thermoplastic products. The present study focuses on the thermal degradation of 3D-printed PLA specimens. A classification methodology using artificial neural networks (ANNs) based on Fourier transform infrared (FTIR) and was developed. Under the given experimental conditions, the ANN model could classify four levels of thermal degradation. Among the FTIR spectra recorded from 650 cm−1 to 4000 cm−1, the ANN model could suggest the best wavenumber ranges for classification.

Failure Observation of 3D-Printed Thrust Bearing Specimens with Inner Defects in Water Conditions

Additive manufacturing (AM) methods are developing and have become popular, but questions remain about the strength of parts made by this method. We have already investigated the effect of the lamination direction on the fractures in bearing specimens. In this study, we made inner defects in the 3D-printed bearing specimens and performed rolling contact fatigue (RCF) tests on this specimens immersed in a water bath in order to investigate the fracture of 3D printed bearings.

3D printing of carbon nanotubes reinforced thermoplastic polyimide composites with controllable mechanical and electrical performance

Existing aerospace metal parts or structural parts have the problems of finite elasticity, large mass, difficult manufacture of complex parts, expensive equipment, narrow range of shielding and electrostatic regulation. This study analyzed the tensile and bending properties of pure thermoplastic polyimide (TPI) 3D printing specimens printed by the nozzles with different diameters. The effects of different carbon nanotube (CNT) contents on the thermal and electrical properties of carbon nanotube composites were investigated. The relationship between the electrical conductivity, tensile properties, bending properties, resistivity and cyclic bending deformation of 3D printed specimens with different carbon nanotube contents was studied. Compared with the 0.4 mm nozzle, the tensile and bending strength of pure TPI specimen printed by a 0.8 mm nozzle were increased by 40% and 20%, respectively. In order to ensure the excellent mechanical and electrical properties of 3D printed composites, 3%wt carbon nanotubes-thermoplastic polyimide (CNTs-TPI) composites with appropriate tensile and bending strength were used to print the characteristic structure, and then the relationship between the deformation and conductive resistance was studied. By optimizing the 3D printing parameters and the filling contents of CNTs, it is possible to print complex parts which can be used in aerospace and industrial fields with special properties, such as electrical conductivity, mechanical properties, temperature resistance and anti-electromagnetic shielding.

Validation of an in-house-designed tensile testing machine for the mechanical characterization of 3D-printed specimens

Additive manufacturing is gaining greater and greater popularity in recent years: thanks to a dramatic reduction of costs and increasing print quality, more and more people are attracted to 3D printing, even for the production of end-use load-bearing parts. Today, there are no universally accepted norms that guide the engineer through the uncertain task of predicting the mechanical behavior of 3D-printed parts. Even though there are numerous reports and articles in literature regarding this topic, the designer will have to rely mostly on his own mechanical tests. This paper describes the design of an in-house-built machine for 3D-printed material tensile testing. The accuracy of this test-rig has been verified through comparison of results on different 3D-printed specimens: these were realized through fused deposition modelling (FDM) and were divided into four distinct sets, based on the material and their orientation on the buildplate. Some samples were printed in PLA, others in XTCF-20™: a composite material made of a matrix of Amphora™ polymer reinforced with 20% in weight carbon short fibers. PLA samples were printed flat on the buildplate, on one side and standing: this affects directly the orientation of the plastic fibers. Tensile tests were performed both on ours and on a high-end commercial testing machine, following the ISO 527 norm. Maximum stress, strain at maximum stress and Young’s modulus were calculated for each tested specimen: these measures allowed to compare the results of the two testers. Results proved coherent, thus validating the in-house machine, which was realized for a fraction of the cost of an equivalent commercial model.

