Microlattice is well known as an efficient structure having a low density which maintains mechanical properties, so microlattice is being applied to the structural design of lightweight material in many industrial fields. In this study, we proposed a core-shell microlattice structure by the conformal coating of a metal nanoparticle-polymer composite in order to enhance the mechanical properties of polymeric microlattice printed by light-based 3D printing method. Polymeric architected microlattice was fabricated using digital light printing, which enabled the printing of complex structures with good surface smoothness. Then, the polymeric microlattice was conformally coated with aluminum nanoparticle-polymer composites. To investigate the effect of the metal nanoparticle-polymer composite coating on the mechanical properties of the microlattice, we studied the compressive behavior of cubic and octet-truss microlattices. As a result, we confirmed that both compressive strength and toughness of the two types of microlattices were effectively increased by coating with aluminum nanoparticle-polymer composites.
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Robust catalyst 3D microarchitectures by digital light printing with ceramic particle–polymer composites Do Hyeog Kim, Sang-Hoon Nam, Gina Han, Seo Rim Park, Gwang Ho Jeong, Seok Kim, Young Tae Cho, Nicholas Xuanlai Fang APL Materials.2024;[Epub] CrossRef
Study on Mechanical Properties of MWCNT Reinforced Photocurable Urethane Acrylate for Additive Manufacturing Hyunjun Jo, Bum-Joo Lee Journal of the Korean Society for Precision Engineering.2024; 41(3): 199. CrossRef
Nature-inspired architected materials have been widely used to achieve efficient structural materials by harnessing their cellular and hierarchical structures. For example, biological materials observed in bone, shell, nacre, and wood contain constituents, ranging from nanometers to centimeters, arranged in an ordered hierarchy. Because of their composited structures that contain micro and nanoscale building blocks arranged in an ordered hierarchy and the material size effect in the mechanical strength of nano-sized solids, bioceramic materials are mechanically robust and lightweight. The design principles offered by hard biological materials of multiscale composite structures can assist in the creation of advanced ceramic architectures. In addition, the evolution of additive manufacturing technologies has enabled the fabrication of materials with intricate cellular architected materials. In this review, we discussed advanced additive manufacturing for the fabrication of nature-inspired multiscale ceramic structures by combining conformal thin-film coating technique with conventional additive manufacturing methods.
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SEM Image Quality Improvement and MTF Measurement Technique for Image Quality Evaluation Using Convolutional Neural Network Chan Ki Kim, Eung Chang Lee, Joong Bae Kim, Jinsung Rho Journal of the Korean Society for Precision Engineering.2023; 40(4): 275. CrossRef
Recently, competition in the manufacturing industry related to the preoccupation of new markets has drastically changed due to the increase in small quantity batch production products. Besides, business models utilizing 3D printing technology suitable for flexible manufacturing are gaining interest. As 3D printing technology is becoming more common, Design for Additive Manufacturing is also in the spotlight. However, the productivity of 3D printing technology is still insufficient in terms of mass production. In this study, the possibility of innovation in mass production process that combines 3D printing technology is presented through the case of innovation in manufacturing productivity of medium-speed engine cylinder head through the integration of sand 3D printing technology. It outlines how sand 3D printing technology is applied to cylinder head mass production processes, how the quality of cylinder head products can be improved compared to conventional pattern-based molding methods, and how productivity can be maximized by reducing process time and human error through hybrid production method with sand 3D printed integrated design cores. In conclusion, this paper presents the effectiveness of sand 3D printing technology which can secure product competitiveness by increasing the production capacity of mass production process, reducing production costs, improving quality, and reducing loss.
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Digital Transformation of Metal Casting Process Using Sand 3D Printing Technology with a Novel Methodology of Casting Design Inside a Core Kuk-Hyun Han, Jin-Wook Baek, Tae Wan Lim, Ju Min Park International Journal of Metalcasting.2023; 17(4): 2674. CrossRef
Microchannel-based chemical reactor is widely used to develop chemical products. High-efficiency reactors are required to produce high-quality chemical products. The reaction efficiency is highly related to the mixing ratio. In this paper, an inner structure model in the reactor was designed to improve the mixing ratio. Computational fluid dynamic (CFD) analysis was carried out for two-phase flow in a continuous flow reactor using a commercial software. A case model of the different inner structures was designed to evaluate the mixing rate. Velocity profiles, mixing ratio, and pressure fields of each model were obtained by two-fluid flow analysis using CFD. Based on the analysis results, a reactor model with a high mixing ratio was selected. Powder bed fusion based metal additive manufacturing process was performed to manufacture the 3D microchannel-based chemical reactor. It is expected that the proposed reactor could be applied to a high-efficiency reactor system to produce various chemical materials. For instance, it was possible to perform a chemical reaction based on a toxic material, such as, dimethylformamide solution, using the proposed 3D metal microchannel-based reactor.
