Journal of the Korean Society for Precision Engineering

A Study on the Detection of Hole in Automotive CV Joint Boot Using Image Processing and AI Techniques: Yun-Hyeok Lim, Hyeongill Lee; J. Korean Soc. Precis. Eng. 2025;42(10):861-869.
Published online October 1, 2025; DOI: https://doi.org/10.7736/JKSPE.025.050

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Detecting and analyzing defects in components or systems is crucial for maintaining high-quality standards in modern manufacturing and quality control. Recently, imaging-based defect detection methods have gained popularity across various engineering fields, highlighting their growing importance. Additionally, the integration of Artificial Intelligence (AI) to improve accuracy and efficiency is rapidly advancing. This paper presents a system that uses imaging to detect holes in CV joint boots, as these holes significantly affect the overall performance and durability of the system. Moreover, it introduces a method for enhancing detection performance by applying AI techniques. Validation tests on actual CV joint boots confirmed that the proposed method improves detection performance.

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Pinhole Detection in Thin Film Solid Oxide Electrolytes Using Selective Adsorption of Ag Nanoparticles via a Spark Discharge Generator: Doyoon Kim, Ikwhang Chang, Jong Dae Baek; J. Korean Soc. Precis. Eng. 2025;42(6):441-446.
Published online June 1, 2025; DOI: https://doi.org/10.7736/JKSPE.025.024

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Pinhole-free ionic conductors are critical to achieve optimal performance in thin film-solid oxide fuel cells (TF-SOFCs). However, nanoscale defects, especially pinholes, can induce current leakage and contribute to cell failure by creating electrical short circuits. This study introduced a novel methodology for detecting pinholes in yttria-stabilized zirconia (YSZ) thin-film solid oxide electrolytes. The approach utilized selective adsorption of silver (Ag) nanoparticles generated via a spark discharge generator (SDG). Analytical techniques, including focused ion beam (FIB), scanning electron microscopy (SEM), and transmission electron microscopy (TEM), were employed to investigate interactions between Ag nanoparticles and nanoscale defects. Results showed that nanoparticle-based diagnostic methods were efficacious for defect characterization, offering a solution for enhancing the quality of thin-film electrolytes.

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Micro Hole Machining Characteristics of Glassy Carbon Using Electrical Discharge Machining (EDM): Jae Yeon Kim, Ji Hyo Lee, Bo Hyun Kim; J. Korean Soc. Precis. Eng. 2025;42(4):325-332.
Published online April 1, 2025; DOI: https://doi.org/10.7736/JKSPE.025.006

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Glassy carbon (GC) has superior properties such as high corrosion resistance, heat resistance, and low adhesion to glass materials in a glass molding process (GMP). In addition, the demand for GC molds is increasing in various industries that require high precision of glass parts. However, GC is a difficult-to-machine material with high hardness and brittleness. Electrical discharge machining (EDM) can machine GC regardless of its strength or hardness. In this study, tungsten carbide (WC-Co) electrode was fabricated by wire electrical discharge grinding (WEDG). Characteristics of EDM of micro holes on GC were then analyzed. As capacitance and voltage increased, material removal rate (MRR) increased while machining time tended to decrease. However, at low voltages, short circuit and secondary discharge occurred, which increased the electrode wear rate (EWR). As a result, a D-shaped electrode that could prevent short circuit and debris accumulation was fabricated and a micro hole array was machined.

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Numerical Study on Design Approaches for Reduction of Float and Elimination of Over-constraints in Hole-pin Pattern Assembly: Jung Hun Lee, Hyunjune Yim; J. Korean Soc. Precis. Eng. 2025;42(2):147-156.
Published online February 1, 2025; DOI: https://doi.org/10.7736/JKSPE.024.121

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This paper addresses the issue of over-constrained assembly in mechanical designs using hole-pin patterns. When two hole-pin pairs are used, they can cause interference between components, leading to assembly failures. To mitigate this, designers often enlarge holes relative to pins to have a large float. However, when functional requirements do not permit significant float, field design engineers tend to add more assembly features, hoping them to mutually limit the float allowed by others. This numerical study employed two commercial tolerance analysis programs to demonstrate that these design changes could not sufficiently reduce float to justify added costs. Instead, this paper proposed an exactly-constrained design by replacing one of the holes with an elongated hole. Numerical analysis showed that this approach significantly reduced float compared to current design practices. This paper logically explains why this must be the case. It is hoped that this study contributes to the advancement of mechanical assembly design practices by adopting the exact constraint concep.

