Journal of the Korean Society for Precision Engineering

Laser Ablation Patterning of Metal Thin Films for On-demand of Shadow Mask Patterning in Vacuum Deposition: Beomsun Do, Seunghun Lee, Hyunho Lee, Hoon Jeong, Joel Ndikumana, Kunsik An; J. Korean Soc. Precis. Eng. 2025;42(10):775-782.
Published online October 1, 2025; DOI: https://doi.org/10.7736/JKSPE.D.25.00001

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This study explores the use of laser ablation technology for creating on-demand shadow masks, which are essential in the fabrication of thin film transistor (TFT) devices. Traditional methods for producing shadow masks often encounter significant challenges, such as high costs, lengthy production times, and difficulties in achieving fine, high-resolution patterns. To address these issues, this study introduces a method for manufacturing shadow masks using fiber laser-based laser ablation. Key laser parameters, including frequency and power, were optimized throughout the research. Systematic experimentation revealed that a frequency of 20 kHz and a power output of 14 W enabled the precise and uniform creation of patterns with a 50 μm channel spacing. When these custom shadow masks were employed in the TFT fabrication process, the resulting devices exhibited stable and reliable electrical performance. The findings suggest that laser ablation-based on-demand shadow mask technology offers a cost-effective and flexible solution for producing large-area, high-resolution TFTs. Additionally, this approach significantly reduces the prototyping cycle, making it ideal for rapid development and iterative testing in research and development environments.

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Design of a 3-Axis Compliant Robotic Deburring Tool with Force Sensing and Variable Stiffness Capabilities: Gi-Seong Kim, Jeong-Hyeon Jun, Han Sung Kim; J. Korean Soc. Precis. Eng. 2025;42(3):215-221.
Published online March 1, 2025; DOI: https://doi.org/10.7736/JKSPE.024.107

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In this paper, a deburring tool with 3-axis compliance is presented for deburring using a robot manipulator. Compliance is provided with beam structures instead of pneumatic pressure, which enables integrated 3-axis force sensing and variable stiffness. Two radial compliances were achieved using 4-PSS (Prismatic-Spherical-Spherical) legs, with P joints composed of cantilever beams. The one axial compliance was configured with two ball bushings and a linear spring. Strain gauges were attached to cantilever beams and a load cell was mounted between the linear spring and the universal joint to perform force sensing. The stability of vibrations and force sensing were verified through deburring experiments using the proposed deburring tool. Additionally, experiments on automatic offset for applying a constant force during deburring were conducted and results were validated by comparing the workpiece before and after the deburring process.

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Stress Analysis of a Robot End-Effector Knife for the Deburring Process
Jeong-Jin Park, Jeong-Hyun Sohn, Kyung-Chang Lee
Journal of the Korean Society of Manufacturing Process Engineers.2025; 24(6): 42. CrossRef
Stress Analysis of a Robot End-Effector Knife for the Deburring Process
Jeong-Jin Park, Jeong-Hyun Sohn, Kyung-Chang Lee
Journal of the Korean Society of Manufacturing Process Engineers.2025; 24(6): 42. CrossRef

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Thermal Fatigue Life Evaluation of EB-PVD TBC Using Newly Developed Small-scale Burner Rig: Soo Park, Jun-Young Kim, Jun-Young Kim, Seoung-Ju Kim, Chang-Sung Seok; J. Korean Soc. Precis. Eng. 2025;42(1):65-73.
Published online January 1, 2025; DOI: https://doi.org/10.7736/JKSPE.024.110

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In this study, the effect of flow rate ratio (R) and total flow rate (Q) on the surface temperature of thermal barrier coatings (TBC) was investigated using a newly developed small-scale methane-oxygen burner rig. Subsequently, the failure mode of electron beam physical vapor deposition (EB-PVD) TBC was examined, and the relationship between surface temperature and coating life was established. The surface temperature of the TBC was found to be strongly dependent on both the flow rate ratio and the total flow rate. Specifically, surface temperature exhibited a proportional relationship with total flow rate, while it showed an inverse relationship with flow rate ratio. The failure mode of the EB-PVD TBC involved a gradual increase in delamination from the rim to the center of the coin-shaped specimen, and this failure mode was found to be independent of surface temperature. Additionally, it was determined that the surface temperature of EB-PVD TBC has a perfectly inverse linear relationship with coating life. This finding implies that the derived linear regression line from the burner rig test can be directly used to predict coating life for any untested surface .temperature.

