Horizontal Printing Research Articles

Modeling and self-supporting printing simulation of fuse filament fabrication

This study presented a comprehensive computational fluid dynamics-based model for fused filament fabrication (FFF) three-dimensional (3D) printing multiphase and multiphysics coupling. A model based on the framework of computational fluid dynamics was built, utilizing the front-tracking method for high precision of multiphase material interfaces, a fully resolved simulation at the mesoscale explores the underlying physical mechanism of the self-supported horizontal printing. The study investigated the influence of printing temperature and velocity on the FFF process, exhibiting a certain self-supporting forming ability over a specific range. The results indicated that during the printing of large-span horizontal extension structures, the bridge deck material transitions from initial straight extension to sagging deformation, ultimately adopting a curved shape. The straight extension distance is inversely proportional to the depth of the sagging deformation. Additionally, the study revealed that printing temperature primarily affected the curing time of the molten material, while printing velocity fundamentally affected the relaxation time of both thermal and dynamic characteristics of the material.

Evaluating the thermal, mechanical and swelling behavior of novel silicone and polyurethane additively manufactured O-rings in the presence of organic liquids and military fuels

This work investigates the physical properties and swelling behavior of additively manufactured (AM) and traditionally manufactured (TM) polyurethane (PU) and silicone O-rings when exposed to organic liquids and military fuels. Polymer properties were explored using differential scanning calorimetry, thermal gravimetric analysis, and tensile testing, and two AM print orientations (vertical and horizontal) were investigated. The AM polyurethane vertical and horizontal O-rings formed from a selective laser sintering (SLS) process had similar thermal features to each other and differed slightly from the un-sintered polymer in the temperature at which the greatest rate of mass loss occurred in the TGA analysis. The thermal features of the AM silicone O-rings formed using stereolithography (SLA) were more similar to those of a commercial soft silicone than to those of a commercial high purity silicone. The horizontal print orientation for each polymer had a higher tensile strength than its respective vertically oriented print. A 1-week exposure of the AM O-rings to the various organic liquids reduced the tensile strength of AM O-rings by as much as 80% (tensile strength exposed/tensile strength unexposed = 0.2). Polyurethane AM O-rings swelled from 3 to 74% with the greatest swelling occurring from exposure to acetone. Silicone AM O-rings swelled from 13 to 258% with the greatest swelling occurring from exposure to iso-octane. In general, the commercial O-rings swelled less than their AM counterparts, had higher tensile strengths, and had smoother surfaces. The maximum swelling for the PU O-rings occurred at an overall Hansen solubility parameter (HSP) between 18 and 20 MPa1/2, while the maximum for silicone occurred at an HSP of 14.3 MPa1/2. These values are consistent with literature values, which can vary widely.

Accuracy of additively manufactured and steam sterilized surgical guides by means of continuous liquid interface production, stereolithography, digital light processing, and fused filament fabrication

Different printing technologies can be used for prosthetically oriented implant placement, however the influence of different printing orientations and steam sterilization remains unclear. In particular, no data is available for the novel technology Continuous Liquid Interface Production. The objective was to evaluate the dimensional accuracy of surgical guides manufactured with different printing techniques in vertical and horizontal printing orientation before and after steam sterilization. A total of 80 surgical guides were manufactured by means of continuous liquid interface production (CLIP; material: Keyguide, Keyprint), digital light processing (DLP; material: Luxaprint Ortho, DMG), stereolithography (SLA; Surgical guide, Formlabs), and fused filament fabrication (FFF; material: Clear Base Support, Arfona) in vertical and horizontal printing orientation (n = 10 per subgroup). Spheres were included in the design to determine the coordinates of 17 reference points. Each specimen was digitized with a laboratory scanner after additive manufacturing (AM) and after steam sterilization (134 °C). To determine the accuracy, root mean square values (RMS) were calculated and coordinates of the reference points were recorded. Based on the measured coordinates, deviations of the reference points and relevant distances were calculated. Paired t-tests and one-way ANOVA were applied for statistical analysis (significance p < 0.05). After AM, all printing technologies showed comparable high accuracy, with an increased deviation in z-axis when printed horizontally. After sterilization, FFF printed surgical guides showed distinct warpage. The other subgroups showed no significant differences regarding the RMS of the corpus after steam sterilization (p > 0.05). Regarding reference points and distances, CLIP showed larger deviations compared to SLA in both printing orientations after steam sterilization, while DLP manufactured guides were the most dimensionally stable. In conclusion, the different printing technologies and orientations had little effect on the manufacturing accuracy of the surgical guides before sterilization. However, after sterilization, FFF surgical guides exhibited significant deformation making their clinical use impossible. CLIP showed larger deformations due to steam sterilization than the other photopolymerizing techniques, however, discrepancies may be considered within the range of clinical acceptance. The influence on the implant position remains to be evaluated.