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Large-area Inspection Method for Machined Micro Hole Dimension Measurement Using Deep Learning in Silicon Cathodes: Jonghyeok Chae, Dongkyu Lee, Seunghun Oh, Yoojeong No; J. Korean Soc. Precis. Eng. 2025;42(2):139-145.
Published online February 1, 2025; DOI: https://doi.org/10.7736/JKSPE.024.117

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In this study, we propose a deep learning-based method for large-area inspection aimed at the high-speed detection of micro hole diameters. Micro holes are detected and stored in large images using YOLOv8, an object detection model. A super-resolution technique utilizing ESRGAN, an adversarial neural network, is applied to images of small micro holes, enhancing them to high resolution before measuring their diameters through image processing. When comparing the diameters measured after 8x super-resolution with the results from existing inspection equipment, the average error rate is remarkably low at 0.504%. The time taken to measure an image of one micro hole is 0.470 seconds, which is ten times faster than previous inspection methods. These results can significantly contribute to high-speed measurement and quality improvement through deep learning.

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A Review of Intelligent Machining Process in CNC Machine Tool Systems
Joo Sung Yoon, Il-ha Park, Dong Yoon Lee
International Journal of Precision Engineering and Manufacturing.2025; 26(9): 2243. CrossRef

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Selection of Optimal Condition for Reducing Dimensional Error of Holes in Dry Cutting of Polyacetal Resin with Indexible Drill: Seho Chun; J. Korean Soc. Precis. Eng. 2024;41(6):429-434.
Published online June 1, 2024; DOI: https://doi.org/10.7736/JKSPE.024.006

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In this study, polyacetal plates were machined with an indexable drill (Ø18mm) to measure the dimensional error of holes according to the cutting conditions and investigate the influencing factors to obtain precision holes. Cutting velocity, feed, and depth of cut were selected as experimental variables, analyzed using design of experiment, and optimal cutting conditions were investigated. Cutting velocity and feed were significant factors affecting hole accuracy, whereas depth of cut had little effect. The factor with the greatest influence on hole accuracy was cutting velocity, and the dimensional error of the holes tended to increase as the cutting velocity increased. Dimensional error tended to decrease as feed increased. In addition, the interaction effect between cutting velocity and feed and cutting velocity and depth of cut were significant. In this experiment, the optimal cutting velocity, feed, and depth of cut needed to minimize the dimensional error of holes were 100 m/min, 0.15 mm/rev, and 2 mm, respectively.

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Improving Micro-hole Laser Drilling Performance Using an AOM: Young Hoon Kim, Sang Hwan Choi, Se Kyung Chun, Ji Won Lee, Doo Hyun Cho, Myung Woon Kim; J. Korean Soc. Precis. Eng. 2024;41(6):423-428.
Published online June 1, 2024; DOI: https://doi.org/10.7736/JKSPE.024.005

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PCBs (Printed circuit boards) have been widely used in electronic products such as wearables, smartphones, and table computers. Recent trends of miniaturizing electric components require improvement of component density and electronic functionality by decreasing the size of micro via holes (50-110 μm), which interconnect electric signals between adjacent layers in high density interconnection (HDI) PCBs. To generate micro via holes, we studied CO₂ laser drilling with the help of pulse shape controlling using acousto-optic modulator (AOM). Pulse shape controlling is one of the key factors to reduce heat effect during the laser drilling process. To increase laser absorption, the substrate was subjected to black oxidation prior to CO₂ laser drilling. We designed a diffractive optical system using a circular aperture. Micro via holes were obtained by optimizing the optical distance. The laser drilled via hole was studied both experimentally and theoretically.

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Machining Characteristics of Micro EDM of Silicon Carbide: Ju Hyeon Lee, Chan Young Yang, Bo Hyun Kim; J. Korean Soc. Precis. Eng. 2024;41(2):131-137.
Published online February 1, 2024; DOI: https://doi.org/10.7736/JKSPE.023.137

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Silicon carbide (SiC) is chemically stable, highly heat-resistant, and resistant to thermal shock. SiC having excellent characteristics in a high temperature and high voltage environment is used in high-power semiconductors, highprecision mechanical devices, optical components, etc. As it is used in various industries, there is a growing demand for processing fine holes or grooves in silicon carbide. In this study, micro holes and grooves were machined on 4HSiC and sintered SiC using electrical discharge machining (EDM). Silicon carbide which has very high hardness can be easily processed by EDM as compared with mechanical processes. As a tool material, a polycrystalline diamond (PCD) which has high wear resistance was used and a micro tool of a diameter of 100 μm was fabricated by wire electrical discharge grinding (WEDG). In the EDM of SiC, the machining characteristics such as surface roughness, discharge gap, and tool wear were investigated.

