Earticle

This study examines the effects of additive manufacturing (AM) orientations and support structures on the compressive strength of lattice structures. Test specimens were fabricated using a selective laser melting (SLM) process with AlSi10Mg material under three conditions: horizontally aligned (0°), tilted at 45°, and supported. Compression tests were conducted using a universal testing machine (UTM) and Digital Image Correlation (DIC) to evaluate mechanical behavior. The results showed that the supported horizontal specimens exhibited the highest compressive strength, while the 45° tilted specimens had the lowest due to interlayer separation and localized failures. The findings highlight the significance of build orientation and support design in optimizing AM lattice structures. Future research should explore various lattice configurations, material selections, and post-processing effects to further enhance structural performance.

In this paper, the CFRP(Carbon Fiber Reinforced Plastic) parts were printed and cut in a large-scale additive and subtractive hybrid manufacturing system. A method to increase the strength and durability of a product by identifying the interlayer adhesion during the printing process of a large-scale additive manufacturing hybrid system was investigated. According to the printing conditions(CF content, deposition temperature, compaction process), the specimen was printed and cut to determine the tensile strength in the printing direction. As a result of the experiment, the highest tensile strength was shown when ABS-CF 20wt.% Compound was printed at 230℃ extrusion temperature, and the higher the CF content of the material, the lower the tensile strength. As a result of observing the inside of the test piece through an optical microscope, a large number of voids were kept inside the test piece. To remove voids generated inside the test piece, a compaction process was applied to the additive manufacturing hybrid system to prepare a test piece. As a result, void size decreased, and the strength of the part showed a tendency to increase. It is thought that additive manufacturing with high tensile strength can be obtained through studies on the optimization of deposition conditions in additive manufacturing hybrid systems.

We attempted to provide an overview of the laws and current state of the 3D printing industry in South Korea and around the world, using the annual industry surveys and the Wohler report. Additionally, we reviewed articles relating to the potential exposure to hazards associated with 3D printing using metal materials. In South Korea, there were 406 3D printing-related businesses, employing 2,365 workers, and the market size was estimated at 455.9 billion won in 2021. Globally, the average growth rate of the 3D printing industry market over the past 10 years was 27.4%, and the market size was estimated at $11.8 billion in 2019. The United States had the highest cumulative installation ratio of industrial 3D printers, followed by China, Japan, Germany, and South Korea. A total of 6,168 patents related to 3D printing were registered in the US between 2010 and 2019. Harmful factors during metal 3D printing was mainly evaluated in the powder bed fusion and direct energy deposition printing types, and there is a case of material extrusion type with metal additive filaments. The number, mass, size distribution, and chemical composition of particles were mainly evaluated. Particle concentration increases during the opening of the chamber or post-processing. However, operating the 3D printer in a ventilated chamber can reduce particle concentration to the background level. In order to have a safe and healthy environment for 3D printing, it is necessary to accumulate and apply knowledge through various studies.

This study was conducted to compare the mechanical properties of NAB (Ni-Al-Bronze) material manufactured using WAAM (wire arc additive manufacturing) technology and cast NAB that has been used. Two types of mechanical property test pieces were collected from the deposited bulk NAB material according to the direction of deposition, and compared with each other. As a result of mechanical property evaluation, the deposited NAB exhibited anisotropy according to the direction of deposition, and showed high tensile strength, hardness, and shock absorption in the longitudinal direction of the welding line.

Additive manufacturing is a new approach to design and production. This applies in particular to processes such as repair and rework of selected components. Additive manufacturing can produce almost any shape, and from an MRO part perspective, additive manufacturing offers tremendous advantages. The special feature of additive manufacturing is that it is particularly economical for small-volume production as the number of units is irrelevant compared to the existing manufacturing process. The purpose of this study was started from the MRO point of view, and it Identify changes and respond to the Blisk It is a study on the effect of changing the conditions on the path of the toolpath and the CAM during additive manufacturing using CAM after finding suitable conditions. metal powder.The metal powder withstands various corrosive environments and age hardening occurs very slowly. Inconel 718, which can be used in various applications such as nuclear facility-related parts, aerospace, oil facilities, turbines, and valves, was used. This is SUS 316L with good high temperature strength. The variable of the laser used in the study is the laser power, and the variables on the CAM are Operation, Stepover, Pattern, etc. In the relation between laser power and feed, when feed is specified as 500mm/min, laser power of 700W was most suitable. As for the conditions on NX CAM, ADDITIVE PROFILE Stepover was 0.8mm for Operation, and Infills and Finish for Pattern. When stacking, each layer should be overlapped with the result. Therefore, the stepover should be smaller than the laser spot size and reprocessing should be done in terms of repair, so infills and finish were applied to work larger than the actual product shape.

