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Additive manufacturing (AM) is a sustainable and innovative manufacturing technology to fabricate products with specific properties and complex shapes for additive manufacturable materials including polymers, steels, titanium, copper, ceramics, composites, etc. This technology can well facilitate consumer needs on products with complex geometry and...
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... Due to weak interlayer adhesion forces, material failure might occur in the direction of these gaps, which may result in varying features of polymer-printed objects related to the number of layers used. Depending on the AM technology 3D-printed objects may show an anisotropic behavior because the build angle on the printing platform influences the number of layers and, therefore, printing time [25][26][27]. ...
The aim of this study is to investigate the influence of printing material, build angle, and artificial aging on the accuracy of SLA-and DLP-printed occlusal devices in comparison to each other and to subtractively manufactured devices. A total of 192 occlusal devices were manufactured by one SLA-printing and two DLP-printing methods in 5 different build angles as well as milling. The specimens were scanned and superimposed to their initial CAD data and each other to obtain trueness and precision data values. A second series of scans were performed after the specimens underwent an artificial aging simulation by thermocycling. Again, trueness and precision were investigated, and pre-and post-aging values were compared. A statistically significant influence was found for all main effects: manufacturing method, build angle, and thermocycling, confirmed by two-way ANOVA. Regarding trueness, overall tendency indicated that subtractively manufactured splints were more accurate than the 3D-printed, with mean deviation values around ±0.15 mm, followed by the DLP1 group, with ±0.25 mm at 0 degree build angle. Within the additive manufacturing methods, DLP splints had significantly higher trueness for all build angles compared to SLA, which had the highest mean deviation values, with ±0.32 mm being the truest to the original CAD file. Regarding precision, subtractive manufacturing showed better accuracy than additive manufacturing. The artificial aging demonstrated a significant influence on the dimensional accuracy of only SLA-printed splints.
... improve material utilization [5]. More importantly, multi-axis printing is expected to achieve more uniform material distribution, so that the material deposition path is no longer limited to a fixed direction, reducing the anisotropy problem of the part, thereby improving mechanical isotropy [6]. Although multi-axis 3D printing increases the complexity of motion control and path planning, it provides new solutions to improve some of the major drawbacks derived from the additive manufacturing process. ...
Multi-axis 3D printing has emerged as a key solution to the challenges associated with the strength, anisotropy, and fabrication of large-scale structures in material-deposition-based 3D printing processes. In view of the rapid progress in this field, this article summarizes the unified workflow of multi-axis 3D printing and provides an overview, comparison, and review of the latest technologies and implementation mechanisms used in each stage. The main issues and challenges currently faced in this field are identified to provide references for future research.
... This variability can significantly impact the behavior of the material and, consequently, its properties on different axes. In 3D printing, anisotropy primarily manifests in three key dimensions: mechanical, electrical, and chemical properties [41]. For example, in FDM, this phenomenon is attributed to factors such as air voids, raster angles, and imperfect bonding conditions [41]. ...
... In 3D printing, anisotropy primarily manifests in three key dimensions: mechanical, electrical, and chemical properties [41]. For example, in FDM, this phenomenon is attributed to factors such as air voids, raster angles, and imperfect bonding conditions [41]. Most of these factors VOLUME 11, 2023 5 This article has been accepted for publication in IEEE Access. ...
... Most of these factors VOLUME 11, 2023 5 This article has been accepted for publication in IEEE Access. This is the author's version which has not been fully edited and are influenced by the printing direction and can affect properties such as toughness, hardness, bending, and proneness to fracture [42], as well as changes in permittivity ( Fig. 2) [41], [43], to name a few. ...
This article offers a thorough review of the current state-of-the-art in four-dimensional (4D) printed antennas and possible adaptable designs. It provides a succinct examination of various categories of materials used in three-dimensional (3D) and 4D printing, including the utilization of smart materials available in both printable and synthesized forms. The review encompasses a concise analysis of fabrication techniques, stimuli, and response behaviors applied in various types of smart materials. These materials have the potential to fabricate antennas with tunable and reconfigurable properties, including frequency of operation, bandwidth, gain, and radiation pattern. Given the novelty of applying 4D printing in antenna technologies, the review also considers additional reconfigurable antennas with mechanically tunable properties, as well as those in non-printed formats. This exploration hints at potential adaptations to the latter for the development of 4D printed antennas. The utilization of 4D printing presents a complex yet intriguing approach to antenna fabrication, offering the possibility of creating dynamic antennas with sophisticated characteristics.
... It is well known that AM materials suffer from anisotropic behaviour, because of the layer-by-layer manufacturing technique [105]. The printed parts are directionally dependent, and discontinuities can make the parts weak in the direction perpendicular to the print direction [106]. Multiple material properties can be affected by the direction of the printing [105,107], e.g., strength, elasticity, tensile properties, compression, and ductility. ...