Effect of Hydroxypropyl methyl cellulose (HPMC) on rheology and printability of the first printed layer of cement activated slag-based 3D printing concrete

Nowadays, Ground Granulated Blast Furnace Slag (GGBFS) is generally used to replace cement for reducing carbon emissions, but due to its low hydration activity and unstable working performance in the early stage, it is difficult to apply in 3D printed concrete (3DPC) as the main binder. In this study, a combination of ordinary Portland cement and calcium sulfoaluminate cement was used to activate GGBFS. In the presence of 0.2 wt% polycarboxylate superplasticizer (PCE), in order to achieve high-precision printing, hydroxypropyl methyl cellulose (HPMC) was used. The rheological properties of mortar were evaluated by the slugs-test and a rotational rheometer. The results show that the yield stress and thixotropy of slag cement-based 3D printing concrete are significantly increased, with addition of HPMC. The slugs-test shows its advantages in measuring rheological properties, such as superior repeatability of rheological data and a better association with 3D printing performance. Pumpability, extrudability, and buildability of the first printed layer of slag cement-based 3DPC were evaluated using pumping pressure, horizontal printing, and vertical printing. The results show that, with a 0.15 wt% HPMC, the 3D printing properties of the first layer are greatly improved, a stable and high-precision slag cement-based 3DPC can be developed, and the relationship between rheological properties and 3D printing performance can be established.

Effect of FDM printing patterns on mechanical properties of ABS

PurposeThe purpose of this study is to investigate how the amount of material used and printing parameters affect the mechanical and water sorption properties of acrylonitrile butadiene styrene printed parts.Design/methodology/approachThe specimens were printed using different printing parameters such as shell number, infill pattern and printing orientation, while accounting for the amount of material used. The mechanical properties of the printed parts were then evaluated using tensile, compression and flexural tests, along with sorption tests.FindingsThe results revealed that the maximum tensile stress of 31.41 MPa was obtained when using 100% infill and a horizontal printing orientation. Similarly, the maximum flexural strength and compression of 40.5 MPa and 100.7 MPa, respectively, were obtained with 100% infill. The printing orientation was found to have a greater impact on mechanical behavior compared to the number of shells or infill patterns. Specifically, the horizontal printing orientation resulted in specimens with at least 25% greater strength compared to the vertical printing orientation. Furthermore, the relationship between the amount of material used and strength was evident in the tensile and flexural tests, which showed a close correlation between the two.Originality/valueThis study’s originality lies in its focus on optimizing the amount of material used to achieve the best strength-to-mass ratio and negligible water infiltration. The findings showed that specimens with two shells and a 60% infill density exhibited the best strength-to-mass ratio.