Purpose: The purpose of this study is to analyze the fitness of heat - pressed ceramic laminate veneers fabricated using the additive manufacturing. Methods: Impression was replicated by using light body silicone and heavy body silicone on the custom tray, and it was fabricated using Type Ⅳ Stone. The test specimens were prepared by using a dental scanner, a laminating veneer using a dental design program, and a specimen with a 3D printer . The control specimens were prepared by the lost wax technique and heat - pressed to fabricate the specimens. The data of the specimens were measured by the RMS value of the internal fitness a using a 3-dimensional measurement program. Results: The Stereolithography laminate veneer group was measured at 78.10(4.09) μm and the LWV group was measured at 31.50(5.10) μm. There is a significant difference between the two groups (p<0.001) Conclusion : Evaluation of fitness laminate veneers was fabricated by additive manufacturing showed the difference statistically significantly and clinically acceptable result.

Purpose: This study aimed to evaluate the fit of the anterior and posterior teeth printed using two light-curing three-dimensional (3D) printers. Methods: Anterior and posterior single crowns were designed using dental software and were printed using 2 types of 3D printers, liquid crystal display (LCD) and digital light processing (DLP) (n=40). After the printed crown was scanned again from inside and outside, the prepared teeth were evaluated using a 3D program. To compare the root mean square (RMS) results among groups (α=0.05), the one-way analysis of variance and Tukey‘s test were used. Results: No statistically significant difference was found between the mean RMS values of the anterior and posterior teeth (p>0.05). However, as a result of comparing the internal, external, and tooth shapes, the DLP group showed significantly low errors in the inner and outer surfaces than LCD group (p<0.05). Conclusion: In terms of clinical acceptance standard of 100 μm, the fit of the anterior and posterior teeth fabricated using LCD and DLP was clinically acceptable.

Purpose: The purpose of this study was to assess the fitness of anterior and posterior interim crowns fabricated by three different additive manufacturing technologies. Methods: The working model was digitized, and single crowns (maxillary right central incisor and maxillary right first molar) were designed using computer-aided design software (DentalCad 2.2; exocad). On each abutment, interim crowns (n=60) were fabricated using three types of additive manufacturing technologies. Then, the abutment appearance and internal scan data of the interim crown was obtained using an intraoral scanner. The fitness of the interim crowns were evaluated by using the superimposition of the three-dimensional scan data (Geomagic Control X; 3D Systems). The one-way analysis of variance and Tukey posterior test were used to compare the results among groups (α=0.05). Results: A significant difference was found in the fitness of the interim crowns according to the type of additive manufacturing technology (p<0.05). The posterior interim crown showed smaller root mean square value than the anterior interim crown. Conclusion: Since the fitness of the posterior interim crown produced by three types of additive manufacturing technology were all within clinically acceptable range (<120 μm), it can be sufficiently used for the fabrication of interim crowns.

Purpose: The goal of this study was to determine the clinical acceptability of various cement space settings for the marginal and internal fit of a zirconia core manufactured using additive manufacturing. Methods: The maxillary right incisor served as the master model. After scanning the maxillary right incisor with a dental 3D (three-dimensional) scanner, the stereo lithography file was created using different cement space settings of 40, 120, and 200 μm using computer- aided design software (Dental System 2018; 3Shape). The marginal and internal fit of the 3 groups were determined using the silicon replica technique. Measurement points were divided into the following three categories: margin, axial wall, and incisal. To ensure more accurate measurements, these three measurement points were divided into 8 points. The Shapiro-Wilk, one-way ANOVA, and Tukey’s honestly significant difference test (for all tests α=0.05) were the statistical analyses that were included in the study. Results: The CS (cement space)-200 group had better marginal and internal fit than the CS-40 and CS-120 groups, and there were statistically significant differences at the marginal and incisal points, except for the axial wall points. CS-200 group, both marginal and internal fit were within 120 μm, which is the clinically acceptable value. Conclusion: This study suggests that a 200 μm cement space setting is ideal for optimal marginal and internal fit of 3D-printed ceramic crowns.

Purpose: The purpose of this study was to evaluate the clinical acceptability of the marginal and internal gap of Co-Cr metal copings fabricated with stereolithography (SLA). Methods: Titanium master dies were milled after scanning of the prepared tooth (n=30). For group I, Co-Cr metal copings were made from conventional lost-wax technique(LWT, n=10). For group II, the master dies were scanned and designed with CAD system. Then, metal copings were milled with Co-Cr(SUB, n=10). For group III(ADD, n=10), the scanning and design procedures were same as group II and burn-out resins were fabricated with SLA device. The marginal and internal discrepancies were measured under an optical microscope(100x) on ten reference points and were statistically analyzed with one-way ANOVA(α=.05). Results: The mean total discrepancies were 53.76±12.42μm in the LWT group and 69.82±15.48μm in the ADD group. The SUB group showed the largest total mean value 110.33±13.77μm. There was statistically significant difference between the SUB and the other groups(P<0.05). Conclusion : Co-Cr metal copings fabricated with SLA technology showed clinically acceptable value on marginal and internal gap and there was no statistically significant difference between conventional lost-wax technique and SLA.

