Journal of the Korean Society for Precision Engineering

Study on UV Energy Effects in High Aspect Ratio Patterning via the Self-propagating Photopolymer Waveguide (SPPW) Method: Jun Ho Song, Woo Young Kim, Seungwoo Shin, Seok Kim, Young Tae Cho; J. Korean Soc. Precis. Eng. 2025;42(9):757-762.
Published online September 1, 2025; DOI: https://doi.org/10.7736/JKSPE.025.041

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This study quantitatively examines the impact of ultraviolet (UV) intensity and energy on the formation of high aspect ratio (HAR) microstructures using the Self-Propagating Photopolymer Waveguide (SPPW) process. This mechanism relies on the self-focusing of UV light within a refractive index gradient, allowing the light to propagate and polymerize vertically beyond the initial exposure zone. Experiments were performed at UV intensities of 7.5, 12.5, and 17.5 mW/cm², with energy levels ranging from 0.0375 to 13.5 J/cm². The results indicated that a lower UV intensity of 7.5 mW/cm² produced uniform and vertically elongated structures, achieving a maximum aspect ratio of 12.26 at 0.9 J/cm². In contrast, higher UV intensities led to lateral over-curing, base expansion, and shape distortion, primarily due to rapid polymerization and the oxygen inhibition effect. These findings emphasize the importance of precisely controlling both UV intensity and energy to produce uniform, vertically aligned HAR microstructures, offering valuable insights for optimizing the SPPW process in future microfabrication applications.

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A Study on How to Utilize Digital Twin-based Machine Learning and Openpose for Poppy Robot’s Motion Control: Bum Jin Kim, Seok Kim, Young Tae Cho; J. Korean Soc. Precis. Eng. 2024;41(5):401-405.
Published online May 1, 2024; DOI: https://doi.org/10.7736/JKSPE.024.008

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The key components of smart manufacturing, a central concept in the era of the 4th Industrial Revolution, consist of digital twin technology, AI, and computer vision technology. In this study, these technologies were utilized to govern the Poppy robot, a humanoid robot designed for educational and research purposes. The digital twin creates a virtual environment capable of real-time simulation, analysis, and control of the robot’s motions. The digital twin of the robot was constructed using Unity, a 3D development program. Motion data was captured while simulating the physical structure and movements of the virtual robot. This data was then fed into a Tensorflow-based deep neural network to generate a regression modelthat predicts motor rotation based on the position of the robot’s hand. By integrating this model with a Python-based robot control program, the robot’s movements could be effectively managed. Additionally, the robot was controlled using Openpose, a computer vision algorithm that predicts characteristic points on a human body. Position data for human joint points was collected from 2D images, and the motor angle was calculated based on this data. By implementing this approach on an actual robot, it became possible to enable the robot to replicate human movements.

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Development of a Machine Learning-Based Predictive Model for the Structural Safety of an Optical Table Air Springs Using Simulation Data
Hwi Jun Son, Young Tae Cho
Journal of the Korean Society of Manufacturing Process Engineers.2025; 24(12): 105. CrossRef

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A Study on the Dissolution Characteristics of 3D Printed Tablet with Lattice Structures: Sang Hoon Lee, Seung Min Oh, Seo Rim Park, Seok Kim, Young Tae Cho; J. Korean Soc. Precis. Eng. 2023;40(8):633-638.
Published online August 1, 2023; DOI: https://doi.org/10.7736/JKSPE.023.002

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With recent development of 3D printing technology, its applications to the bio-industry are increasing. Many research studies are being done for manufacturing personalized tablets through this technology in the pharmaceutical process. In this study, to control the dissolution rate of tablets, a lattice structure was inserted into the tablet and the dissolution rate was compared. The tablet proposed in this study can be manufactured by the FDM method, adopting a lattice structure with a large surface area-to-volume ratio. Tablets containing various lattice structures were fabricated using water-soluble PVA filaments and dissolution experiments were conducted in water at 37oC. As a result, it was confirmed that the specific surface area and the mass loss rate were proportional to both the 3D lattice structure and the monolith structure. Among different structures, the diamond structure had the most active dissolution.