Analisis Kekuatan Tarik dan Regangan Filamen Carbon Fiber Hasil 3D Print dengan Variasi Fill Density

Mechanical properties problems that are closely related to the strength of 3D printed products generally occur during the development of 3D printing machines, In which several components used are the results of additive manufacturing technology. The damages generally occur in the components that receive force and the damage is in the form of cracks and fractures. The focus of this study is to determine the effects of increasing the value of fill density on mechanical properties, especially tensile strength and strain with carbon fiber filament material. This study used an experimental method using two types of filament material: nylon carbon fiber and PLA carbon fiber with a diameter of 1.75 mm for each filament and a recommended printing temperature of 190-260°C. Both types of filaments were printed using a direct extruder type 3D printing machine with a build size of 180 mm x 180 mm x 180 mm and printing was carried out at atmospheric pressure and a horizontal printing area. The Universal Testing Machine carried out mechanical properties testing implementation related to tensile strength and strain. Based on the results of experiments and tests that have been carried out, the strain values ​​are 16.970 – 26.681% and the tensile strength is 19.244 – 23.899 MPa for nylon carbon fiber filament material. Whereas the PLA carbon fiber filament material, the strain value is 7.673 – 15.546%, and the tensile strength is 18.580 – 24.552 MPa. Therefore, based on the test results, it is known that the fill density parameter value has an influence on the strain value and tensile strength so that it can be used as a reference in setting machining parameters.

Light Distribution in 3D-Printed Thermoplastics.

Daylight distribution is an essential performance parameter for building facades that aim to maximize user comfort while maintaining energy efficiency. This study investigates the feasibility of using 3D-printed thermoplastic to improve daylight distribution and transmission. To identify how geometry influences light distribution and transmission, 12 samples with various patterns were robotically fabricated. In a physical simulation of spring, summer, and winter, a robotic arm was used to direct light onto the samples in both the vertical and horizontal print pattern directions. In addition, three samples of conventional facade materials, including a polycarbonate panel, a polycarbonate sheet, and a single sheet of glass, were compared with the 3D-printed samples. All samples were examined and compared using high dynamic range imaging to qualitatively characterize luminance. The data analysis demonstrated that 3D-printed geometry can successfully generate customizable diffusive light distribution based on the needs of the user. Furthermore, the results showed that the vertical pattern direction had higher light transmission values than the horizontal pattern direction.

Structural design and engineering of Striatus, an unreinforced 3D-concrete-printed masonry arch bridge

This paper describes the structural design and engineering of “Striatus”, a 3D-concrete-printed unreinforced masonry pedestrian bridge built in Venice in 2021 as part of the Time Space Existence exhibition organised by the European Cultural Centre. The project combines the latest developments in 3D concrete printing with the structural principles of historic unreinforced masonry. Typically, the structural applications of 3D concrete printing are limited to elements such as columns and walls loaded vertically, perpendicularly to the horizontal printing layers, to formwork elements or secondary structural elements. Indeed, fabrication constraints, delamination issues and the low tensile strength of the concrete have been seen as limiting factors to 3D concrete printing for structural applications demanding resistance to bending or predominant loading directions not perpendicular to the printing layers. By using unreinforced-masonry structural principles, this paper shows that structural elements spanning space horizontally, such as a pedestrian bridge, can be built by using the 3D concrete printing components as the main structure, working only in compression, loaded perpendicularly to the printed layers. Furthermore, as a compression-only structure following masonry principles, Striatus enabled the use of unreinforced concrete without any mechanical or chemical connections between the elements and the separation of concrete and steel, only used for the supports and to equilibrate the horizontal thrust of the arch effect through the tension ties. This work shows how the application of unreinforced masonry principles to 3D concrete printing offers new opportunities in terms of structural design and represents a strategy to increase sustainability by reducing material consumption and allowing reusability and recyclability of the structure. Finally, this paper discusses the critical aspects related to the design of Striatus from an engineering and construction point of view.

Effect of 3D Printing Process Parameters and Heat Treatment Conditions on the Mechanical Properties and Microstructure of PEEK Parts.