Purpose: This study aimed to evaluate and compare the marginal and internal fit of provisional dental prostheses fabricated using two different printing techniques with identical computer-aided design data and design parameters, as well as to assess their clinical applicability. Methods: A three-unit fixed dental prosthesis was designed using the maxillary right first premolar and first molar as abutments, with the missing right second premolar serving as a pontic. Based on the design, a negative mold was fabricated using silicone impression material, and dental stone was poured to create working models. Each model was scanned using a dental scanner, and a total of 20 specimens (10 per group) were fabricated from the resulting STL data. The fit of the specimens was assessed using the silicone replica technique and examined under an optical microscope at 12 measurement points, including the marginal area, axial wall, and occlusal surface. Statistical analysis was performed using an independent sample t-test (α=0.05). Results: Prostheses fabricated using the liquid crystal display (LCD) method demonstrated significantly smaller gap values at all measured sites compared with those produced using the digital light processing method (p<0.05). Although most gap measurements in both groups remained within the clinically acceptable limit of 120 μm, the LCD-fabricated restorations consistently demonstrated superior overall adaptation. Conclusion: The findings of this study indicate that the type of printing method significantly affects the fit of provisional restorations. For improved restoration accuracy, the use of the LCD printing method is recommended.

In material extrusion additive manufacturing, extrusion throughput and bead shape are key factors affecting deposition quality and productivity. This study investigated the effects of melt index (MI) and glass fiber (GF) reinforcement on the extrusion behavior of HDPE-based materials. Three neat HDPE materials and two HDPE+GF composites with different MI values were extruded under identical conditions, and their extrusion throughput, bead thickness, and shape stability were evaluated. The results showed that the average extrusion throughput increased with increasing MI, whereas bead thickness decreased. The HDPE+GF composites exhibited better shape stability than neat HDPE; however, brittle fracture behavior was observed under bending deformation. These findings suggest that the extrusion throughput, bead shape, and shape stability of HDPE-based materials should be evaluated in advance according to MI and GF reinforcement before applying them to material extrusion additive manufacturing.

현대 주조산업에서는 적층제조기술과 같은 신기술을 도입하면서 과거에는 불가능했던 일들의 실현가능성을 보여 주고 있다. 이미 해외에서는 적층제조기술을 활용한 중자 생산 및 적용 사례가 심심치 않게 보도되고 있으며, 정부지원 하에 고유 기술들을 개발하고 시장을 확장해 나가고 있다. 반면 국내에서는 고유장비 기술은커녕 적층제조기술의 활용조 차 전무한 실정이다. 이러한 상황에서 적층제조기술의 도입과 국산화는 반드시 필요하다. 본 논문의 각 장에서는 여러 가지 적층제조기술 중 접착제 분사 기술에 관련된 적층제조장비의 개발 과정에서부터 개발 장비를 활용한 산업용 중자 생산의 내용을 다루고 있으며, 실제 주조 산업의 적용 가능성에 대해서 언급하고 있다.

In recent years, new technologies such as additive manufacturing have been applied to casting industry, paving new ways to achieve what have traditionally been impossible. In the global market, numerous successful cases of producing cores using additive manufacturing technology have been reported, and new techniques and markets are being developed under governments’ support. In Korea, however; cases of applying additive manufacturing to casting are hard to come by, not to mention domestic AM machines and related technologies. Under these circumstances, introduction of additive manufacturing technologies and customized application to domestic casting industry are required. Each chapter of this paper explores topics ranging from the development of AM machine using binder jetting technology among various AM techniques through producing industrial cores to the on-site applications in the foundries.

기존의 주조 방식은 긴 제작 시간과 많은 비용이 소모되며, 즉각적인 디자인 수정이 불가능하여 다변화하는 현대 사회에 대응하기 어려웠다. 때문에 주조 산업은 새로운 대안이 필요했으며 그 중 하나가 적층 제조 기술과의 접목이다. 적층제조기술에는 7가지가 있으나 본 논문에서는 PBF를 활용한 중자 제작을 살펴보려고 한다. 현재의 적층 제조 기술 장비들은 대부분 외산 장비들로 기능 활용과 서비스의 제약이 따르고 있어서 장비의 국산화가 필요하였고 장비의 개발과 함께 기술 활용의 내용을 담았다. 각 장에서는 PBF의 장비 개발 단계 및 소재 적용과 변수 설정에 대해서 서술하고 있으 며, 최종적으로 기술을 활용한 산업용 중자 개발의 성공과 특성에 대한 정보를 보여주고 있다.

