Raster Orientation Research Articles

Investigating the effect of orientation, infill density with Triple raster pattern on the tensile properties for 3D Printed samples

The main objective of this study is to characterize the effect of infill percentage, printing orientation and raster angle on ABS samples prepared with 3D printing technology. In this research, samples used were fabricated with two different infill percentages (50% & 75%), 6 different raster patterns and three different orientations. The influence of these parameters on tensile properties were studied with the help of 3D printed samples as per ASTM standard D638 Type IV. From the experimental analysis it was found that the tensile properties were highly anisotropic. Stress strain graphs are plotted for all the samples and the variation of strength with respect to the three parameters are analysed. It was observed that Infill density is directly proportional to mechanical properties. Flat and vertical orientation have better strength and stiffness in comparison with vertical build. The experimental results proved that flat oriented samples exhibited variable strength for changes in raster orientation, other samples have shown minimal changes only.

Effect of fused deposition modeling process parameters on the mechanical properties of recycled polyethylene terephthalate parts

AbstractFused deposition modeling (FDM) filaments made of recycled materials are desirable for environmentally friendly and sustainable manufacturing of prototypes and load‐bearing components in many applications. We investigate the effect of FDM process parameters on the mechanical properties of 3D‐printed parts made of recycled polyethylene terephthalate (rPET) filaments. Increasing the nozzle temperature from 230°C to 260°C improves the strength of the specimens by 100%. Using a raster orientation parallel to the loading direction improves the ductility by more an order of magnitude. Specimen orientation and infill ratio also influence the mechanical properties. The temperature and the orientation effects are related to the quality of fusion between the printed lines. A modified Gibson‐Ashby model correctly predicts the strength as a function of the infill ratio. Through the optimization of process parameters, the mechanical strength of 3D‐printed rPET structures can reach that of injection‐molded PET, making FDM a suitable manufacturing technique for load‐bearing applications.

3D printing: An appealing route for customized drug delivery systems.

In the recent decade, three-dimensional (3D) printers started to grow strongly in the field of drug delivery and personalized medicine, as they can tailor dosage forms according to the needs of each individual. This review gives an overview on the basic principles of layer-by-layer building of pharmaceutical dosage forms using different types of 3D printers. Also, the effect of infill percentage and pattern, raster orientation, layer thickness, thermal processing parameters on the printed formulations is highlighted. Additionally, the complex designs constructed by the 3D printers in order to modify the product shape, density, mucoadhesion and drug release are recapitulated. This review summarizes numerous applications for 3D printing in building drug-loaded structures including tablets, scaffolds, implants, microneedles, capsules, films, hydrogels, mouthguards, tubes, stents, vaginal suppositories and rings as well as in pediatric field. Finally, we suggest further investigational researches to aid in the widespread of 3D printing in the industrial pharmaceutical field. The 3D printing technology is expected to revolutionize drug delivery systems through customization of pharmaceutical formulations.

The influence of in-plane raster angle on tensile and fracture strengths of 3D-printed PLA specimens

The present paper studies the effect of in-plane raster orientation on the tensile and fracture strengths of poly-lactic acid (PLA) samples made by fused deposition modeling technique. Four different raster angles of 0/90°, 15/−75°, 30/−60°, and 45/−45° are selected for the dog-bone and the semi-circular bending (SCB) specimens to investigate the tensile and mode I fracture behavior of the 3D-printed PLAs. The results demonstrate anisotropic behavior in the both tensile and fracture properties of the material. Additionally, due to the plastic deformations of the material prior to the fracture initiation load, the J-integral is selected as the fracture characterizing parameter. To do so, some elastic-plastic finite element simulations were performed to obtain the critical values of J-integral. The raster orientation of 45/−45° exhibits the best performance with maximum percent elongation and fracture resistance compared with the three other raster angles. While the critical J-integral of 45/−45° sample is 6815 J/m2, this value is 1839 J/m2 for 0/90° sample. In addition, in the samples used for fracture tests, the crack growth path is investigated to analyze the effect of raster orientation on the fracture trajectories of the SCB specimens. Based on the observed crack growth trajectories, the difference between the fracture loads and the amounts of plastic deformation in the SCB samples with different raster orientations are justified. Finally, the scanning electron microscopy (SEM) is utilized to explore the failure mechanism in the dog-bone samples.