Mechanical properties and water absorption behaviour of PLA and PLA/wood composites prepared by 3D printing and injection moulding

Purpose This papers aims to study the influence of water absorption on the mechanical properties of poly lactic acid (PLA) and PLA/Wood composites. Virgin PLA and PLA/Wood double-bone-shaped specimens were prepared by two methods: injection moulding and 3D printing. The results were compared to each other and showed the influence of the production method on the properties of the produced parts. Design/methodology/approach Morphology studies were done by scanning electron microscopy (SEM) from fracture surfaces of tensile and notched impact specimens of all samples. Tensile properties were analysed by the production and testing of dog-bone-shaped samples. Heat deflection temperature (HDT) was tested, as also was the crystallinity of the tested samples by differential scanning calorimetry. Findings The values for notched impact strength were higher upon water uptake in the case of injection-moulded specimens, which was not the case with 3D-printed specimens. Tensile properties of the specimens produced by both methods were reduced after water absorption tests. Values of the HDT were also lower after water absorption tests studied for both processing methods. Originality/value Morphology studies were done by SEM from fracture surfaces of tensile as well as notched impact specimens of injection-moulded and 3D-printed samples. The effect of water storage on various samples was tested. The two different production technologies were compared to each other owing to their influence of water storage. This study also dealt with NFC compounds and produced NFC composites and the influence of water storage on these samples.

Multiplane fused deposition modeling: a study of tensile strength

A conventional three dimensional (3D) printer utilizes horizontal planar layering to produce 3D printed parts. The development of a higher degree of freedom 3D printing platform allows for vertical and horizontal layering to be achieved in the same print. 3D-printed specimens were created using a conventional Cartesian 3D printer that utilizes layer upon layer deposition in a single plane. Multiplane 3D printed specimens were also created, using a robot arm platform with multiplane layering capabilities. All of the test specimens were put through tensile tests to characterize the mechanical properties of multiplane layered parts compared to single-plane layered parts. Three printing orientations, upright, on-edge, and horizontal, were used for both the conventional 3D printer and the robot arm platform 3D printer processes. The results show that the multiplane layering method implemented by the robot arm 3D printer improved the modulus of elasticity, the yield strength, and the ultimate tensile strength of the tensile specimens in the upright printing orientation compared to the specimens created by the conventional 3D printer. These results can be used to improve the design of 3D printed parts that require specific mechanical characteristics.

3D-printing of arsenic sulfide chalcogenide glasses

The use of a 3D-printing additive manufacturing process is reported for the first time for the extrusion of chalcogenide glasses by using a filament feed. Several challenges were overcome: preparation of chalcogenide glass filaments by the crucible technique, optimization of extrusion temperature or even filament feeding. The As40S60 chalcogenide glass was selected for its low glass transition temperature (Tg = 188°C) and ease of synthesis and processing. It was extruded using a commercial 3D-printer at a temperature around 140°C above the glass transition temperature. 3D-printed glass specimens were then characterized and no significant difference was observed in comparison with the bulk precursor glass in terms of chemical and thermal properties. This first report of additive manufacturing of chalcogenide glass complex shapes paves the way for the development of novel specialty optical components that could not be produced by conventional methods, including the fabrication of multimaterial optical fiber preforms.

Additive Manufacturing of Three-Phase Syntactic Foams Containing Glass Microballoons and Air Pores

High-density polyethylene and its syntactic foams reinforced with 20 vol.% and 40 vol.% glass microballoons were 3D printed using the fused filament fabrication method and studied for their compressive response. The three-phase microstructure of syntactic foams fabricated in this work also contained about 10 vol.% matrix porosity for obtaining light weight for buoyancy applications. Filaments for 3D printing were developed using a single screw filament extruder and printed on a commercial 3D printer using settings optimized in this work. Three-dimensional printed blanks were machined to obtain specimens that were tested at 10−4 s−1, 10−3 s−1, 10−2 s−1 and 1 s−1 strain rates. The compression results were compared with those of compression-molded (CM) specimens of the same materials. It was observed that the syntactic foam had a three-phase microstructure: matrix, microballoons and air voids. The air voids made the resulting foam lighter than the CM specimen. The moduli of the 3D-printed specimen were higher than those of the CM specimens at all strain rates. Yield strength was observed to be higher for CM samples than 3D-printed ones.