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Forged Molding for Strength Improvement of Eccentric Head Bolts: Young Tae Cho; J. Korean Soc. Precis. Eng. 2023;40(3):197-202.
Published online March 1, 2023; DOI: https://doi.org/10.7736/JKSPE.022.152

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In this study, the production process of eccentric head bolts that fasten flanges for water supply pipe connections, which can only be achieved through the cold forging process, was improved. For axial forging, forming analysis was performed for a 200-ton header machine to check the raw material specifications, forming load, and metal flow improvements suitable for forming. The analysis found that the forging of high-strength bolts of M14×65 ㎜ with eccentric heads was possible under the maximum load condition of 137.2 tons with low carbon boron steel of ø13.8×89.7 ㎜ and 105.2 g. By mounting the prototype mold on the header machine, it was possible to prevent metal flow breakage, as shown by the trial mass production test. It was possible to improve the strength of the eccentric head bolt and reduce the weight of the input material through the cutting process. Therefore, manufacturing costs could be reduced.

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Energy Saving of Rubber Forming by Direct Heating Press Mold Development: Young Tae Cho; J. Korean Soc. Precis. Eng. 2022;39(7):485-491.
Published online July 1, 2022; DOI: https://doi.org/10.7736/JKSPE.022.049

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Rubber is positioned as an important material and essential tool and means for mass production of products in all industries due to its unique properties such as sealing, elasticity and shock absorption. However, in the case of conventional press rubber molding, its energy efficiency is low due to considerable heat loss, and the deviation of the temperature distribution of the molding mold is high due to the indirect heating method in which heat is transferred to the upper and lower molds installed on hot plates. The upper and lower heating plates were heated by several heaters installed on the hot plates. The high deviation of the temperature distribution causes unformed defects. Among the rubber mold working methods that consume considerable energy, this study attempted to reduce energy consumption by directly heating the mold via installing a heater inside the upper and lower molds in a compression mold with large energy loss. As a result, compared to the conventional method of transferring heat to the mold by heating the hot plate of the press, energy was saved by 30%, the initial mold heating time was shortened by 20 minutes, and the product defect was reduced with a rate of 25%.

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Enabling Technologies for Thermal Management During Permanent Mold Casting: A Critical Review
Cheolmin Ahn, Carl Söderhjelm, Diran Apelian
International Journal of Metalcasting.2025;[Epub] CrossRef

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A Study on the Implementation of Virtual Motion Control in Wire Arc Additive Manufacturing Process Using Robot Simulator: Chang Jong Kim, Seok Kim, Young Tae Cho; J. Korean Soc. Precis. Eng. 2022;39(1):79-85.
Published online January 1, 2022; DOI: https://doi.org/10.7736/JKSPE.021.076

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Recently, industrial manufacturing has developed into additive manufacturing, benefiting from multi-item small-sized production and effective manufacturing. Importantly, Wire Arc Additive Manufacturing, which uses metal wires, is attracting worldwide attention for its high-quality metal product technology. Technological innovation that combines virtual physics with reality through big data communication, such as process variables along with Wire Arc Additive Manufacturing, is an essential task for implementing smart manufacturing technology. Due to the characteristic of Wire Arc Additive Manufacturing, numerous variable conditions exist, making it difficult to standardize robot"s process path data generation algorithms and data application methods, and this data generation method is being studied as a core element technology. The present study generated foundation process implementation, simulation, and generated path data for robots in virtual space using RoboDK, which provides robot libraries from multiple manufacturers, and Python, which is a universal programming language. To implement the experimental data in practice, ABB"s industrial six-axis robots IRB-6700 and Fronius TPS500i were used to control the arcing plasma heat source, and the process path worked the same as simulation. Based on the underlying experimental results, this process can be applied to generation of additive manufacturing in the Wire Arc Additive Manufacturing process for 3D models.