Fused deposition modeling (FDM) processed Poly-ether-ether-ketone (PEEK) materials are widely used in aerospace, automobile, biomedical, and electronics industries and other industries due to their excellent mechanical properties, thermal properties, chemical resistance, wear resistance, and biocompatibility, etc. However, the manufacture of PEEK materials and parts utilizing the FDM process faces the challenge of fine-tuning a list of process parameters and heat treatment conditions to reach the best-suiting mechanical properties and microstructures. It is non-trivial to make the selection only according to theoretical analysis while counting on a vast number of experiments is the general situation. Therefore, in this paper, the extrusion rate, filling angle, and printing orientation are investigated to adjust the mechanical properties of 3D-printed PEEK parts; then, a variety of heat treatment conditions were applied to tune the crystallinity and strength. The results show that the best mechanical performance is achieved at 1.0 times the extrusion rate, varied angle cross-fillings with ±10° intervals, and vertical printing. Horizontal printing performs better with reduced warpage. Additionally, both crystallinity and mechanical properties are significantly improved after heat treatment, and the best state is achieved after holding at 300 °C for 2 h. The resulting tensile strength is close to 80% of the strength of injection-molded PEEK parts.

Influence of printing conditions on the mechanical properties of copper-polylactic acid composites obtained by 3D printing fused deposition modelling

The main goal of the present study was to investigate the tensile properties of a commercially available copper-PLA filament, 3D printed using the fused deposition modeling technique. In this aim, different printing parameters were varied, such as printing orientation, fill pattern and infill density. Tensile testing of 3D printed samples has been performed conventionally, according to the ISO 527 standard, to evaluate the influence of the manufacturing parameters on the mechanical properties of the printed parts. The results suggest that a horizontal printing orientation produces stronger parts compared to the vertical printing, for the investigated material, mainly due to the occurrence of a different fracture mechanism. Additionally, a linear fill pattern, combined with a higher infill density results in superior mechanical strength.

3D printing of silica-based ceramic cores reinforced by alumina with controlled anisotropy

Ceramic core (CC) is a key component in the casting of aero-engine turbine blades, and CC through 3D printing is crucial to the growing aviation technology. However, these silica CCs are highly limited by their high temperature softening and inevitable anisotropy. In this work, silica-based CCs reinforced by alumina powders are manufactured by 3D printing via digital light processing (DLP) stereolithography, and the anisotropy in microstructure and property was investigated. In the CC without alumina powders, multilayer structures with significant interlayer gaps are exhibited in horizontal printing direction suggesting significant anisotropy in microstructure, which is related to the particle deposition in printing. As the alumina content is 6 wt%, microstructures become uniform, due to the enhanced particle rearrangement between different layers. To assess the mechanical anisotropy, the ratio of vertical strength to horizontal strength (σV/σH) is raised, and the σV/σH ratios rise from 0.45 to 0.86 at room temperature and 0.52–0.89 at 1540 °C with increasing alumina content from 0 to 6 wt%. As the alumina content is 6 wt%, the CC exhibits high temperature flexure strengths as high as 17.9 MPa and 19.5 MPa in different directions, well satisfying the demands for turbine blades casting. This article inspires a profound understanding on the anisotropy control in 3D printing of CC with excellent high-temperature mechanical properties.

Anisotropy management on microstructure and mechanical property in 3D printing of silica-based ceramic cores

Ceramic core is an essential component in the precise casting of hollow turbine blades, and the investigation on 3D printing of silica-based ceramic cores is crucial to the development of aviation industry; however, they are suffered from difficulty in high-temperature strength and structural anisotropy. In present work, silica-based ceramic cores were prepared via DLP stereolithography 3D printing, and the anisotropy management on microstructures and properties were explored based on the particle size of fused silica powders. In 3D printed ceramic cores with coarse powders, significant anisotropy was displayed exhibiting multilayer structure with large gaps in horizontal printing and uniform porous microstructure in the vertical direction, which was further explained by the particle deposition in printing. With finer silica powders, the uniformity in the microstructures was highly improved, attributed to the enhanced particle dispersion in ceramic slurries and promoted interlayer particle rearrangement during sintering. To evaluate the anisotropy in mechanical property, the ratio of vertical strength to horizontal strength (σV/σH) was proposed, which rose from 0.48 to 0.86 as the particle size decreased from 35 µm to 5 µm, suggesting enhanced mechanical uniformity. While the average particle size of silica powders was 5 µm, the flexure strengths of ceramic cores in different directions were up to 18.5 MPa and 16.3 MPa at 1540 °C with σV/σH ratio of 0.88, which well satisfied the demands for the casting of turbine blades. This work inspires new guidance on the anisotropy management in ceramic cores prepared by 3D printing, and provides new technology for fabrication of silica-based ceramic cores with superior high temperature mechanical properties.

