Journal of the Korean Society for Precision Engineering

Structural Analysis of a Cylindrical Superelastic Shape Memory Alloy Ligation Clip: Sang Wook Lee, Jae Hoon Kim, Jae Sung Cha, Ji Hoon Kang; J. Korean Soc. Precis. Eng. 2025;42(11):959-964.
Published online November 1, 2025; DOI: https://doi.org/10.7736/JKSPE.025.083

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This study outlines a structural design process for a cylindrical superelastic shape memory alloy (SMA) ligation clip. Although polymer-based clips are widely used, they face challenges related to long-term stability and limited radiopacity, highlighting the necessity for metal clips. By systematically modifying two key design variables—the hole offset ratio and the cut-off ratio—the proposed clip effectively reduces excessive stress concentration and enhances superelastic behavior. Finite element analyses indicate that the stress deviation in the two cross-sectional deformation regions decreased by 83.9%, and the martensitic transformation remained confined to a small area, demonstrating robust strain recovery within the superelastic range. In conclusion, the improved SMA clip successfully withstood internal pressures exceeding 15 psi without leakage, showcasing its superior ligation performance and potential for durable, reliable use in minimally invasive surgical procedures.

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The Current Status of Domestic and Foreign Technology and Future Development Direction on Shape Shifting Drone: Joo Hyun Baek; J. Korean Soc. Precis. Eng. 2025;42(6):455-469.
Published online June 1, 2025; DOI: https://doi.org/10.7736/JKSPE.025.031

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This paper deals with the current technology status and technology development direction on shape shifting drone. A shape shifting drone is defined as a drone for which its shape and/or function of its platform in flight can be changed by shape shifting technology in order to fulfill a variety of missions effectively in harsh mission environment. A shape shifting drone can be classified as a rotary-wing based, a fixed-wing based, or a biomimetic based shape shifting drone. This work describes technology trends of domestic and foreign countries. It identifies core technologies and development direction. This work will be useful for planning research and development programs on required technology for the development of shape shifting drone in the future.

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Optical Performance Using the Surface Form Error Modeling based on A Monte-Carlos Simulation of An Optical Window: Kwang-Woo Park, Ji-Hun Bae, Chi-Yeon Kim; J. Korean Soc. Precis. Eng. 2024;41(9):725-729.
Published online September 1, 2024; DOI: https://doi.org/10.7736/JKSPE.024.076

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As system performance continues to improve at higher resolutions, it becomes increasingly important to establish standards for imaging degradation caused by optical windows. In this study, random surface shapes were simulated on large area optical windows with peak-to-valley (P-v) values of 0.25, 0.5, and 1.0 λ. Modulation Transfer Function (MTF) values were derived for 1,000 cases per P-v value using Monte-Carlo simulations. The specifications achieved a surface accuracy of 0.5 λ and a parallelism of 0.01 mm. MTF measurements showed that the system MTF was 13.5% prior to the installation of the optical window, and 13.1% after installation. This indicates a degradation rate of approximately 3%.

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Fabrication of Dual-morphing Vascular Stents Using Additive-lathe Printing of Shape Memory Polymers: Yuseok Kim, Seung Mun Lee, Suk-Hee Park; J. Korean Soc. Precis. Eng. 2023;40(10):797-803.
Published online October 1, 2023; DOI: https://doi.org/10.7736/JKSPE.023.077

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In this study, we present the fabrication of dual-morphing vascular stents using an additive-lathe printing method and two different shape-memory polymers. Traditional additive manufacturing techniques confront significant challenges in producing vascular stents with complex, hollow, mesh-like structures due to limitations such as a flat printing bed and the placement of supports. To overcome these obstacles, we employed a lathe-type additive manufacturing system with a rotatable base substrate, enabling precise fabrication of cylindrical-shaped stents. To achieve shape transformability, we used shapememory polymers as the stent materials, offering the advantage of minimally invasive surgery. Two distinct shape-memory polymers, with different transition temperatures (35 and 55oC), were printed using the additive-lathe method. The printed stents consisted of two distinct parts that underwent dual-stage morphological changes at the different temperatures. By manipulating the printing paths, the dual-morphing properties of the stents could be adjusted in both longitudinal and circumferential directions. This innovative approach could be a solution to several limitations associated with the application of stents in diseased vascular tissues with complex shapes, facilitating minimal invasion during surgical procedures.