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Artificial Intelligence Technologies and Applications in Additive Manufacturing
Selim Ahamed Shah, In Hwan Lee, Hochan Kim
International Journal of Precision Engineering and Manufacturing.2025; 26(9): 2463. CrossRef
In-situ remanufacturing of forging dies for automobile parts based on wire arc directed energy deposition
Chang Jong Kim, Chan Kyu Kim, Hui-Jun Yi, Seok Kim, Young Tae Cho
Journal of Mechanical Science and Technology.2024; 38(9): 4529. CrossRef

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Unconventional Additive Manufacturing for Multiscale Ceramic Structures: Hyo Jun Lee, Young Tae Cho, Seok Kim; J. Korean Soc. Precis. Eng. 2021;38(9):639-650.
Published online September 1, 2021; DOI: https://doi.org/10.7736/JKSPE.021.072

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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

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Analysis of Compression Behavior on 3D Microlattices Coated with Metal Nanoparticle-Polymer Composites: Seo Rim Park, Do Hyeog Kim, Seok Kim, Young Tae Cho; J. Korean Soc. Precis. Eng. 2021;38(9):631-637.
Published online September 1, 2021; DOI: https://doi.org/10.7736/JKSPE.021.071

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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

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Finding Ways to Deform Fine Patterns Fabricated by UV Curable Resin: Woo Young Kim, Su Hyun Choi, Seonjun Kim, Young Tae Cho; J. Korean Soc. Precis. Eng. 2020;37(4):291-296.
Published online April 1, 2020; DOI: https://doi.org/10.7736/JKSPE.019.141

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In this study, experiments were performed to determine if the pattern fabricated by the UV nano imprint process could be modified using additional processes such as surface treatment. We wanted to confirm the fabrication possibility of a special pattern such as the reverse trapezoidal shape difficult to produce because of the releasing problem. The UV ozone treatment (Hydrophilic Treatment) and OTS coating (Water Repellent Treatment) were used and shape modification occurred under controlled treatment time. As a result of performing the UV ozone treatment for 30 minutes or more on a micro pattern manufactured by UV curing resin of PUA series, the contraction phenomenon of the micro structure occurred and the shrinkage was dependent on treatment time. When the OTS treatment was performed, the surface of the microscale pattern could be roughened. When the nanoscale pattern was treated, the pattern change could be induced. It was possible to partially cure the resin by adjusting the UV absorption using dye material, and the deformation of the pattern was made by an additional pressing process. As a result of the experiment of the various methods causing the shape change of the cured pattern, the possibility of the methods was verified.

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Development of a Software for Path Planning in Wire Arc Additive Manufacturing: Chi Woo Ahn, Do Hyeog Kim, Chan Kyu Kim, Young Tae Cho; J. Korean Soc. Precis. Eng. 2020;37(2):149-155.
Published online February 1, 2020; DOI: https://doi.org/10.7736/JKSPE.019.088

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Along with the recent spread of 3D printing technology, researchers have developed various materials and equipment, now widely disseminated among individuals and industries. However, most of the current metal 3D printers generate the cutting paths using cutting software only, which doesn’t consider heat input of the plasma or laser. In the wire arc additive manufacturing (WAAM) system, a projection algorithm is created through the CATIA application programming interface. Different from the existing cutting algorithm, this algorithm converts a two-dimensional (2D) image into a three-dimensional (3D) structure by orthogonal projection and a voxel algorithm that expresses a 3D finite volume element. To fix the (x, y) coordinates and the z (Height) coordinate to be on the 2D plane, the projection algorithm models the 3D geometry orthogonal to the 2D plane. The bead modeling data and the step-over values generating the laminate shape were determined. The core of the voxel algorithm that models the free-shape lamination obtains the point location of the wire arc, considering the bead size and the distance between the layer spacing and the voxel center point (According to the processing conditions). Finally, the correct projection and voxel algorithms are selected using a lamination path-acquisition strategy.