Effect of printing layer thickness on water absorption and mechanical properties of 3D-printed wood/PLA composite materials

Effect of printing layer thickness on technological properties of 3D-printed specimens fabricated from wood flour/PLA filaments having a diameter of 1.75 mm was investigated. For this aim, four different printing layers, 0.05 mm, 0.1 mm, 0.2 mm, and 0.3 mm, were used in the production of the 3D-printed specimens. The water absorption of the specimens (28 days immersion in water) increased with increasing printing layer thickness while the thickness swelling decreased. The tensile and bending properties of the specimens significantly improved with decreasing printing layer thickness. The increase in the layer thickness caused bigger gaps, which increased the porosity in the cross section of the specimen. Higher porosity resulted in lower mechanical properties.

Characterization of process–deformation/damage property relationship of fused deposition modeling (FDM) 3D-printed specimens

In this paper, we investigated the process variable effects on the damage and deformational behavior of fused deposition modeling (FDM) three-dimensional (3D)-printed specimens by performing tensile tests and inverse identification analyses. A characterization of the effects of different parametric variations of 3D-printed specimens on fracture properties are a matter of considerable significance that are often overlooked. By combining the infill density and the layer thickness options that are available in the 3D printer machine, six groups with different structural configurations can be obtained. The data and images obtained from experiments are employed to investigate the failure mechanism of 3D-printed specimens and demonstrate the relationship that exists between structural variations and fracture mechanical properties. On the basis of experimental results, a Gurson-type porous plasticity model was used within a 3D continuum finite element model to characterize the process–damage parameter relationship through an inverse identification process.

Imaging natural history museum collections from the bottom up: 3D print technology facilitates imaging of fluid-stored arthropods with flatbed scanners.

Availability of 3D-printed laboratory equipment holds promise to improve arthropod digitization efforts. A 3D-printed specimen scanning box was designed to image fluid-based arthropod collections using a consumer-grade flatbed scanner. The design was customized to accommodate double-width microscope slides and printed in both Polylactic Acid (PLA) and nylon (Polyamide). The workflow with two or three technicians imaged Trichoptera lots in batches of six scanning boxes. Individual images were cropped from batch imagess using an R script. PLA and nylon both performed similarly with no noticeable breakdown of the plastic; however, dyed nylon leeched color into the ethanol. The total time for handling, imaging, and cropping was ~8 minutes per vial, including returning material to vials and replacing ethanol. Image quality at 2400 dpi was the best and revealed several diagnostic structures valuable for partial identifications with higher utility if structures of the genitalia were captured; however, lower resolution scans may be adequate for natural history collection imaging. Image quality from this technique is similar to other natural history museum imaging techniques; yet, the scanning approach may have wider applications to morphometrics because of lack of distortion. The approach can also be applied to image vouchering for biomonitoring and other ecological studies.

Structure and mechanical properties of 3D-printed cellulose tablets by fused deposition modeling

This paper evaluated corn starch/cellulose acetate (SCA) specimens 3D-printed by the fused deposition modeling (FDM) method. The influence of the printing parameters, nozzle temperature, and flow rate on the morphological and mechanical properties of the specimens was evaluated. Scanning electron microscopy (SEM) showed smooth surfaces on all the 3D-printed specimens. The fracture surface analysis revealed homogeneity and low porosity of the specimens printed at 230 °C and 90% flow rate. The flexural tests showed high values of the flexural modulus for the specimens printed at 240 °C and 80% flow rate, and the fatigue tests demonstrated that the 230-90 SCA specimens were resistant to successive cyclic loads.