Evaluating FDM Process Parameter Sensitive Mechanical Performance of Elastomers at Various Strain Rates of Loading

To optimize the mechanical performance of fused deposition modelling (FDM) fabricated parts, it is necessary to evaluate the influence of process parameters on the resulting mechanical performance. The main focus of the study was to characterize the influence of the initial process parameters on the mechanical performance of thermoplastic polyurethane under a quasi-static and high strain rate (~2500 s−1). The effects of infill percentage, layer height, and raster orientation on the mechanical properties of an FDM-fabricated part were evaluated. At a quasi-static rate of loading, layer height was found to be the most significant factor (36.5% enhancement in tensile strength). As the layer height of the sample increased from 0.1 to 0.4 mm, the resulting tensile strength sample was decreased by 36.5%. At a high-strain rate of loading, infill percentage was found to be the most critical factor influencing the mechanical strength of the sample (12.4% enhancement of compressive strength at 100% as compared to 80% infill). Furthermore, statistical analysis revealed the presence of significant interactions between the input parameters. Finally, using an artificial neural networking approach, we evaluated a regression model that related the process parameters (input factors) to the resulting strength of the samples.

Investigate the effects of process parameters on material properties and microstructural changes of 3D-printed specimens using fused deposition modelling (FDM)

ABSTRACT One of the most significant parameters of the Fused Deposition Modelling (FDM) for 3D printing process is the raster angle. In this study, the five different raster angles are used to fabricate the 3D parts using thermoplastic material - polylactic acid (PLA), and tensile properties of these parts are investigated to identify the best raster position to fabricate the strongest 3D printing part. In this study, the microstructural analyses on fracture interface, and on outer and inner surfaces of these 3D parts are performed using a scanning electron microscopy (SEM) to examine material failure modes and reasons, and defects in the 3D parts. This study identified the best raster orientation to lie down the layers of 3D printing material during the process. This study also identified that there are several defects in 3D printed parts at micro level that have large impact on mechanical properties of 3D printed part.

Mechanical evaluation of polymeric filaments and their corresponding 3D printed samples

3D printing technologies permits to produce functional parts with complex geometries, optimized topologies or enhanced internal structures. The relationship between mechanical performance and manufacturing parameters should be exhaustively analyzed to warrant the long term success of printed products. In this work, the mechanical performance of filaments based on acrylonitrile butadiene styrene (ABS), polylactic acid (PLA) and polylactic acid/polyhydroxyalkanoate (PLA/PHA) was investigated and also compared with their corresponding 3D printed samples. In general, the specimen dimensional deviations were found to be within the tolerances defined by the standard testing protocols. Density values revealed a high level of filament fusion promoting a nearly solid internal structure. The filaments exhibited improved tensile performance with respect to their corresponding printed samples. Tensile and bending performance looked quite independent of the raster angle. Izod impact behavior was increased, for ABS systems printed with the ±45° raster orientation. Quasi-static fracture tests displayed improved crack initiation resistance with the 0°/90° raster angle. The crack propagation observed for the ±45° specimens, through the bonding of the inter-layers, suggests weak entanglements.

Investigation of 3D‐printed PLA–stainless‐steel polymeric composite through fused deposition modelling‐based additive manufacturing process for biomedical applications