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Study on Miniaturization and Lightweight Method of Electric Thruster Power and Gas Supply Device for Micro Satellite: Jin Young Park; J. Korean Soc. Precis. Eng. 2024;41(11):889-896.
Published online November 1, 2024; DOI: https://doi.org/10.7736/JKSPE.024.090

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Recent advancements in science and technology have enabled even microsatellites to perform various high-level tasks. As the range of missions that satellites undertake expands, even microsatellites now require thrust systems for orbit adjustment and collision avoidance. In such satellite applications, sizes and weights of all electrical components and propulsion systems are restricted, emphasizing the importance of miniaturization and weight reduction. Research is ongoing in various methods to address these needs. To solve these challenges, this study proposed a design model for miniaturizing and lightening both Anode Power Module (APM) and gas supply system. The APM utilizing an LLC resonant converter achieved an efficiency of up to 86%. An evaluation of flow control characteristics of the proposed gas supply device showed that the flow control error was less than 2.3%, indicating effective results. A thermal mass flow sensor was developed to measure the flow of gas. Temperature characteristics derived from experiments were analyzed to assess their applicability to electric thruster systems for satellites.

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Optimized Coverage Path Planning for Efficient Autonomous Operation of a Barn Manure Handling Robot: Goo Jun Ji, Myeong Gyu Lee, Won Gun Kim; J. Korean Soc. Precis. Eng. 2024;41(11):827-840.
Published online November 1, 2024; DOI: https://doi.org/10.7736/JKSPE.024.065

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In the field of robotics and automation, path planning holds significant potential for optimizing field operations. These operations must cover the work area comprehensively and efficiently with minimal movement. To achieve these goals, coverage path planning (CPP) utilizing the Boustrophedon method is essential. However, in an experimental environment, CPP often results in missed work areas due to cumulative sensor errors and structural inconsistencies. This paper aimed to improve CPP by employing the Douglas-Peucker algorithm to simplify the work path and minimizing missed areas. Additionally, Edge Zone Path method was used to generate edge paths, enhancing safety of the trajectory. For experimental purposes, data were acquired from an actual barn. The work area was divided using three segmentation algorithms. Among these, the Voronoi Segmentation, which demonstrated superior performance, was used to extract the data. Experimental results indicated that the proposed optimized CPP improved path safety by maintaining a safe distance from obstacles during frequent turns. Additionally, the Coverage Ratio increased the coverage area of the autonomous robot by an average of 17% compared to the original CPP. These findings suggest that the proposed method can generate more efficient and safe work paths.

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Development of a Vertical Burner Rig Using Methane Flame: Soo Park, Dae-Jin Kim, Jun-Young Kim, Seong-Ju Kim, Ki-Yong Lee, Jeong-Min Kim, Hyung-Ick Kim, Chang-Sung Seok; J. Korean Soc. Precis. Eng. 2024;41(8):653-661.
Published online August 1, 2024; DOI: https://doi.org/10.7736/JKSPE.024.053

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In this study, we developed a new vertical thermal gradient rig that uses methane-oxygen fuel. We conducted thermal gradient testing on a thermal barrier coating system, with a flame temperature of 1,900℃. Our results showed that the maximum surface temperature reached 1,065℃, while the temperature difference between the surface temperature and the temperature of the middle substrate (ΔT) was 70oC. Using the same torch as in this study, our finding suggest that the total flow rate of the flame should be above 12.4 LPM, and the gun distance should be less than 8 cm, to simulate a surface temperature of 1,300℃, while keeping the substrate temperature below 1,000℃. This will ensure that the flame is wide enough to cover the entire surface area of the thermal barrier coating.