Additive manufacturing (AM) is a field with both industrial and academic significance. Computer-aided optimisation has brought advances to this field over the years, but challenges and areas of improvement still remain. Design to execution inaccuracies, void formation, material anisotropy, and surface quality are examples of remaining challenges. These challenges can be improved via some of the trending optimisation topics, such as artificial intelligence (AI) and machine learning (ML); STL correction, replacement, or removal; slicing algorithms; and simulations. This paper reviews AM and its history with a special focus on the printing process and how it can be optimised using computer software. The most important new contribution is a survey of the present challenges connected with the prevailing optimisation topics. This can be seen as a foundation for future research. In addition, we suggest how certain challenges can be improved and show how such changes affect the printing process.
... The thickness of each plate was assessed by measuring the sample at several points with a micrometer screw gauge. The anisotropy of the samples, resulting from their layer-by-layer fabrication in two build orientations [25][26][27] are an important parameter. One part is obtained with its longitudinal axis in the z-axis (orthogonal to the build plate ( Fig. 2a)), the other in the x-axis (parallel to the build plate (Fig. 2b)). ...
The method of Directed Energy Deposition of polymers (DED-LB/P) was extended to allow control over the melt pool temperature using a pyrometer. DED-LB/P was used to build test specimen of polyamide 12 (PA12), orthogonal and parallel to the long side. Samples prepared under temperature control show superior mechanical properties over those generated without. The temperature of the melt pool allows to tune the quality of the built part. A too low temperature leads to a porous part on account of insufficient powder fusion, and a too high temperature leads to holes by formation of volatiles. The mechanical properties can be related to the porosity, the molecular mass of PA12 did not change substantially, the distribution width however increased with temperature. The best processing conditions were at 220 °C leading to a build part with a porosity of 0.6%, a Youngs modulus of 550 MPa and a fracture-strain of 15% with an ultimate strength of almost 28 MPa.
... Unfortunately, additive technology is not without its disadvantages, one of which is the anisotropy of mechanical properties. This aspect is extremely important, as designers and manufacturers of 3D printed parts that are expected to function under certain loads must choose the right printing parameters to achieve the highest possible strength and thus longer product life [3]. ...
... Previous investigation on build orientation with AM resins have shown that the orientation of the individual layers during the printing process has an effect on the mechanical characteristics of the devices that are printed [23,24]. Earlier studies [33,34] have described an anisotropy of additive materials that is brought about by the orientation during the printing process. When employing a DLP printer, a collection of micro-mirrors is exposed to ultraviolet light, which simultaneously polymerizes a layer that is composed of a large number of voxels. ...
One therapeutical alternative in the treatment of functional disorders is the use of printed oral splints. The mechanical properties of these materials are highly essential to their clinical effectiveness, and their performance may vary depending on factors such as cleaning, post-polymerization, or their orientation during construction. The objective of this in vitro investigation is to evaluate the effectiveness of the selected materials in terms of their biaxial flexural strength in relation to the criteria listed above. Splint materials were used in the printing of 720 discs. The printing process was carried out in different orientations in relation to the building platform. Either an automatic or manual cleaning process was performed on the samples. For post-polymerization, either an LED or Xenon light was utilized. A piston-on-three-ball test was used to measure the biaxial flexural strength (BFS) of the materials after they were stored in water for either 24 h or 60 days. The homogeneity of the data was controlled by employing the Levene method, and the differences between the groups were analyzed using the ANOVA and Bonferroni methods. After being stored for twenty-four hours, the mean BFS ranged anywhere from 79 MPa to 157 MPa. Following a period of sixty hours, the BFS exhibited a substantial drop and revealed values that ranged from 72 to 127 MPa. There was no significant difference that could be identified between the materials or between the various cleaning processes. The results of post-polymerization showed that the LED light produced higher means than the Xenon light did. In terms of position, the mean values varied greatly, with 0°’s mean value being 101 MPa, 45°’s mean value being 102 MPa, and 90°’s mean value being 115 MPa. The use of a build orientation of 90° and post-polymerization with LED light resulted in significantly increased biaxial flexural strength. According to this study, this design should be implemented in order to ensure that splint materials have the highest possible strength.
... A drawback to the use of tooling made from thermoplastic composites is the difficulty in uniform heating of the mold because of the poor thermal conductivity of the mold material. The thermal conductivity of the composites is highly anisotropic [15][16][17]. The difficulty with heating such molds was documented in a recent study reported by Bogdanor et al. [18]; in this work, they printed a mostly planar mold from polyether-sulfone reinforced with 25 wt% carbon fibers, using a print direction aligned with the mold surface. ...