Effect of temperature on the mechanical properties of 3D-printed PLA tensile specimens

PurposeRecent advancements of 3D printing technology have brought forward the interest for this technique in many engineering fields. This study aims to focus on mechanical properties of the polylactic acid (PLA) feeding material under different thermal conditions for a typical fusion deposition of 3D printer system.Design/methodology/approachSpecimens were tested under static loading within the range 20ºC to 60ºC considering different infill orientations. The combined effect of temperature and filament orientation is investigated in terms of constitutive material parameters and final failure mechanisms. The difference between feeding system before and post-3D printing was also assessed by mechanical test on feeding filament to verify the thermal profile during the deposition phase.FindingsThe results in terms of Young’s modulus, ultimate tensile strength (UTS), strain at failure (εf) and stress at failure (σf) are presented and discussed to study the influence of process settings over the final deposited material. Fracture surfaces have been investigated using an optical microscope to link the phenomenological interpretation of the failure with the micro-mechanical behaviour. Experimental results show a strong correlation between stiffness and strength with the infill orientation and the temperature values. Moreover, a relevant effect is related to deformed geometry of the filament approaching glass transition region of the polymer according to the deposition orientation.Research limitations/implicationsThe developed method can be applied to optimise the stiffness and strength of any 3D-printed composite according to the infill orientation.Practical implicationsTo avoid the failure of specimens outside the gauge length, a previously proposed modification to the geometry was adopted. The geometry has a parabolic profile with a curvature of 1,000 mm tangent to the middle part of the specimen.Originality/valueSeveral authors have reported the stiffness and strength of 3D-printed parts under static and ambient temperature for different build parameters. However, there is a lack of literature on the combination of the latter with the temperature effects on the mechanical properties which this paper covers.

Compressive and Tensile Behavior of 3D-Printed and Natural Sandstones

The presented work compares the mechanical behavior from standard unconfined compressive strength and indirect tensile strength tests of natural sandstone and artificial sand-based specimens created by 3D additive manufacturing. Three natural sandstones of varying strength and stiffness were tested to capture a wide range of behavior for comparison with the 3D-printed specimens. Sand grains with furan and silicate binders, as well as, ceramic beads with silicate binder were 3D-printed by commercial suppliers. The tensile and compressive strength, the stiffness, the crack initiation and the crack damage thresholds and the strain behavior were examined to determine if the mechanical behavior of the 3D-printed specimens is similar to natural sandstones. The Sand-Furan 3D-prints behaved the closest to the weak natural sandstone. The compressive strength-to-stiffness ratio, also known as the modulus ratio, and the compressive-to-tensile strength ratio of the 3D-printed Sand-Furan specimens were found to be similar to the natural sandstones tested in this study and literature values. The failed specimens composed of ceramic beads with silicate binder, both in compression and tension, showed fracture growth not commonly observed in natural specimens. The other 3D-printed specimens generally fractured in a similar manner to natural specimens, although several of the quartz sand with furan binder specimens showed fracturing behavior similar to high porosity natural specimens. Over all, using the commercially available quartz sand with furan binder 3D-print materials showed promise to be able to replicate natural rock specimen behavior.

Effect of layer thickness on surface properties of 3D printed materials produced from wood flour/PLA filament

When the 3D printed materials are used as substrate for thin overlays or liquid surface coatings, their surface roughness and wettability play an important role in determining the quality of the final product. In this study, effect printing layer thickness on surface roughness and wettability of 3D printed samples made from wood flour/PLA filament having 1.75 mm was investigated. For this aim, four different printing layers, 0.05 mm, 0.1 mm, 0.2 mm, and 0.3 mm, were used in the production of the 3D-printed specimens. Average roughness (Ra), mean peak-to-valley height (Rz), and maximum peak-to-valley height (Ry) were considered to evaluate the surface characteristics of the specimens. The surface properties of the specimens were determined by using a stylus profilometer (Mitutoyo SJ-301). The wetting behavior of the specimens was characterized by the contact angle method (goniometer technique). The surface smoothness of the specimens significantly improved with decreasing printing layers. The wettability of the specimens significantly increased with increasing printing layer thickness.