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Thermal Fatigue Life Evaluation of EB-PVD TBC Using Newly Developed Small-scale Burner Rig
Soo Park, Dae-Jin Kim, Jun-Young Kim, Seoung-Ju Kim, Chang-Sung Seok
Journal of the Korean Society for Precision Engineering.2025; 42(1): 65. CrossRef

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Development and Application of a Ball-on-plate Balancing System: Sangsin Park; J. Korean Soc. Precis. Eng. 2024;41(3):215-222.
Published online March 1, 2024; DOI: https://doi.org/10.7736/JKSPE.023.139

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The Ball-on-Plate Balancing System is a system where the base is fixed to the ground, and the plate is connected to the base through a spherical joint and can rotate in two directions (X-axis roll rotation, Y-axis pitch rotation). Two rotational joints are located on the orthogonal coordinate line of the base, and these joints are connected to the operational links of a 4-bar linkage, creating rotation of the plate around the spherical joint. The goal of this system is to prevent a ball placed on the plate from rolling off and maintain it at the center of the plate. A 17-inch touch panel attached to the plate allows the orthogonal coordinates of a ball placed on the plate to be measured. A cross-shaped frame was designed to secure the touch panel, and a custom universal joint was centered in this frame. The Ball-on-Plate Balancing System was integrated into a cart table, and a horizontal maintenance system was designed to keep the table level. Experiments confirmed the ability of the table to maintain its horizontal position during movements on uneven surfaces and sudden starts or stops.

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Design of a Controller to Overcome Air Ball in the Ball-on-plate System Applied to a Shelf Cart
Sangsin Park
Journal of the Korean Society for Precision Engineering.2025; 42(4): 301. CrossRef

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A Study on the Shear Characteristics based on the Coverage of Shot-peened Al6061-T6 Bonded with CFRP: Hong Seok Kim, Joon-Hyung Park, Gang-Min Sung, Beom-Joon Kang, Seong-Kyun Cheong, Ki-Hoon Shin; J. Korean Soc. Precis. Eng. 2024;41(1):31-36.
Published online January 1, 2024; DOI: https://doi.org/10.7736/JKSPE.023.081

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In this study, a new method of bonding CFRP and Al6061-T6 with epoxy adhesive after shot-peening treatment on the surface of Al6061-T6 specimens was proposed to improve bonding strength of a single lap joint between CFRP and Al6061-T6. More specifically, correlation between shot peening coverage on the Al6061-T6 surface and bonding strength with CFRP was experimentally analyzed. Experimental results showed that the surface roughness and the bonding strength increased as the peening time on the surface of Al6061-T6 increased up to a specific peening time (or coverage). However, the surface roughness and bonding strength decreased again under an over-peening condition of 480 seconds (300% coverage) or more. Therefore, it is necessary to search for the optimal peening time that can maximize bonding strength as well as the fatigue life of parts at a peening time between 320 (200%) and 480 s (300%) through additional experiments in future studies.

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Application of Deep Reinforcement Learning to Temperature Control of a Chamber for Ultra-precision Machines: Byung-Sub Kim, Seung-Kook Ro; J. Korean Soc. Precis. Eng. 2023;40(6):467-472.
Published online June 1, 2023; DOI: https://doi.org/10.7736/JKSPE.022.124

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Deep reinforcement learning (RL) has attracted research interest in the manufacturing area in recent years, but real implemented applications are rarely found. This is because agents have to explore the given environments many times until they learn how to maximize the rewards for actions, which they provide to the environments. While training, random actions or exploration from agents may be disastrous in many real-world applications, and thus, people usually use computer generated simulation environments to train agents. In this paper, we present a RL experiment applied to temperature control of a chamber for ultra-precision machines. The RL agent was built in Python and PyTorch framework using a Deep Q-Network (DQN) algorithm and its action commands were sent to National Instruments (NI) hardware, which ran C codes with a sampling rate of 1 Hz. For communication between the agent and the NI data acquisition unit, a data pipeline was constructed from the subprocess module and Popen class. The agent was forced to learn temperature control while reducing the energy consumption through a reward function, which considers both temperature bounds and energy savings. Effectiveness of the RL approach to a multi-objective temperature control problem was demonstrated in this research.