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Design, Fabrication, and Control of a Rotary Manipulator driven by Twisted Shape Memory Alloy (SMA) Wires: Gil-Yong Lee, Su-Yeon Lee; J. Korean Soc. Precis. Eng. 2023;40(8):665-673.
Published online August 1, 2023; DOI: https://doi.org/10.7736/JKSPE.023.039

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The objective of this study was to present a rotary manipulating system driven by a rotary actuator based on twisted shape memory alloy (SMA) wires. The rotary actuator was composed of two oppositely twisted SMA wires connecting a rotor and a stator through a shaft. Two oppositely twisted SMA wires could generate bidirectional rotary motions upon actuation of each twisted SMA wire corresponding to the direction against the twist direction of each SMA wire. A manipulator was designed and fabricated by integrating manipulating arms, the rotary actuator, and a Hall effect magnetic rotary encoder which could measure the angular position of the rotary motion. We modeled and characterized the manipulator upon application of a ramp current input to each twisted SMA wire. A proportional-integral-derivative (PID) controller was designed and implemented to control the proposed rotary manipulator. Reference angular position tracking performances of the manipulator were evaluated with a series of experiments.

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Effect of Cross Section of Glass Fiber and Injection Conditions on the Warpage and Gloss in GFRP Injection Molding: Il Yong Han, 박성현 , Min Soo Cheong, Tae Kyun Kim, Dong Sam Park; J. Korean Soc. Precis. Eng. 2023;40(2):123-130.
Published online February 1, 2023; DOI: https://doi.org/10.7736/JKSPE.022.127

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SFT, which has a high glass fiber content, is one of the effective methods to replace metal and secure weight reduction and price competitiveness. Also, paintless injection molding in which a functional pattern is applied to the mold surface can eliminate the cost of painting. In this study, three types of SFTs were manufactured by adding round glass fibers measuring Φ7 and Φ10 μm and flat glass fiber measuring 27 × 10 μm for the experiment. DOE (Design of Experiment) was conducted to confirm the change in the warpage of the product and the gloss of the micro pattern due to the cross-sectional shape of glass fibers and the major injection conditions. Based on the results, it was identified that the flat SFT had a very small warpage compared to the round SFTs, and the holding pressure was the main factor in the warpage of all three SFTs. The Φ7 μm SFT had the largest gloss value, and the Φ10 μm SFT and the flat SFT had similar average values. All SFTs demonstrated an enormous change in gloss according to the change in mold temperature. The flat SFT had the smallest standard deviation in both warpage and gloss.

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A Study on the Prediction Model of the Radius of Curvature of the Subtle Feature of the Automotive Parts for Different Forming Conditions: Jae-Hyeong Yu, Kyu-Seok Jung, Yunchan Chung, Chang-Whan Lee; J. Korean Soc. Precis. Eng. 2023;40(1):49-55.
Published online January 1, 2023; DOI: https://doi.org/10.7736/JKSPE.022.101

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The subtle feature is one of the characteristic lines and represents the most noticeable line in the automotive panel. In this study, we proposed a method to predict the radius of curvature of products according to the material, its thickness, its punch angle, and its punch radius. The radius of curvature was divided into three regions, namely, the non-linear, transition, and linear regions. In the non-linear region, the prediction model for the radius of curvature with different forming conditions was derived using the finite element analysis. In the linear region, the radius of curvature was assumed to be the sum of the punch radius and the thickness of the material. In the transition region, a model connecting two regions (Non-linear and linear region) was developed based on the continuity condition. The prediction model presented a very small RMSE with the value of 0.314 mm. Using the prediction model, the radius of curvature with various forming variables could be predicted and the required radius of punch, to obtain a certain value of the radius of curvature, could be precisely predicted.