AbstractAmong the several 3D printing technologies, fused deposition modelling (FDM) is gaining popularity because it can fabricate geometrically complex shapes of polymeric bio‐implants at reasonable quality and cost mainly due to lower cost of FDM‐based 3D printers as well as the filament form of feedstock material. Particularly, to cater the need of cost‐effective biomedical applications, both poly(lactic) acid (PLA) and stainless‐steel materials individually displayed the biocompatibility for various biomedical applications. The pure polymeric components are generally lower in mechanical strength, but these limitations can be resolved by developing a polymer–metallic composite; therefore, the recently developed PLA–stainless‐steel composite was selected for the present work. This is new material and the current literature lacks in providing the necessary FDM processing parameters to obtain desired functional properties of PLA–stainless‐steel components with unaltered biocompatibility. Therefore, the objective here is to obtain the optimized processing parameters through the design of experiments that shows the desired functional properties of PLA–stainless‐steel specimens manufactured by FDM and later validate the structural strength through the tensile and impact tests. It was observed that the PLA–stainless‐steel composite has a toughness of 18 kJ/m2 and has an ultimate tensile strength of ~69 MPa at 45° and ~23 MPa at 90° raster orientation of the print. Biocompatibility of the PLA–stainless‐steel polymeric composite was assessed using pre‐osteoblast cells, and materials were found to have biocompatibility unchanged from pure PLA. Overall, it was proved from this work that the low‐cost desktop FDM printer can be numerically optimized using statistical analyses to fabricate the next‐generation biomaterials for biomedical implants with tailored dimensions and surface finish with required mechanical strength and biocompatibility.

Direct 3D Printing of Highly Anisotropic, Flexible, Constriction-Resistive Sensors for Multidirectional Proprioception in Soft Robots.

A key missing technology for the emerging field of soft robotics is the provision of highly selective multidirectional tactile sensing that can be easily integrated into a robot using simple fabrication techniques. Conventional strain sensors, such as strain gauges, are typically designed to respond to strain in a single direction and are mounted on the external surface of a structure. Herein, we present a technique for three-dimensional (3D) printing of multidirectional, anisotropic, and constriction-resistive strain sensors, which can be directly integrated into the interior of soft robots. Using a carbon-nanotube-reinforced polylactic acid (PLA-CNT), both the sensing element and the conductive interconnect of the sensor system are 3D-printed. The sensor's sensitivity and anisotropy can be adjusted by controlling the air gap between printed adjacent tracks, infill density, and build orientation relative to the main loading direction. In particular, sensors printed with a near-zero air gap, i.e., adjacent tracks forming a kissing bond, can achieve a gauge factor of ∼1342 perpendicular to the raster orientation and a gauge factor of ∼1 parallel to the raster orientation. The maximum directional selectivity of this ultrasensitive sensor is 31.4, which is approximately 9 times greater than the highest value reported for multidirectional sensors so far. The high sensitivity stems from the progressive opening and closing of the kissing bond between adjacent tracks. The potential of this type of sensors and the simple manufacturing process are demonstrated by integrating the sensor with a soft robotic actuator. The sensors are able to identify and quantify the bending deformation and angle in different directions. The ability to fabricate sensors with tailored footprints and directional selectivity during 3D printing of soft robotic systems paves the way toward highly customizable, highly integrated multifunctional soft robots that are better able to sense both themselves and their environments.

Influence of raster orientation on the determination of fracture properties of polypropylene thin components produced by additive manufacturing

Additive manufacturing techniques are increasingly being used to produce components in different sectors, including industrial, aeronautical, education and medical applications. In order to predict the mechanical behaviour of these components, it is necessary to characterise materials according to their manufacturing process. Considering the technology of additive manufacturing by “fused filament fabrication” (FFF) or “fused deposition modelling” (FDM), and specifically in “material extrusion additive manufacturing” (ME-AM), several parameters must be defined to produce the required geometries. The infill orientation is one of the parameters that most affects mechanical and fracture properties of the final components, often causing premature failures. Therefore, the objective of this work is to study the influence of raster orientation on fracture parameters for thin polymer components. For this purpose, double deeply edge-notched tensile (DDEN-T) thin specimens have been tested considering the essential work of fracture (EWF) approach. The studied material has been polypropylene (PP). Experimental results show the influence of filament orientation on the essential work of fracture and the limitations of the EWF approach for some of the assessed orientations. Additionally, two different fracture mechanisms have been observed and discussed. This work demonstrates the importance of optimising the raster orientation during the filament deposition layer by layer, depending on the application of the manufactured component, to preserve its structural integrity.