Traditional casting methods require long production lead time and high cost while not accommodating design changes easily. One of the technological alternatives to improve casting method to meet diversifying needs is Additive Manufacturing (AM). Among the 7 AM techniques, Powder Bed Fusion (PBF) is deemed most appropriate for casting applications. Currently, most AM machines are imported; therefore limiting the scope of available services and applications. This paper explores the domestic development of AM machines as well as the applications in casting. Each chapter describes development phases of PBF machines, applicable materials and parameter settings, while the last chapter illustrates a successful case of additive manufacturing industrial casting cores.

A three-dimensional physical part can be fabricated from a three-dimensional digital model in a layer-wise manner via additive manufacturing (AM) technology, which is different from the conventional subtractive manufacturing technology. Numerous studies have been conducted to take advantage of the AM opportunities to penetrate bespoke custom product markets, functional engineering part markets, volatile low-volume markets, and spare part markets. Nevertheless, materials issues, machines issues, product issues, and qualification/certification issues still prevent the AM technology from being extensively adopted in industries. The present study briefly reviews the standard classification, technological structures, industrial applications, technological advances, and qualification/certification activities of the AM technology. The economics, productivity, quality, and reliability of the AM technology should be further improved to pass through the technology adoption lifecycle of innovation technology. The AM technology is continuously evolving through the introduction of PM materials, hybridization of AM and conventional manufacturing technologies, adoption of process diagnostics and control systems, and enhanced standardization of the whole lifecycle qualification and certification methodology.

Additive manufacturing (AM) is defined as the manufacture of three-dimensional tangible products by additively consolidating two-dimensional patterns layer by layer. In this review, we introduce four fundamental conceptual pillars that support AM technology: the bottom-up manufacturing factor, computer-aided manufacturing factor, distributed manufacturing factor, and eliminated manufacturing factor. All the conceptual factors work together; however, business strategy and technology optimization will vary according to the main factor that we emphasize. In parallel to the manufacturing paradigm shift toward mass personalization, manufacturing industrial ecology evolves to achieve competitiveness in economics of scope. AM technology is indeed a potent candidate manufacturing technology for satisfying volatile and customized markets. From the viewpoint of the innovation technology adoption cycle, various pros and cons of AM technology themselves prove that it is an innovative technology, in particular a disruptive innovation in manufacturing technology, as powder technology was when ingot metallurgy was dominant. Chasms related to the AM technology adoption cycle and efforts to cross the chasms are considered.

Additive manufacturing (AM) is defined as the manufacture of three-dimensional tangible products by additively consolidating two-dimensional patterns layer by layer. In this review, we introduce four fundamental conceptual pillars that support AM technology: the bottom-up manufacturing factor, computer-aided manufacturing factor, distributed manufacturing factor, and eliminated manufacturing factor. All the conceptual factors work together; however, business strategy and technology optimization will vary according to the main factor that we emphasize. In parallel to the manufacturing paradigm shift toward mass personalization, manufacturing industrial ecology evolves to achieve competitiveness in economics of scope. AM technology is indeed a potent candidate manufacturing technology for satisfying volatile and customized markets. From the viewpoint of the innovation technology adoption cycle, various pros and cons of AM technology themselves prove that it is an innovative technology, in particular a disruptive innovation in manufacturing technology, as powder technology was when ingot metallurgy was dominant. Chasms related to the AM technology adoption cycle and efforts to cross the chasms are considered.

PURPOSE. To evaluate the fit of a three-unit metal framework of fixed dental prostheses made by subtractive and additive manufacturing. MATERIALS AND METHODS. One master model of metal was fabricated. Twenty silicone impressions were made on the master die, working die of 10 poured with Type 4 stone, and working die of 10 made of scannable stone. Ten three-unit wax frameworks were fabricated by wax-up from Type IV working die. Stereolithography files of 10 three-unit frameworks were obtained using a model scanner and three-dimensional design software on a scannable working die. The three-unit wax framework was fabricated using subtractive manufacturing (SM) by applying the prepared stereolithography file, and the resin framework was fabricated by additive manufacturing (AM); both used metal alloy castings for metal frameworks. Marginal and internal gap were measured using silicone replica technique and digital microscope. Measurement data were analyzed by Kruskal-Wallis H test and Mann-Whitney U-test (${\alpha}=.05$). RESULTS. The lowest and highest gaps between premolar and molar margins were in the SM group and the AM group, respectively. There was a statistically significant difference in the marginal gap among the 3 groups (P<.001). In the marginal area where pontic was present, the largest gap was $149.39{\pm}42.30{\mu}m$ in the AM group, and the lowest gap was $24.40{\pm}11.92{\mu}m$ in the SM group. CONCLUSION. Three-unit metal frameworks made by subtractive manufacturing are clinically applicable. However, additive manufacturing requires more research to be applied clinically.