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Effect of Cross Section of Glass Fiber and Injection Conditions on the Tensile Strength in GFRP Injection Molding: Il Yong Han, Sung Hyun Park, Min Soo Cheong, Tae Kyun Kim, Dong Sam Park; J. Korean Soc. Precis. Eng. 2022;39(12):947-954.
Published online December 1, 2022; DOI: https://doi.org/10.7736/JKSPE.022.109

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SFT, which has a high glass fiber content, is one of the effective methods to replace metal and secure weight reduction and price competitiveness. This study evaluated the effect of glass fiber shape on mechanical properties in injection molding by fabricating SFT with a glass fiber content of 60%. Three types of SFTs were manufactured by adding round glass fibers of Φ7 μm and Φ10 μm and flat glass fibers of 27 × 10 μm. DOE (Design of Experiment) conducts to confirm the change in tensile strength due to changes in significant injection conditions. As a result of the experiment, Φ7 μm SFT and flat SFT have similar tensile strength and Φ10 μm SFT showed the lowest tensile strength value. As for the standard deviation of strength value, the Φ7 μm SFT had the largest standard deviation, and the Φ10 μm SFT showed the slightest change in the injection conditions. In flat SFT, it confirms that the tensile strength increased as the molding temperature increased. The fracture surface observes using SEM. It founds that the tensile strength lowers due to the small glass fiber density and many pullouts at the fracture surface of Φ10 μm with weak strength.

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Enhancing Adhesive Strength between Metal and Plastic in Smartphone Applications
Moon-Soo Kim, Jin-Hyung Park, kang-Suk Choi, Seon-Mi Park, Seong-Dae Choi
Journal of the Korean Society of Manufacturing Process Engineers.2025; 24(9): 82. CrossRef

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A Study on Conformal Heating of Curved Mold Using CNT Film Heater: Seo-Hyeon Oh, Eun-Ji Jeon, Hyeon-Min Lee, Yeong-Bae Ko, Keun Park; J. Korean Soc. Precis. Eng. 2022;39(7):469-475.
Published online July 1, 2022; DOI: https://doi.org/10.7736/JKSPE.022.056

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Injection molding is one of most widely-used polymer processing technologies in which hot polymer fills a mold cavity, and is solidified during the subsequent cooling process. In the mold filling stage, the mold temperature should be high to improve flow characteristics, and low to reduce cooling time during the cooling stage. To fulfill these objectives, rapid mold heating technology has been developed to raise mold temperature, without significant increase in cycle time. While the conventional rapid heating technologies required dedicated facilities such as steam heating or high-frequency induction heating system and has a limitation in uniform heating, the purpose of this study was to develop a facile and conformal mold heating unit that uses a carbon nanotube (CNT) film heater. The CNT film heater was used to heat a curved mold with high temperature uniformity, by maintaining uniform distance from the mold surface. The developed conformal heating technology was then applied to a singly curved mold and a multiply curved mold. Considering that the resulting temperature uniformity is superior to the conventional oil heating, the conformal mold heating technology using the CNT film heater can be used to improve part quality and productivity in various molding processes.

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Design and Fabrication of a Millimeter-Scale Rotary Actuator based on the Twisted Shape Memory Alloy (SMA) Wires: Eun-Jeong Jang, Su-Yeon Lee, Kyung-Hwan Kim, Gil-Yong Lee; J. Korean Soc. Precis. Eng. 2022;39(6):403-410.
Published online June 1, 2022; DOI: https://doi.org/10.7736/JKSPE.022.034