A pilot study on three-dimensional printing of stainless steel arch bars for orthognathic segmental jaw surgeries

IntroductionThe fabrication process of an arch bar used during a corrective jaw surgery is traditionally labour intensive and time consuming when done manually by a dental technician. The objectives of this study are therefore to test the feasibility of using selective laser melting (SLM) to directly print patient-specific stainless steel (SS316L) arch bars from computer-aided-design (CAD) files and investigate the most optimal printing parameters to achieve that. Material and methodsAn initial print-out of 72 SS316L test coupons was done to determine the most optimal print orientation and print bed location based on chemical composition and mechanical test results from 4 different printer settings:Parameter 1: 200 W, 50 µmParameter 2: 150 W, 50 µmParameter 3: 200 W, 30 µmParameter 4: 150 W, 30 µmTen archived digital lower dentition scans were then used to produce 10 CAD files for 3D printing of 280 dental arch bars using the aforementioned parameters. All 3D printed arch bars were then assessed for fit and subjected to physical testing. ResultsTest coupons printed using parameter 4 in the horizontal print bed (0°) location had the best mechanical properties. Similarly, for 3D printed arch bars, those printed using parameter 4 had the highest proportion of arch bars with satisfactory fit. The most common area of distortion is the posterior molar region. Conclusion3D printing of SS316L dental arch bars is feasible via a digital workflow using low laser power (150 W) and low layer thickness (30 µm) in a Renishaw AM 400 printer (from Renishaw plc, Gloucestershire).

Dream interpretation and parodies of translation in Aḥmad Fāris al-Shidyāq’s al-Sāq ʿalā al-sāq

ABSTRACT In Aḥmad Fāris al-Shidyāq’s 1855 semiautobiographical picaresque al-Sāq ʿalā al-sāq (Leg Over Leg), the author’s double, the Fāriyāq, holds a series of jobs that parodically stand in for al-Shidyāq’s own employments. This article addresses the Fāriyāq’s career as an oneiromancer, reading it as an allegory of al-Shidyāq’s work as a Bible translator for European Protestant missionaries. By representing the muʿarrib (translator into Arabic) as the muʿabbir (dream interpreter), I argue, al-Shidyāq places the translator in a genealogy of professional interpreters, inheriting the tradition of early-modern Ottoman court interpreters who wielded the power of expertise against the social and economic power of their patrons. At a moment of historical shift from circuits of scribal patronage to a more horizontal print market, al-Shidyāq removes the oneiromantic tradition from its hierarchical patron economy and parodically reinscribes it in an emergent print culture, initiating an anonymous yet intimate community of laughter.

Slanted and cluttered: Solving deficiencies in SLM-manufactured lattice geometries

The rapid growth of the geriatric population in industrial societies is expected to increase the demand for prosthetic implants. Unfortunately, current products exhibit shortcomings such as inadequate sizing or excessive material strength both of which hamper the recovery of fractures. Selective laser melting (SLM), as a manufacturing method, is highly suited for optimizing the geometry and topology of products. However, SLM however, seems to restrict the manufacturing precision to mostly horizontal printing which is inefficient when considering the build envelope. Additionally, certain elongated geometries are subject to warpage when printed horizontally. To address these issues, our study investigated the feasibility of vertically oriented porous structures using SLM. It will report on two specific deficiencies, namely slanting and cluttering, that were revealed through X-ray computer tomography. To facilitate the manufacturing of slender, porous structures, the paper will offer and examine heuristics that minimize the defects. The preliminary results indicate that structures such as shell reinforcements and bio-inspired unit cells reduce the occurrence of slanting and cluttering and might serve as interim solutions for the printing of large filigree structures. The general findings suggest that more dedicated research is necessary to understand the relationship between geometrical features and manufacturing precision in SLM.