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Analysis of Endmill Cutting Characteristics Based on the Machining Path during Postprocessing of Wall-shaped Structures Fabricated by Wire Arc Additive Manufacturing
Hwi Jun Son, Seok Kim, Young Tae Cho
Journal of the Korean Society of Manufacturing Process Engineers.2024; 23(3): 44. CrossRef
Parameter Optimization of WAAM with Pulsed GMAW for Manufacturing Propeller-Shaped Blade
Sang-Woo Han, Hojin Yoo, Seungcheol Shin, Hansol Kim, Geonho Lee, Jongho Jeon, Sangjun Han, Jungho Cho
International Journal of Precision Engineering and Manufacturing.2023; 24(7): 1103. CrossRef
A Study on the Implementation of Virtual Motion Control in Wire Arc Additive Manufacturing Process Using Robot Simulator
Chang Jong Kim, Seok Kim, Young Tae Cho
Journal of the Korean Society for Precision Engineering.2022; 39(1): 79. CrossRef

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A Study on the End Mill Shape Design for Machining of High Hardness Die Steels by Comparison of Cutting Force: Ju Ho Lee, Young Tae Cho; J. Korean Soc. Precis. Eng. 2019;36(2):141-147.
Published online February 1, 2019; DOI: https://doi.org/10.7736/KSPE.2019.36.2.141

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Heat treated die steels are durable and resistant to abrasion. However, machining them is not very efficient. To improve the machinability using the end-milling process for high hardness die steels, we proposed an end-mill shape through analysis of the cutting force and simulation. In this study, we determined the important factors affecting the cutting force among several elements of end-mill shape using the customized cutting simulator and the design of experiments (DOE) technique. After the selecting the effective factors based on the simulation and DOE results, various end-mills were fabricated by adjusting the parameters. In the experiment, the cutting force between 1 pass and 40 pass were measured and the average value compared with each end-mill shape. Edge radius, radial relief angle and axial relief angle were selected as a key parameters and optimized by measuring the cutting force through repeated and well controlled experiments. In conclusion, the effective factors were confirmed and we could now determine the optimum shape of end-mill to minimize the cutting force for high hardness die steels.

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Diagnosis of Tool Wear and Fracture through Cutting Force Frequency Analysis of Stainless Steel Cutting End Mill Tools
Tae Gyung Lee, Bo Wook Seo, Hwi Jun Son, Seok Kim, Young Tae Cho
Journal of the Korean Society of Manufacturing Process Engineers.2023; 22(12): 88. CrossRef

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A Study on the Enhancement of Industrial Boiler by Air Flow Control: Yong Hee Oh, Yong Seon Mo, Yoon Gyo Jung, Young Tae Cho; J. Korean Soc. Precis. Eng. 2017;34(10):723-727.
Published online October 1, 2017; DOI: https://doi.org/10.7736/KSPE.2017.34.10.723

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Industrial boilers are used in numerous fields, and heat efficiency enhancement is a major topic of study. A double-pipe boiler is a simply structured industrial boiler having a high thermal efficiency. Baffles are specially installed in the doublepipe boiler for increasing the heating time. The baffles determine the heat efficiency of the double-pipe boiler. However, it is theoretically difficult to design a baffle and locate its optimal position, solely by considering the fluid flow of heated air, and the heat exchange between water and heated air. To confirm the correct positioning of baffles, fluid flow and heat transfer simulations were conducted on the boiler. Our results showed that at some points, there was insufficient circulation of heated air. To overcome this problem, baffles were added at these points, by referring to the simulation results. The changing of baffles resulted in an increase in efficiency of heat transfer in the double-pipe boiler.

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New Design of a Fiber Channel-Embedded Set-Top Box for IPTV Networks: Sungwook Chung, Young Tae Cho; J. Korean Soc. Precis. Eng. 2017;34(8):545-550.
Published online August 1, 2017; DOI: https://doi.org/10.7736/KSPE.2017.34.8.545