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On-Line Model Predictive Control for Energy Efficiency in Data Center: Min Sik Chu, Hyun Ah Kim, Kyu Jong Lee, Ji Hoon Kang; J. Korean Soc. Precis. Eng. 2021;38(12):943-951.
Published online December 1, 2021; DOI: https://doi.org/10.7736/JKSPE.021.068

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It is important to minimize electric energy consumption of a data center that uses enormous electricity for maintaining an adequate indoor temperature. Most data centers have applied the outdoor air cooling method on account of economic feasibility. However, it is necessary that data centers have an efficient control method in order to achieve extra energy savings. In this paper, we propose an artificial intelligence based real-time optimal control method that minimizes electricity consumption and assures safe operation simultaneously. The main idea of our proposed method is to evolutionary search the optimal range of controlled variable during a normally operative condition. Furthermore, an optimal operating condition can be achieved without requiring large-scale data to learn a model. Experimental results demonstrate that indoor temperature of a data center can be constantly controlled safely and cost effectively based on our proposed methodology.

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A Study on the Development of Flattening Process for Burr Removal and Product Evaluation: Choon-Man Lee, Jong-Sup Lim, Seong-Gyu Kim, Sung-Woo Shin; J. Korean Soc. Precis. Eng. 2021;38(3):163-168.
Published online March 1, 2021; DOI: https://doi.org/10.7736/JKSPE.020.097

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The plate for the multi-stage reducer is a component of a traveling motor and is required for high wear resistance and maintaining precision. The plates that are mainly manufactured by the press process have burrs on the edges of the material after the general press shear process. Since burrs have a great influence on assembly and shape precision according to product characteristics, a post-treatment process for removing burrs is mandatory, and several studies have been conducted on this topic. In this study, a flattening process was developed to remove the burrs. First, the piercing and blanking process forming analysis was performed to find the process conditions for burr removal. Subsequently, the flattening process forming analysis was performed, and the reliability of the analysis was verified through an experiment using the derived process conditions.

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Reliable Replication Molding Process for Robust Mushroom-Shaped Microstructures: Joon Hyung An, Ji Seong Choi, Seong Min Kang; J. Korean Soc. Precis. Eng. 2020;37(11):855-860.
Published online November 1, 2020; DOI: https://doi.org/10.7736/JKSPE.020.062

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In this paper, we present a simple and robust fabrication method for mushroom-shaped microstructures using diverse polymers with various modulus of elasticity. Through the repeated replica molding process, we fabricated the same PDMS mushroom structure negative mold as the prepared silicon master mold. To evaluate the fabricating stability of the fabricated PDMS negative mold, the mushroom-shaped structures were replicated from the mold using six types of polymer resins with different elastic modulus and we measured superhydrophobic properties on the samples. All the fabricated samples exhibited superhydrophobicity, and we proved the structural stability of the proposed replication method through the measured SEM images, contact angles on the samples, and theoretical analysis based on the structural shape.

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Mastering of NIL Stamps with Undercut T-Shaped Features from Single Layer to Multilayer Stamps
Philipp Taus, Adrian Prinz, Heinz D. Wanzenboeck, Patrick Schuller, Anton Tsenov, Markus Schinnerl, Mostafa M. Shawrav, Michael Haslinger, Michael Muehlberger
Nanomaterials.2021; 11(4): 956. CrossRef

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Analysis of Effect of Stirring Process Conditions on Liquid Viscosity in an Overhead Stirrer: Ho Cheol Lee, Gi Dae Kim; J. Korean Soc. Precis. Eng. 2020;37(9):659-665.
Published online September 1, 2020; DOI: https://doi.org/10.7736/JKSPE.020.033

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To monitor the stirring state by on-line estimation of liquid viscosity instead of stopping the stirring process and measuring the viscosity using viscometer, a basic study clarifying the effect of stirring conditions was carried out. For this purpose, the relationship between liquid viscosity and the stirring conditions, such as stirring torque, stirring speed, the duty ratio of PWM, impeller and beaker type, and the blade position in the beaker was analyzed. The second-order relationship between the stirring speed and torque, the linear relationship between viscosity and torque, and the linear relationship between duty ratio of PWM and stirring speed were observed, thereby indicating that the liquid viscosity could be estimated by an experimental formula based on the duty ratio and the stirring speed. In addition, the type of impeller and beaker was identified using the magnetic field inside impeller and RFID technology. For reducing the error in calculating the liquid viscosity, the employment of an impeller blade with a large rotational resistance and stirring with the blade at the center zone of the beaker were found to be necessary.