CAD-CAM complete denture resins: an evaluation of biocompatibility, mechanical properties, and surface characteristics

ObjectivesThis study evaluated the biocompatibility, mechanical properties, and surface roughness of CAD-CAM milled and rapidly-prototyped/3D-printed resins used for manufacturing complete dentures. MethodsSix groups of resin specimens were prepared, milled-base (MB), milled-tooth shade (MT), printed-tooth shade (PT), printed-base with manufacturer-recommended 3D-printer (PB1), printed-base with third-party 3D-printer (PB2), printed-base in a vertical orientation (PB2V). Human epithelial (A-431) and gingival (HGF-1) cells were cultured and tested for biocompatibility using Resazurin assays. Three-point bending and nanoindentation tests measured the mechanical properties of the resin groups. Surface roughness was evaluated using a high-resolution laser profilometer. ANOVA and post-hoc tests were used for statistical analyses (α = 0.05). Results: There were no significant differences in biocompatibility between any of the investigated groups. MB revealed a higher ultimate strength (p = 0.008), elastic modulus (p = 0.002), and toughness (p = 0.014) than PB1. MT had significantly higher elastic modulus than PT (p < 0.001). Rapidly-prototyped resin samples with a manufacturer-recommended 3D-printer (PB1) demonstrated higher ultimate strength (p = 0.008), elastic modulus (p < 0.001), hardness (p < 0.001) and a reduced surface roughness (p < 0.05) when compared with rapidly-prototyped groups using a third-party 3D-printer (PB2). Rapidly-prototyped samples manufactured with a vertical printing orientation (PB2V) revealed a significantly lower elastic modulus than samples groups manufactured using horizontal printing orientation (PB2) (p = 0.011). Conclusions: Within the limits of this present study, CAD-CAM milled and rapidly-prototyped complete denture resins performed similarly in terms of biocompatibility and surface roughness. However, the milled denture resins were superior to the rapidly-prototyped denture resins with regard to their mechanical properties. Printing orientation and type of 3D-printer can affect the resin strength and surface roughness.

Influence of additive manufacturing by laser powder bed fusion on the susceptibility of Alloy 718 to hydrogen embrittlement

ABSTRACT The susceptibility of additively manufactured (AM) and heat-treated Alloy 718 to hydrogen embrittlement was compared to that of wrought Alloy 718. Specimens were prepared from laser powder bed fusion (LPBF) coupons built with the long axis in the x-direction (horizontal printing) and with the long axis in the z-direction (vertical printing). Despite the heat treatment, coupons printed horizontally demonstrated retained elongated grains parallel to the build, z-direction, while the coupons printed vertically had a relatively uniform and small grain structure perpendicular to the build direction, but a highly elongated grain structure parallel to the build direction. Slow strain rate testing under standardised cathodic charging conditions in 0.1 M H2SO4 indicated a greater susceptibility to hydrogen embrittlement of the test specimens manufactured from coupons printed horizontally, attributed to cracks more readily propagating along the elongated direction of the microstructure.