Optimization of printing parameters for improvement of mechanical and thermal performances of 3D printed poly(ether ether ketone) parts

AbstractMany processing parameters can be adjusted to optimize the fused filament fabrication (FFF) process, a popular and widely used additive manufacturing techniques for plastic materials. Among those easily adjusted parameters are the nozzle temperature, printing speed, raster orientation, and layer thicknesses. Using poly(ether ether ketone) (PEEK) as the base material, a design of experiments analysis was performed on the main FFF parameters. A response surface methodology was applied to analyze the results and to maximize the output responses. Results have shown that the nozzle temperature is the most influential parameter on tensile properties and the crystallinity degree of printed PEEK by FFF process. Parts produced with optimized FFF parameters were then subjected to an annealing treatment to induce a relaxation of residual stress and to enhance crystallinity. The best properties for 3D printed PEEK parts were achieved with annealed parts prepared at 400°C with a printing speed of 30 mm/s, 0.15 mm layer thickness and raster orientation of [0°/15°/−15°]. The resulting parts have mechanical properties comparable to those of injected PEEK.

Finite element simulation of tensile test of composite materials manufactured by 3D printing

A principle of 3D printing is based on formation of continuous layers of materials up to a formation of the final shape. Materials for production of given components are composite materials, especially on the basis of so-termed CFRP, CRP, (carbon fibre – so-termed polymers reinforced by carbon fibres). The objective of this paper is to predict the deformation length of carbon/onyx composite laminates using Finite Element Analysis (FEA) and compare with universal testing machine INOVA FU 160 deformation results through the tensile load. Specimen were printed at raster orientation angles of 0°, 45° and 90° to test orientation effects on part strength. 16 ply CFRP specimens with various stacking sequences were analysed for their strength and displacements. A shell model has been established for simulation of the tensile test composite specimen which enables to understand the mechanical strength and strain at failure of the composite materials. The simulations of experiment are provided in FEM program ANSYS and ANSYS/Workbench.

Prediction of in-plane stiffness of multi-material 3D printed laminate parts fabricated by FDM process using CLT and its mechanical behaviour under tensile load

The use of fused deposition modeling (FDM) process in the making of the multi-material 3D printed part is adding a new dimension in the area of additive manufacturing technology. This paper highlights the procedures to print bi-material laminate parts with different raster orientation by applying FDM technique and describe its mechanical behaviour using classical laminate theory (CLT). For excellent thermal diffusion and substantial functionalities, polylactic acid (PLA) and polylactic acid carbon black (PLA CB) were selected as feedstock materials for printing bi-material structure. The theoretical in-plane stiffness of 3D printed bi-material laminate parts was calculated by using the philosophy of CLT, and the result was validated against experimental value. Fourier-transform infrared spectroscopy (FTIR) study on feedstock filament materials and 3D printed samples ascertained the cause for molecular degradation in printed parts. Furthermore, at different raster orientation, the average tensile properties like tensile stiffness, ultimate tensile strength(UTS) and breaking strain of 3D printed bi-material laminate parts were investigated and compared with mono-material laminate models. Fractography analysis of failure surfaces of bi-material laminates was done by scanning electron microscope(SEM) to explore the nature of failure under tensile loading.

Effect of extrusion temperature on fused filament fabrication parts orthotropic behaviour

PurposeThe purpose of this paper is to verify the effects of extrusion temperature on orthotropic behaviour of the mechanical properties of parts obtained by fused filament fabrication (FFF) under quasi-static tensile loads.Design/methodology/approachTensile tests were performed on single layer specimens fabricated in polylactic acid (PLA) and acrylonitrile butadiene styrene (ABS) to evaluate the mechanical properties at different extrusion temperatures and raster orientations (0°, 45° and 90°). Furthermore, a detailed study of morphological characteristics of the single layer samples cross-section and of the bonding quality among adjacent deposited filaments was performed by scanning electron microscopy to correlate the morphology of materials with mechanical behaviour.FindingsThe results show that the orthotropic behaviour of FFF-printed parts tends to reduce, while the mechanical properties improved with increase in extrusion temperature. Furthermore, the increase in extrusion temperature led to an improvement in inter-raster bonding quality and in the compactness and homogeneity of the parts.Originality/valueThe relation between the extrusion temperature, orthotropic behaviour and morphological surface characteristics of the single layer specimen obtained by FFF has not been previously reported.