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Micro Hole Machining Characteristics of Glassy Carbon Using Electrical Discharge Machining (EDM)
Jae Yeon Kim, Ji Hyo Lee, Bo Hyun Kim
Journal of the Korean Society for Precision Engineering.2025; 42(4): 325. CrossRef
Prediction of Machining Conditions from EDMed Surface Using CNN
Ji Hyo Lee, Jae Yeon Kim, Dae Bo Sim, Bo Hyun Kim
Journal of the Korean Society for Precision Engineering.2024; 41(11): 865. CrossRef

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Development of Vision System for Quality Inspection of Machined Holes of Automobile Mechanical Parts: Min Yong Han, Ki Hyun Kim, Hyo Young Kim, Kwang In Ko, Kyo Mun Ku, Dong Ju Ki, Jae Hong Shim; J. Korean Soc. Precis. Eng. 2023;40(6):499-506.
Published online June 1, 2023; DOI: https://doi.org/10.7736/JKSPE.022.141

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This paper presents a vision system for machined hole quality inspection of mechanical parts in an automobile. Automobile parts have various shapes and holes created by press punches. However, if the press punch pin is broken, a hole is not created on the mechanical parts. This problem causes serious part quality defects. To solve this problem, we proposed a vision system that could easily and cheaply inspect the quality of holes in automotive machining parts. A software development environment was created to build an economical vision inspection system. Images were gathered using the Near-real-time method to overcome the low frame-per-second of inexpensive Complementary Metal Oxide Semiconductor (CMOS) webcams. Status of the hole was determined using template matching and distance between holes as a feature. The hardware required for vision inspection was designed so that it could be directly applied to the automotive part manufacturing process. When the proposed vision inspection system was tested by installing it in an automobile parts factory for 3 months, the system showed an inspection accuracy of at least 97.9%. This demonstrates the effectiveness of the proposed method with accuracy and speed of hole defect inspection of machined parts.

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A Numerical Investigation of Heat Transfer Characteristics with Varying Film Cooling Hole Shapes for Gas Turbine Blade Cooling: Chan Hyeok Park, Sajan Tamang, Hwabhin Kwon, Jaemun Choi, Heesung Park; J. Korean Soc. Precis. Eng. 2022;39(6):443-450.
Published online June 1, 2022; DOI: https://doi.org/10.7736/JKSPE.022.018

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Recently, film cooling has been continuously studied to increase the efficiency of gas turbines. A turbine inlet temperature increase occurs as a way to improve the efficiency. However, it is essential to improve the cooling performance of the blade surface because of the melting point of the part. In this paper, a side hole shape wherein a general cylinder hole and two auxiliary holes are combined, is proposed to improve the film cooling efficiency, and the blowing ratio was set to 0.4, 0.8, 1.2, and 2.0. When side hole was applied, the vortex interference at the hole entrance occurred less than that of the cylinder hole. That is, the flow rate of the coolant adsorbed to the surface increased to improve the cooling performance. In conclusion, compared to the cylinder hole, the cooling efficiency of the shape to which the side hole was applied was excellent, and in particular, the average area cooling efficiency with spanwisely designed side holes improved by 83%.

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Melting Depth Characteristics according to Electron Beam Dose for Electron Beam Micro-Hole Drilling: Joon-Goo Kang, Byung-Kwon Min, Eun Goo Kang; J. Korean Soc. Precis. Eng. 2021;38(3):169-176.
Published online March 1, 2021; DOI: https://doi.org/10.7736/JKSPE.020.104

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E-Beam micro-hole drilling features high productivity of 2,000 holes per second and a high aspect ratio of 10 (depth/diameter). It can be used for the fabrication of nozzles and filters that require several holes. The hole-formation mechanism comprises 1) melting the sample by the energy exchange of e-beam and 2) removing the molten sample by the explosion of the backing material. Accordingly, hole-formation mechanism studies have focused on the effectiveness of backing material and the workpiece’s melting characteristic. This study investigated the melting depth characteristics depending on the beam current and exposure time that determines the E-Beam dose. The experiments were conducted without using the backing materials with an aim to investigate the melting characteristic of the workpiece itself. The results showed that the increase in the exposure current led to an improvement in the melting depth. The results were verified based on the comparison with the results of the process involving the backing material.