Characterization of 3D-printed bolus produced at different printing parameters

We aimed to analyze the effects of printing parameters on characterization of three-dimensional (3D) printed bolus used in external beam radiotherapy. Two sets of measurements were performed to investigate the dosimetric and physical characterization of 3D-printed bolus at different printing parameters. In the first step, boluses were produced at different infill-percentages, infill-patterns and printing directions. Two-dimensional (2D) dose measurements were performed in Elekta Versa HD linear accelerator using 6 MV photon energy. Measured 2D dose maps for both printed and reference bolus materials were compared using the 2D gamma analysis method. Additionally, patient-specific bolus was produced with defined optimum printing parameters for anthropomorphic head and neck phantom. Then, point dose measurements were performed to evaluate the feasibility of printed bolus in clinical use. In the second step, physical measurements were carried out to evaluate the printing accuracy, the mean hounsfield unit (HU) value and the weight of 3D-printed boluses. According to our measurement, infill-percentage, infill-pattern and printing direction significantly changed the dosimetric and physical properties of the 3D-printed bolus independently. Maximum gamma passing rate at 1.5 and 5 cm depths were found as 93.8% and 98.8%, respectively, for 60% infill-percentage, sunglass fill infill-pattern and horizontal printing direction. The printing accuracy of the products was within 0.4 mm. Dosimetric and physical properties of the printed bolus material changed significantly with the selected printing parameters. Therefore, it is important to note that each combination of these printing parameters that will be used in the production of patient-specific bolus should be investigated separately.

Effect of different support angles on the fitness of removable partial denture framework fabricated using selective laser melting technique

Objective: To evaluate the fitness of bilateral free-end dentition defect removable partial denture framework fabricated by selective laser melting (SLM) technique with different support angles. Methods: After the control group has been set to eliminate the system error, and according to the standard model of bilateral mandibular posterior teeth loss, eighteen titanium alloy removable partial denture frameworks fabricated by SLM technology were divided into 3 groups with support angles of 0° (horizontal group), 45°(45° group) and 90° (vertical group). Plaster cast with duplicated structure of tissue surface of the removable partial denture (RPD) framework was obtained. A three-dimensional scanner was used to scan original and duplicated plaster casts. The gaps between framework and the model in different parts were analyzed using Geomagic Qualify software to evaluate the fitness of the framework with visual method. Results: The framework fits on the plaster model completely, and its tissue surface fitted on the plaster model well. The deviation between frameworks and plaster casts was calculated as follow: the total deviations of the horizontal, 45°, and vertical group were (0.146±0.017), (0.182±0.015) and (0.185±0.022) mm respectively. The mean deviation of the horizontal group was significantly less than those of the 45° group and the vertical group (P<0.05). Moreover, there was no significant difference in the total deviation between the 45° group and the vertical group. The total deviation of occlusal rest of the horizontal group was significantly less than that of the 45° group (P<0.05). However, no significant difference was detected in the deviation of occlusal rest among the vertical group, the horizontal group, and the 45° group (P>0.05). There was no significant difference in the deviation of occlusal rest among the vertical group, the horizontal group, and the 45° group. The deviation of clasp of the horizontal group was significantly smaller than those of the 45° group and the vertical group (P<0.05). Whereas, there was no significant difference in the deviation of clasp between the 45° group and the 90° group (P>0.05). No significant difference was found in the deviation of lingual bar among the three groups (P>0.05). Conclusions: Among the three kinds of bilateral free-end dentition defect RPD framework fabricated by SLM in different support angles, horizontal printing was proved to reach the minimal deviation, even though the fitness of all three kinds of frameworks can fullfil clinical requirements according to previous studies.

Conformal additive manufacturing using a direct-print process

In conventional additive manufacturing, most processes for creating the layers of a part are performed on a horizontal plane. In contrast, a conformal additive manufacturing process has been suggested in order to build a real 3D structure on a freeform surface using a direct-print process based on material extrusion. A new algorithm was developed that is able to use the standard 3D printing file format that includes both a 3D model to be printed and a 3D model of a freeform substrate along with the desired printing parameters as input, and it returns G-code instructions for the 3D printing process as output. A slicing surface was generated to slice the 3D model by offsetting the surface of a freeform substrate model by a discrete amount (i.e., layer thickness) for each layer. The perimeters of each layer (including the internal features) were extracted based on the intersections between the slicing surface and the 3D model, and infill toolpaths were created by projecting 2D patterns reflecting the features to be printed with a desired fill factor (in the x–y plane) onto the slicing surface to create 3D patterns. Two printing methods, complete conformal printing and a hybrid methodology that combines conformal printing with conventional horizontal printing, were presented. Several 3D models were sliced and printed on a freeform surface to validate the developed algorithm.