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The Internet protocol television (IPTV) service enables people to enjoy various Internet-based services via conventional TV watching. In the IPTV system, a set-top box (STB) is the key since it works as a terminal device that can relay real-time multimedia content from the Internet. However, the current IPTV STB functions as an attached device in a local area network although the actual IPTV network is usually served by an optical fiber-based network such as fiber-to-the-home (FTTH). Therefore, we introduce a novel fiber channel (FC)-embedded IPTV STB to fully use the sufficient optical fiber-based network bandwidth such as 1 Gbps. To verify the IPTV network capabilities by impact of the FC-embedded STB, we evaluate the performance of the FC-embedded STB-attached IPTV network architecture via extensible simulations in terms of an average startup-delay, an average reject ratio, and the number of concurrent users. Surprisingly, the suggested IPTV system demonstrates superior average startup-delay (less than 15 msec), an acceptable average reject-ratio less than 3%, and an almost linear increasing number of concurrent users, which reveals that the FC-embedded STB significantly affects the entire FC-AL-based IPTV network performance by efficiently facilitating the broadband optical fiber bandwidth.

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A Study on Selection of Process Conditions through Cross Section Analysis of Laser Cutting of Hastelloy Thin Plate: Chan Gyu Kim, Yoon Gyo Jung, Young Tae Cho; J. Korean Soc. Precis. Eng. 2017;34(8):533-537.
Published online August 1, 2017; DOI: https://doi.org/10.7736/KSPE.2017.34.8.533

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To evaluate the quality of the cross section of Ni alloy thin plate cut by laser, we have proposed an analysis method using SEM image to measure surface roughness of cross section. The surface roughness of the cut area of the thin plate is considerably difficult to analyze using conventional measurement technique such as profile measurement with a probe. When the SEM image is used, the roughness value can be collected quantitatively while judging the surface status qualitatively. A Hastelloy C-276 thin plate with a thickness of 50 μm coated with HTS was cut by Nd:YAG laser, and the state of the cross section was analyzed by applying the proposed method in this research. The optimum laser cutting process condition could be found for the lowest surface roughness.

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A Study on Improved Drill Shape for Efficient Drilling of Inconel 718 Using the Design of Experiment: Do Hyeog Kim, Ki Bum Park, Young Tae Cho, Yoon Gyo Jung; J. Korean Soc. Precis. Eng. 2017;34(3):161-166.
Published online March 1, 2017; DOI: https://doi.org/10.7736/KSPE.2017.34.3.161

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Inconel 718, a typical ultraheat-resistant alloy, is recognized as a useful component in aircraft parts owing to its high-temperature strength and good chemical stability. Although many studies have been conducted to determine the proper drill shape to overcome the poor machinability when drilling into Inconel 718, most have involved a cutting process program known as AdvantEdge, as an experimental approach requires much time and money. In this study, our purpose is to optimize the drill shape for efficient drilling by conducting a trust force and temperature analysis using AdvantEdge. In order to achieve this purpose, the reliability of the results of the analysis was verified and by applying design of experiment an analysis of the geometric parameters of the drill shape considering the thrust force and temperature was conducted.

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Analysis of Cutting Force and Plastic Deformation Occurring During Machining of Ti-6Al-4V Alloy Aircraft Parts
Hwi Jun Son, Seok Kim, Ki-Beom Park, Hyoun Chul Jung, Young Tae Cho
Journal of the Korean Society of Manufacturing Process Engineers.2022; 21(8): 25. CrossRef
Cutting Characteristics and Deformation Analysis for Chord and Side Fitting Parts in an Aircraft Bulkhead
Do Hyeog Kim, Yoon Gyo Jung, Yong-Seon Mo, Young Tae Cho
Journal of the Korean Society of Manufacturing Technology Engineers.2020; 29(1): 74. CrossRef
Study on Deformation Analysis of Holes during Drilling of Aircraft Engine Compressor Cases
Ki-Beom Park, Young-Tae Cho, Yoon-Gyo Jung
Journal of the Korean Society of Manufacturing Process Engineers.2018; 17(3): 65. CrossRef
A Study on the Productivity Improvement of Inconel 718 Material Using Cutting Force Control Program
Seung-Heon Lee, Hwang-Jin Son, Young-Tae Cho, Yoon-Gyo Jung
Journal of the Korean Society of Manufacturing Process Engineers.2017; 16(6): 41. CrossRef