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Micro CT Analysis of Microholes Drilled by Focused Electron Beam Drilling Based on Image Noise Reduction Using Masking Layers
Hyunmin Park, Joon-Goo Kang, Jin-Seok Kim, Eun Goo Kang, Hyung Wook Park, Jaewoo Seo
Journal of the Korean Society of Manufacturing Technology Engineers.2022; 31(6): 388. 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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Micro Machining of CFRP Using Nanosecond Pulsed Fiber Laser: Do Kwan Chung, Jin Sung Park, Ki Hun Kim; J. Korean Soc. Precis. Eng. 2019;36(9):783-791.
Published online September 1, 2019; DOI: https://doi.org/10.7736/KSPE.2019.36.9.783

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CFRP (Carbon fiber reinforced plastic) has been widely used in different industries such as aerospace, automobile, sports and medical. Laser processing of CFRP has a great potential for industrial applications. In this paper researched the micro cutting and drilling of CFRP with 0.5 mm thickness using 1064 nm ytterbium nanosecond pulsed fiber laser. It also investigated machining characteristics of micro cutting and drilling according to laser power, frequency, scan speed and number of scan (or irradiation). Complete cutting and through-hole drilling were achieved with low frequency when the laser power was low and with low and middle frequency when the laser power increased. However, those were not achieved a frequency of 100 kHz. The cutting width increased when the power increased and decreased when the frequency and the scan speed increased. The hole size increased when the power and the number of irradiation increased and decreased when the frequency increased. In the case of micro hole array, the hole was blocked during the next hole machining when the hole spacing was narrow. The resin was melted by the heat thus blocking the pre-drilled hole. We devised the laser scan method, and the micro hole array with narrow hole spacing was fabricated successfully.

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Laser Drilling of Micro-Hole Array on CFRP Using Nanosecond Pulsed Fiber Laser
Do Kwan Chung
Journal of the Korean Society of Manufacturing Process Engineers.2024; 23(5): 92. CrossRef
Laser EDM Hybrid Micro Machining of CFRP
Do Kwan Chung, Chan Ho Han, Yu Jin Choi, Jun Seo Park
Journal of the Korean Society for Precision Engineering.2023; 40(2): 99. CrossRef
Micro Pin Fabrication of Tungsten Carbide Using Polycrystalline Diamond
Joo A Park, Ui Seok Lee, Bo Hyun Kim
Journal of the Korean Society for Precision Engineering.2020; 37(11): 791. CrossRef

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A Study on the Strength Characteristic of Compact Tension Specimen due to Internal Holes and Material: Jung-Ho Lee, Sung-Ki Lyu, Jae-Ung Cho; J. Korean Soc. Precis. Eng. 2019;36(7):623-629.
Published online July 1, 2019; DOI: https://doi.org/10.7736/KSPE.2019.36.7.623

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Majority of deformation and ruptures as a result of severe deformation of mechanical structures are due to the existence of cracks or cracks generated through specific situations. These cracks causes stress concentration and eventually ruptures under lower load conditions than they are designed to withstand. In this study, simulation tensile analysis was done by designing compact tension specimen models with the number of holes that existed inside and the materials of the test specimens by focusing on the effects of the cracks. The study results from all the analysis (deformations, equivalent stress and strain energy) confirmed that the specimen models having two holes had better strength characteristics than those with only one hole. Additionally, the durability and strength characteristics of specific mechanical structures against the load improved through appropriate arrangement of holes thereby reducing stress generation. As such the results of this study could be utilized as the basic data for future researches on composite materials and sandwich type homogenous materials. Furthermore, the study results can assist in designing more durable products.

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Study on the Deburring of Intersecting Holes with Abrasive Flow Machining: Joon Kyu Beom, Young Gwan Kim, Kwang Joon Kim, Kwon Hee Kim; J. Korean Soc. Precis. Eng. 2019;36(2):163-168.
Published online February 1, 2019; DOI: https://doi.org/10.7736/KSPE.2019.36.2.163

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Intersecting holes deep inside a workpiece, are difficult to deburr because of poor accessibility. When holes are small and the intersecting angle (acute angle between hole axes) is less than 45°, difficulty is at its extreme. In this study, abrasive flow machining is used for a hole diameter of 3mm and intersecting angles of 30° and 45°. Tests were performed for AL6061 specimens, with process parameters allocated to L8(2⁷) orthogonal array. Degree of deburring is strongly dependent on intersecting angle, abrasive grit size, and total volume of flow. Successful deburring was achieved for 30° intersecting angle.

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