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A Study on Contactless Identification of Impellers Using a Digital Hall Sensor
Ho-Cheol Lee
Journal of the Korean Society of Manufacturing Process Engineers.2021; 20(12): 71. CrossRef

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Development of Snow Melter with Horizontally Located Burner: Jang Yong Lee, Byung Yeol Bang, Hye Seong Kim, Gye Seok Lee, Soon Ha Ser, Sam Ho Im; J. Korean Soc. Precis. Eng. 2020;37(2):115-123.
Published online February 1, 2020; DOI: https://doi.org/10.7736/JKSPE.019.067

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Snow removal equipment in Korea has been developed to remove snow from roads by pushing it away with snow shovels or dispersing it into the air with snow blowers. However, in urban areas, it is difficult to use snow blowers. And piled snow on sidewalks not only hinder pedestrians from walking by, but also melt onto the roads during the day and freeze at night, causing traffic accidents. As a solution to this, there has been a need to develop a machine which melts snow on the place where high priority is given for snow clearing such as airports, roads of frequent black ice occurrence, and main traffic facilities. This paper describes the main design points and experimental results in developing the snow melting system composed of the burner, blower, water tank, etc. Hot air from the burner spouts into the water tank and some of it rises through the outer jacket where hot air is mixed with water in the tank, heating it. Hot air spouted to the bottom of water tank and hot water pouring from the head of the outer jacket are two sources of snow melting in designing the equipment.

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Study on Thermal Efficiency and Heat Transfer Analysis due to the Application of Snowmelting Deck of Carbon Fiber Heating Wire
Jeong-Keun Kim, Hong-Gun Kim, Hee-Jun Eun, Lee-Ku Kwac
Journal of the Korean Society of Manufacturing Process Engineers.2023; 22(2): 39. CrossRef

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Digitalization of Analog Magnetic Field Signals for Automatic Discriminating Impeller Types of an Overhead Stirrer: Ho Cheol Lee, Myeong Su Kang, Gi Dae Kim; J. Korean Soc. Precis. Eng. 2019;36(11):1033-1038.
Published online November 1, 2019; DOI: https://doi.org/10.7736/KSPE.2019.36.11.1033

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To identify the impeller types automatically for an overhead stirrer operation, a digitalization of the analog magnetic signal of the permanent magnet arrays was performed. The permanent magnets were installed into the impeller shaft in NS-SN array, and their magnetic fields were measured by a hall sensor while the impeller was mounted on the stirrer. Results of the experiments and finite element analysis showed that the number of peaks of magnetic field signal was observed corresponding to the number of magnets. Considering the consistency of the number and the magnitude of magnetic field peaks, it was found to be more advantageous to measure the magnetic field in the axial than in the radial direction of the impeller. For eliminating the influence of the noise included in the analog signal and connecting it with the micro-controller of the stirrer, the analog magnetic field signal was transformed to the digital-pulse-patterned signal through DC offset, amplification, absolute value, and the comparator circuit. Through these processes, the error in identifying the impeller type could be significantly reduced compared with directly using the magnitude of the analog magnetic signal.

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A Study on Contactless Identification of Impellers Using a Digital Hall Sensor
Ho-Cheol Lee
Journal of the Korean Society of Manufacturing Process Engineers.2021; 20(12): 71. CrossRef
Analysis of Effect of Stirring Process Conditions on Liquid Viscosity in an Overhead Stirrer
Ho Cheol Lee, Gi Dae Kim
Journal of the Korean Society for Precision Engineering.2020; 37(9): 659. CrossRef

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