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Shape memory alloy (SMA) has been widely used for many engineering and scientific applications, because it is largely deformable with high power density, and can be actuated easily by resistive heating. It is possible to reduce the size of the actuators by integrating or embedding SMA into the structures. While many applications have been reported regarding linear or bending actuators using the SMA wire, the development of a rotary actuator remains important and challenging for the engineering applications. Here, a new type of millimeter-scale rotary actuator is proposed based on the twisted SMA wires. SMA wires are twisted, folded, and integrated into the rotary actuator, and simple change of the twist direction enables the rotary actuator to rotate in the opposite direction. By integrating the oppositely twisted SMA wires into one rotary actuator unit, bidirectional rotary motions are possible. The actuation mechanism, design, and fabrication processes of the proposed rotary actuator are presented and demonstrated with its actuation performance. The fabricated actuators had average rotary working ranges from -38.68±4.92 deg to +45.37±8.79 deg in counterclockwise (CCW) and clockwise (CW) directions. This study will leverage the practical advances in the relevant engineering and scientific applications.

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A Novel Force-Couple SMA Rotary Actuator for MEMS Safety and Arming Device
Yun Cao, Zeyi Chai, Yikang Huang, Mo Yang, Hengbo Zhu, Weirong Nie, Zhanwen Xi
IEEE Sensors Journal.2025; 25(19): 35879. CrossRef
Multi-field coupled dynamics for a movable tooth drive system integrated with shape memory alloys
Lizhong Xu, Zhenglong Fu
Heliyon.2023; 9(7): e17531. CrossRef
Design, Fabrication, and Control of a Rotary Manipulator driven by Twisted Shape Memory Alloy (SMA) Wires
Gil-Yong Lee, Su-Yeon Lee
Journal of the Korean Society for Precision Engineering.2023; 40(8): 665. CrossRef
Largely deformable torsional soft morphing actuator created by twisted shape memory alloy wire and its application to a soft morphing wing
Su-Yeon Lee, Gil-Yong Lee
Scientific Reports.2023;[Epub] CrossRef

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Design and Evaluation of Soft Actuators Including Stretchable Conductive Fibers: Hye Won Lee, Yeji Han, Minchae Kang, Ju-Hee Lee, Min-Woo Han; J. Korean Soc. Precis. Eng. 2022;39(4):307-313.
Published online April 1, 2022; DOI: https://doi.org/10.7736/JKSPE.021.113

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In this study, soft actuators comprising conductive fibers, flexible polymers, and shape memory alloys, which can be used as textile products, are introduced. Conductive fibers play an important role because they can be used as sensors in wearable devices. The conductive fiber introduced in this study is a form that can be combined with a polymer, and it comprises a form wrapped around a flexible polymer. When an electric current is applied to the shape memory alloy embedded in the polymer, macroscopic deformation occurs due to phase transformation from the Martensite to the Austenite phase. Conductive fibers used in soft actuators are affected by resistive heat generated by the shape memory alloy and bending deformation of the actuator. Accordingly, changes in the conduction properties of conductive fibers were observed due to bending deformation and temperature changes. We also fabricated soft actuators with different types of polymers and observed the differences. The soft actuator presented in this study is a one-piece combination of a conductor and an actuator using a textile-type conductor, and it is likely to be used in smart clothing applications.

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Study of Damper Shape for Vibration Reduction Effect of Treadmill: Hyuk Dong Kwon, Kyeong Su Ha, Dong Hwan Park; J. Korean Soc. Precis. Eng. 2021;38(1):35-41.
Published online January 1, 2021; DOI: https://doi.org/10.7736/JKSPE.020.053

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As interest in the quality of life has recently increased, there is a growing interest and demand for exercise equipment, such as indoor treadmills or cycles, which can be used at home. However, the use of such indoor exercise equipment has caused social problems by generating noise between floors and causing inconvenience to neighbors. In particular, treadmills that generate a lot of vibration during use cause more social problems in an assembly building, such as an apartment. The purpose of this study is to design dampers of various shapes and to develop dampers with high vibration damping effects through vibration analysis. The damper was installed at the lower end of the treadmill to reduce vibration from the product. Three types of dampers were designed by referring to the damper shape of the existing treadmill, and the vibration reduction effect of each damper shape was verified through structural analysis of the magnitude of vibration generated from the bottom surface of each damper.

