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.
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.
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
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.
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
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
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.
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.
The mechanical drilling of micro holes is considered a difficult endeavor, due to the high hardness and brittleness of alumina plates found during the drilling process. In this work, an alumina plate with a 4mm thickness is drilled with the use of a continuous-wave Nd:YAG fiber laser. As can be seen, there is minimum required power density to ablate the alumina plate. As shown in this study, the hole diameter and straightness are not constant with the hole depth recorded, which is presumably due to the recondensation of vaporized alumina, and the characteristics of irregular laser radiation. The oxygen pressure, power density, focal position, and laser on time (duration) are chosen as the control parameters. To understand the influence of control parameters, the orthogonal arrays table in Taguchi method is applied, and the micro holes are evaluated based on the use of geometrical factors. Through the review of a sensitivity and interaction analysis, the appropriate duration and oxygen pressure are identified as the major parameters governing the geometrical quality of drilled holes in this study.
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Micro Drilling of Single Crystal SiC Using Polycrystalline Diamond Tool Ui Seok Lee, Chan Young Yang, Ju Hyeon Lee, Bo Hyun Kim Journal of the Korean Society for Precision Engineering.2021; 38(7): 471. CrossRef
Micro hole drilling in precision production industries requires smaller holes, higher aspect ratios, and higher working speeds. However, the undesirable characteristics of micro drilling are small signal to noise ratios, wandering drill motion, high aspect ratio, and increasing cutting quality as cutting depth increases. In this study, two different types of experiments are performed on single crystal silicon to decrease crack formation. The first experiment compares the efficiency of various micro hole machining processes using ultrasonic impact grinding and micro drilling. The second experiment suggests optimum conditions for the micro drilling process. The experimental results show that micro drilling technology can be effectively used for drilling single crystal silicon.
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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 Noh Journal of the Korean Society for Precision Engineering.2025; 42(2): 139. CrossRef
Micro Drilling of Single Crystal SiC Using Polycrystalline Diamond Tool Ui Seok Lee, Chan Young Yang, Ju Hyeon Lee, Bo Hyun Kim Journal of the Korean Society for Precision Engineering.2021; 38(7): 471. CrossRef
Fabrication of Micro Tool Electrode by Micro EDM using Wear Ratio In Yong Moona, Do Kwan Chung, Bo Hyun Kim Journal of the Korean Society of Manufacturing Technology Engineers.2018; 27(1): 1. CrossRef
The recent development of core techniques in the IT industry can be summarized as a technical advancement for safety and convenience, and mechanical technology for being “eco-friendly” and lightweight. Under these circumstances, research of lightweight material has become attractive. In this study, CFRP (Carbon Fiber Reinforced Plastic) laminate specimens are subjected to a tensile test using the UTM(Universal Testing Machine, AG-IS 100 kN) to estimate their mechanical properties in terms of the Hole machining impact evaluation. The FEM (Finite Elements Method) analysis method is applied and the material properties obtained from basic experiments such as the Tensile test, the compressive test, and the shear test. CFRP materials properties from a previous study, as well as a finite element analysis program for Hole machining CFRP was compared with the experiments.
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Comparative Study on J-Integrals of SM45C, Short Fiber GFRP and Woven Type CFRP Shown at Crack through Analytical Method Jae Woong Park, Sung Ki Lyu, Jae Ung Cho Journal of the Korean Society for Precision Engineering.2019; 36(6): 567. CrossRef
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