The spring-in phenomenon or reduced angle observed in a molded composite part with angled sides or an L-shape is commonly attributed to material anisotropy in the molded part and mismatched thermal expansion between the conventional metal tool and the molded part. This paper investigates the distortion and spring-in of a compression molded carbon fabric reinforced epoxy composite part with angled sides, using composite tooling that is made by extrusion deposition additive manufacturing (EDAM). The composite tooling was made from carbon fiber reinforced polyetherimide (ULTEM) by EDAM; as a result, material anisotropy existed in both tooling and molded part. In the present study, a uniform vertical orientation was used during the extrusion deposition printing of the mold, in order to promote heat transfer along the press closing direction. The thermomechanical properties were measured for the tooling material from EDAM-printed plaques and for the composite part material from molded plaques; the measured inputs were then used in simulation of mold deformation, residual stresses, and part distortion. The spring-in predicted for the part molded with the EDAM tool was 1.4°, which is close to the experimentally measured spring-in of 1.3°. The spring-in predicted for a similar molding cycle with the steel mold was much higher at 2.6°.
... In 1986, Chuck (Charles) Hull claimed the discovery of this method [6]. The main advantage of AM to conventional forming and subtractive manufacturing is its ability to generate complex geometries and limit the amount of waste material [7][8][9]. Industries such as automotive, aerospace, and healthcare showed the potential of using AM methods for generating complex, lightweight parts with acceptable performances. The architectural industry by prototyping the small models to the entire building can also gain a huge benefit in saving time and costs in production [4,[9][10][11]. ...
... Industries such as automotive, aerospace, and healthcare showed the potential of using AM methods for generating complex, lightweight parts with acceptable performances. The architectural industry by prototyping the small models to the entire building can also gain a huge benefit in saving time and costs in production [4,[9][10][11]. ...
... However, the simplest method that is capable of generating complex geometries, producing less waste and using the relatively cheapest equipment and raw material is 2 of 26 fused deposition modelling (FDM) [12], or fused filament fabrication (FFF). Thermoplastic materials, including acrylonitrile butadiene styrene (ABS), high-impact polystyrene (HIPS), nylon, polycarbonate (PC), polyethylene (PE), polyether ether ketone (PEEK), polyethylene terephthalate glycol-modified (PETG), polylactide (PLA), polyoxymethylene (POM), polypropylene (PP), and polyvinyl alcohol (PVA), can be used in conjunction with the FDM method to obtain parts with different mechanical properties [9,[13][14][15]. Figure 1 shows a schematic of the typical FDM process. Since the variation in distinct 3D printing process parameters like layer thickness, raster angle, nozzle temperature [16], infill pattern [17], and infill density can strongly modify the parts' properties, understanding their influence is a crucial step to guarantee high-quality 3D-printed products. ...
Thermoplastic polymers are widely used in industry to generate parts with reasonable production costs, lightweight, chemical stability, sustainability, and recyclability compared to other materials such as metals, metalloids, or even thermoset polymers. The innovative additive manufacturing (AM) techniques, e.g., fused deposition modelling (FDM), can be used to fabricate thermoplastic products with complex geometries and specific properties. However, the mechanical integrity of those FDM-printed plastic parts can be greatly impacted by a phenomenon named material anisotropy. In this study, an experimental study on a popular 3D printing polymer material-acrylonitrile butadiene styrene (ABS)-is performed to determine how FDM process parameters affect the mechanical properties of the printed ABS parts. This study uniquely concentrates on investigating mechanical anisotropy in FDM-printed ABS, delving into a combination of key printing parameters for a comprehensive exploration. Meanwhile, a finite-element-based numerical analysis is also utilised to numerically evaluate the influences of infill percentage and build orientations on the mechanical properties of the 3D-printed ABS materials for comparison. It generates a better understanding of material anisotropy and helps to find the optimal FDM process parameters to print high-quality ABS parts and may attract industrial interests in transitioning from traditional ABS part production methods such as injection moulding or hot pressing to additive manufacturing.
... Various techniques have been developed since the emergence of technology. [1] In the last decade, the mechanical characteristics of printed parts have significantly increased, making it feasible to directly create completed components that are fit for certain applications. Nevertheless, 3D printing methods are often confined to limited build quantities, exhibit slow deposition rates, and are costly compared to conventional methods. ...
This research investigated the effect of layer-building time on the interlayer adhesion strength of polymer additive manufacturing. Many methods have been developed for polymer additive manufacturing and Fused Deposition Modeling (FDM) is the most common type of polymer extrusion-based. FDM uses layer-by-layer building mechanisms to manufacture the products resulting in weak adhesion strength between layers in the building direction (z-axis). This causes mechanical performance variations in printed parts’ x, y, and z-axis. Longer layer-building time increases heat dissipation, making it more probable that large-scale products may be affected by weak interlayer adhesion issues. Small-scale 3D printing has advanced significantly, with researchers testing and applying the technology to various industrial sectors. Yet, a significant amount of work still has to be done on research into Big Area Additive Manufacturing BAAM intended for large-scale applications such as building and car manufacturing. This field needs further and extensive research to understand related challenges. Therefore, this work investigated the effect of layer-building time on interlayer adhesion strength. 2500 HP PLA was used in this investigation to print samples with four different layer-building times 30, 90, 150, and 210 seconds. Printed samples were prepared for flat-wise tensile testing (FTT) in a tensile machine. Results showed that interlayer adhesion strength weaken with increasing the layer-building time.