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A Precision Line Profile Measurement Technique Using Multi Probe Error Separation Method: Sang Woo Baek, Nahm Gyoo Cho; J. Korean Soc. Precis. Eng. 2020;37(9):643-651.
Published online September 1, 2020; DOI: https://doi.org/10.7736/JKSPE.020.052

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In this research, a precise on-machine line-profile measuring system that compensates for the motion-error from the linear-guide, which can influence the accuracy of the measurement of the profile was developed. For this purpose, the principle of measuring the system model was used to analyze the compensating motion error component for line-profile and 3 types of MPES method (Integration-Method, the Fourier-Model-Method, and the Sequential-Method). The multi-probe-error-separation-method (MPES) was applied to calculate the motion-error, which in turn was used to compensate for the measured linear-profile of the specimen. Lastly, the simulation conditions involving a multi-probe measurement system consisting of a reference-artifact, capacitive-sensor, and three displacement-sensors were designed and Monte-Carlo simulation was implemented for the evaluation of the 3 types of MPES method. Also, the simulation results obtained from the conventional measuring system and the proposed system were compared for the verification of the performance of the latter. Consequently, efficient compensation of the motion error appeared as possible and the applicability of the multi-probe measurement system was confirmed.

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Feasibility Study on Dimensional Standard for Material Extrusion Type 3D Printed Structures: Sunghoon Eom, Jungjae Park, Jonghan Jin, Yong Son; J. Korean Soc. Precis. Eng. 2020;37(4):241-246.
Published online April 1, 2020; DOI: https://doi.org/10.7736/JKSPE.019.118

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Material extrusion (ME) type 3D printing has been widely utilized through various types of systems depending on the fabrication methods, materials, and precision to fabricate complex workpieces that cannot be made with conventional methods. This study provides basic considerations in response to the current demands on performance evaluation of ME type 3D printing related to dimensions as well as the realization of the guidelines to be established in the near future. As a simple specimen for these purposes, 2D and 3D hole-plates were designed and fabricated by using a ME type entry-level 3D printer. For evaluation of dimensions on the specimen, both specimens were measured by a calibrated tool-maker’s microscope which is to length standard. The measurement parameters were the center position of the holes, the diameter of the holes, and the circularity error of the holes.

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A Study on 3D Printing Conditions Prediction Model of Bone Plates Using Machine Learning
Song Yeon Lee, Yong Jeong Huh
Journal of the Korean Society for Precision Engineering.2022; 39(4): 291. CrossRef
Dimensional Characteristics of Hydraulic Actuator Curve based on 3D Printing Filament Materials
Myung-Hwi Jung, Jeong-Ri Kong, Hae-Ji Kim
Journal of the Korean Society of Manufacturing Process Engineers.2021; 20(1): 74. CrossRef
Effect of Fused Deposition Conditions on the Fracture Behavior of 3D Printed Tensile Specimens
Bum Joon Kim
Journal of the Korean Society for Precision Engineering.2020; 37(6): 421. CrossRef

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A Numerical Study on the Cooling Efficiency of the Gas Turbine Vane with the Film Cooling Hole Shape: Jaehun Choi, Hwabhin Kwon, Heesung Park; J. Korean Soc. Precis. Eng. 2020;37(2):107-113.
Published online February 1, 2020; DOI: https://doi.org/10.7736/JKSPE.019.094

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Research on advanced cooling system design is significant in achieving a high turbine inlet temperature in the gas turbine industry. The higher turbine inlet temperature of the gas turbine increases thermal efficiency. However, it also aggravates the gas turbine deterioration, lifespan, and efficiency. In this study, a numerical model is developed for simulating the cooling performance of the gas turbine vane with the turbine inlet temperature of 1528 K. The impact of the coolant air flow rate and hole-shape were investigated. The expanded hole shape had better cooling performance than the general cylindrical shape, and showed higher cooling efficiency. We suggest that there is a relationship between the shape of the film cooling holes and the cooling air flow rate that achieves the desired cooling effectiveness.

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