With the development of Additive Manufacturing process, lattice structures have recently been fabricated with fine quality. Lattice structures have unique performances which encompass various elastic responses. In this study, shear characteristics of the lattice structures (BCC and OTC) fabricated by SLM process, under optimized manufacturing conditions, were analyzed by 1/4 compression tests. As a result, several fracture modes and elastic configurations were found by comparing the compression test results of various lattice structures. In addition, the lattice structures possessed certain shear elasticity and normal elasticity among different types of lattices at elastic region when shearing. As the 1/4 compression test was simulating the lattice structure on concentrate load or shearing load, the test represented shock introspection characteristics of the lattice inner structure.
In this study, design for additive manufacturing (DfAM) of release agent injection manifold for hot forging has been performed to achieve weight reduction and flow path optimization. The weight reduction of 53.5% was achieved, thereby enabling the application of stainless steel 316L, which has high strength and corrosion resistance. Lightweight manifolds using Al-Mg-10Si and SUS316L materials were fabricated by PBF-type metal 3D printer. The feasibility test showed that mold life was improved by 14% by solving residual release agent problem. In addition, the flow path optimization results suggested that the flow standard deviation of each outlet dropped sharply from 264 to 75 ㎤/s. This approach demonstrated that DfAM for release agent manifold could be applied to increase mold life and improve product quality and productivity for hot forging.
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Optimize Design of Flow Divider and Verification of the PBF 3D Printing Process Jae-Hwi Lee, Jae-Ho Shim, Dong-Hun Sin, Yong-Seok Yang, Dong Soo Kim Journal of Flexible and Printed Electronics.2024; 3(2): 249. CrossRef
Additive Manufacturing for Rapid and Precise Pattern Formation in Shoes Mold Seok-Rok Lee, Eun-Ah Kim, Ye-Rim Kim, Dalgyun Kim, Sunjoo Kim, Soonho Won, Hak-Sung Lee Journal of the Korean Society for Precision Engineering.2023; 40(3): 211. CrossRef
Owing to recent advances in additive manufacturing technology, design for additive manufacturing (DfAM) has been used to overcome design limitations due to constraints in traditional manufacturing processes. In this study, we applied DfAM technology to design lightweight and consolidated vacuum grippers for inspection equipment. We proposed a consolidated design to reduce manufacturing time and costs, which previously encompassed assembling eleven components. Topology optimization was used to reduce part weight while maintaining structural rigidity and safety, and two optimization models were designed: two-piece and one-piece models. Based on these optimized geometries, the internal vacuum paths were designed in a curved shape to enhance adsorption characteristics. Numerical simulations were conducted to evaluate the structural performance and flow characteristics of the initial design and the two optimization models. The pressure drop of the one-piece model, which was the best design, was reduced to 1/8 of the initial design and the structural safety factor was predicted to be 6.37. This final design was then additively manufactured by a digital light processing type 3D printer and the weight of the resulting parts was reduced from 12.94 to 2.08 g. Experimental observation found that the additively manufactured vacuum gripper showed enhanced absorption performance compared to the initial design.
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A Study on Improvement of Flow Characteristics of TPMS Heat Exchanger based on Mathematical Filtering Seo-Hyeon Oh, Jeong Eun Kim, Ji Seong Yun, Do Ryun Kim, Jungwoo Kim, Chang Yong Park, Keun Park Journal of the Korean Society for Precision Engineering.2024; 41(7): 541. CrossRef
A Study on Injection Mold Design Using Topology Optimization Mi-Jin Kim, Jae-Hyuk Choi, Gyeng-Yun Baek Journal of the Korean Society of Manufacturing Process Engineers.2022; 21(4): 100. CrossRef
This paper proposed the simulation model of the servo system with three-stage reducer and presented the result of frequency analysis of the servo system considering backlash ratios and motor input voltage. By virtue of this work, we realized that if the motor input voltage of the system was large, the influence of each stage backlash ratio could be minimized or removed. Besides, we also found that if the motor input voltage was small, this created an optimal backlash ratio combination which could maximize the anti-resonance and resonance frequency of the servo system. This paper could be useful for determining each stage backlash ratio in designing a three-stage geared servo system with fast response.
The robot industry has greatly improved over the past 50 years. It is expected that in the era of the 4th industrial revolution the field of applying robots will expand. Motors are essential in order to operate and control robots. However, robots’ precision requires the application of robot reducers. In particular, many types of harmonic drive reducers have been applied to robots. Harmonic drive reducers have theoretically zero-backlash, but they actually exist for tolerances of Oldham coupling parts. In this paper, dynamic analysis adapted dimensional tolerances of oldham coupling was used to figure out the system backlash characteristics of harmonic drives.
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Method for Radial Stiffness Measurement of Strain Wave Gear Flexspline Sangwoong Lee, Daegwon Koh, Jong-Geol Kim, Murim Kim Journal of the Korean Society for Precision Engineering.2024; 41(12): 923. CrossRef
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