Stiffness prediction of 3D printed fiber-reinforced thermoplastic composites

PurposeThe purpose of this study is to confirm that the stiffness of fused filament fabrication (FFF) three-dimensionally (3D) printed fiber-reinforced thermoplastic (FRP) materials can be predicted using classical laminate theory (CLT), and to subsequently use the model to demonstrate its potential to improve the mechanical properties of FFF 3D printed parts intended for load-bearing applications.Design/methodology/approachThe porosity and the fiber orientation in specimens printed with carbon fiber reinforced filament were calculated from micro-computed tomography (µCT) images. The infill portion of the sample was modeled using CLT, while the perimeter contour portion was modeled with a rule of mixtures (ROM) approach.FindingsThe µCT scan images showed that a low porosity of 0.7 ± 0.1% was achieved, and the fibers were highly oriented in the filament extrusion direction. CLT and ROM were effective analytical models to predict the elastic modulus and Poisson’s ratio of FFF 3D printed FRP laminates.Research limitations/implicationsIn this study, the CLT model was only used to predict the properties of flat plates. Once the in-plane properties are known, however, they can be used in a finite element analysis to predict the behavior of plate and shell structures.Practical implicationsBy controlling the raster orientation, the mechanical properties of a FFF part can be optimized for the intended application.Originality/valueBefore this study, CLT had not been validated for FFF 3D printed FRPs. CLT can be used to help designers tailor the raster pattern of each layer for specific stiffness requirements.

On the strain-life fatigue parameters of additive manufactured plastic materials through fused filament fabrication process

In this paper, the effects of part build directions or raster orientations have been studied on the strain-life fatigue parameters of a wide range of 3D printed plastic materials. These materials have been manufactured through Fused Filament Fabrication (FFF), also known under its trademarked name Fused Deposition Modeling (FDM). To do so, precise analyses of fatigue data with the Ramberg-Osgood form of stress-strain curves were utilized through a strain-based approach to fatigue. The effects of different load ratios and types of loading on fatigue parameters have also been studied. Materials considered in this study were Ultem 9085, Polycarbonate (PC), and Polylactic Acid (PLA). Additive manufactured plastic parts that are FDM-processed exhibited large anisotropy of strain-life fatigue parameters. Hence, the upper and lower bounds for fatigue life prediction were introduced based on the strongest and weakest part build directions or raster orientations of 3D printed materials. For all materials studied in the present paper, fill densities, which seem to have significant impact on fatigue strength of 3D printed parts, have been selected based on the maximum fatigue strength of each part. Results showed that, in some build orientations, the transition fatigue life does not exist. In other orientations, in which the plastic strain components are high enough, transition fatigue lives vary roughly between 20–400 cycles. This means that if the part design in very low cycle fatigue regime is of interest, plastic strains and more complicated plasticity analysis are needed. Results show that the load ratio has no major impact on the fatigue parameters of 3D printed PC parts. In addition, changing in the loading type from tensile fatigue to rotating bending fatigue can significantly impact the fatigue strength coefficient of 3D printed PLA specimens however, it does not noticeably alter the fatigue strength exponents.

Flexure Behaviors of ABS-Based Composites Containing Carbon and Kevlar Fibers by Material Extrusion 3D Printing.

Short-fiber-reinforced thermoplastics are popular for improving the mechanical properties exhibited by pristine thermoplastic materials. Due to the inherent conflict between strength and ductility, there are only a few successful cases of simultaneous enhancement of these two properties in polymer composite components. The objective of this work was to explore the feasibility of simultaneous enhancement of strength and ductility in ABS-based composites with short-carbon and Kevlar fiber reinforcement by material extrusion 3D printing (ME3DP). Microstructure characterization and measurement of thermal and mechanical properties were conducted to evaluate the fiber-reinforced ABS. The influence of printing raster orientation and build direction on the mechanical properties of material extrusion of 3D-printed composites was analyzed. Experimental results demonstrated that the reinforcement of the ABS-based composites by short-carbon and Kevlar fibers under optimized 3D-printing conditions led to balanced flexural strength and ductility. The ABS-based composites with a raster orientation of ±45° and side build direction presented the highest flexural behaviors among the samples in the current study. The main reason was attributed to the printed contour layers and the irregular zigzag paths, which could delay the initiation and propagation of microcracks.

Homogenisation of elastic properties in FDM components using microscale RVE numerical analysis

Fused deposition modelling (FDM) is an additive manufacturing method having the potential to fabricate functional components. As the inherent nature of additive structures, the component stiffness depends on the build parameters such as layer height and raster orientation in addition to the filament material properties. Even on FDM prints with 100% infill density, voids are formed along the interface of rasters and contribute to the characteristics of the component. The primary role of the present work is to determine elastic characteristics such as Young’s modulus, shear modulus and Poisson’s ratio of FDM components and study the effect of build parameters. The void geometry identified from the cross-sectional morphology was used to create a microscale representative volume element (RVE) model capturing the characteristics of the FDM print. The elastic constants of the microscale model RVE were estimated by volume average method and homogenised over the entire structure. The study also investigated the influence of layer height on the elastic behaviour of FDM components in two different raster orientations of 0° and 0°/90°. Both the conditions exhibited directional characteristics and the elasticity constants approaches filament characteristics with decreases in the layer height. The modulus of elasticity was found maximum in the direction of raster orientation, whereas the elasticity modulus along vertical direction exhibited the lowest. The components with 0°–90° raster orientation exhibited transversely isotropic characteristics. Thus, the actual cross-sectional morphology-based microscale numerical analysis can effectively predict the directional attributes of FDM prints.

Understanding the microstructural role of bio-sourced 3D printed structures on the tensile performance

This study aims at revealing the role of microstructural arrangement on the mechanical behaviour of printed PLA-Hemp using Fused Deposition Modelling (FDM). 3D printing is performed by varying the printing temperature. The laying down process is monitored using infra-red measurement. X-ray micro-tomography is used to acquire the 3D microstructure of printed PLA-Hemp. Tensile performance is determined by testing neat and notched specimens. Finite element modelling based on microstructure implementation is conducted to reveal the deformation mechanisms associated with the tensile loading. The results show a wide temperature range for printability of PLA-Hemp but overheating effects characterises the printing using large temperatures (>220 °C). The tensile performance is found dependent on the printing temperature, a modified filament morphology, and an imperfect nature of the hemp-PLA interface within the filament. Finite element results reveal particular characteristics of stress fields that superpose with underlined microstructure of filament arrangement. Despite this correlation, the low porosity level and the brittle nature of the filament do not allow strong dependence of the crack propagation on the raster orientation.

Investigation of fused deposition modeling processing parameters of 3D PLA specimens by an experimental design methodology

Abstract The main objective of this study is to analyze the tensile strength of PLA parts manufactured through fused filament fabrication (FFF) using a commercially available 3D printer. This study is primarily focused on the effects of the tensile strength of specimens subjected to the influence of four factors; layer thickness, fill density, raster orientation and sample structure type. A 2331 mixed-level factorial design approach was used, and the individual effects of the four main factors and their interactions determined. This experimental design had been implemented for two different infills: rectilinear and honeycomb. Specimens were printed at raster orientation angles of 30 °, 60 ° and 90 ° at a fill density of 50 % and 100 %. A layer thickness of 0.15 mm and 0.05 mm was chosen for printing the specimens. The samples were tested using a standard tensile testing machine with an extensometer to determine mechanical strength characteristics such as ultimate tensile strength, maximum force and maximum elongation. The data obtained was then analyzed using Minitab 13.20 software. The results showed that 30 ° raster orientation yields the highest mechanical properties at each individual layer when compared to 60 ° and 90 °. The fill density proves to be the most influential parameter on tensile strength, followed by the sample structure type. The results also found tensile strength to directly proporionate to layer thickness. By improving the material properties through the addition of layers as observed in the results, it will be possible to provide support for software developers, mechanical designers and engineers to reduce manufacturing time, material use and costs.