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JKSPE : Journal of the Korean Society for Precision Engineering

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"Jong Wan Ko"

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"Jong Wan Ko"

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Microwave-induced Enhancement of Interlayer Strength in FDM-printed Nylon6/Carbon Fiber Composites
Si Woo Kim, Ho Geun Nam, Jong Wan Ko
J. Korean Soc. Precis. Eng. 2026;43(5):517-526.
Published online May 1, 2026
DOI: https://doi.org/10.7736/JKSPE.025.112
Among 3D printing techniques, fused deposition modeling (FDM) is known for its design flexibility, rapid fabrication, and the ability to produce complex geometries without molds. However, weak interlayer adhesion often results in poor mechanical strength along the build (Z) direction, limiting its use in structural applications. Instead of altering printing parameters or switching technologies, we propose a simple microwave-irradiation post-treatment to enhance interlayer bonding in FDM-printed parts. By optimizing microwave power and exposure time, we significantly improved interlayer fusion while maintaining the original geometry. Cross-sectional microscopy before and after treatment confirmed markedly improved interlayer bonding (Unbonded interfacial area fraction: 56.82% → 15.51%; -41.31 percentage points, -72.7%). Correspondingly, the Z-direction tensile strength increased from 42.38 to 49.11 MPa (+6.73 MPa, +15.9%). This straightforward post-processing method effectively addresses a key limitation of FDM, thereby expanding its potential for structural and industrial applications.
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Article
Optimization of Angle of Incidence of the Laser Beam in Laser-FIB Hybrid Processing and Design of an Integrated System
Jeonghong Ha, Kyu Song, Hyun Choi, Chung-Soo Kim, Jong Wan Ko, Dong-Young Jang
J. Korean Soc. Precis. Eng. 2025;42(7):529-536.
Published online July 1, 2025
DOI: https://doi.org/10.7736/JKSPE.025.063
The need for large-area cross-sectional analysis with nanometer precision is rapidly growing in various advanced manufacturing sectors. Traditional focused ion beam (FIB) techniques are too slow for milling millimeter-scale volumes. They often introduce ion implantation, redeposition, and curtaining effect, which ultimately prevent effective large-area processing and analysis. To overcome these limitations, we developed a hybrid machining process integrating femtosecond laser micromachining for rapid roughing with FIB milling for precision finishing. Angle of incidence (AOI) control during laser machining was employed to minimize the taper angle of laser-ablated sidewalls, thereby significantly reducing subsequent FIB milling volume. Using a 1030 nm, 350 fs laser, we achieved nearly vertical sidewalls (taper angle: ~2.5° vs. ~28° without AOI control) in silicon. Raman spectroscopy revealed a laser-affected zone extending about 2 μm perpendicular to the sidewall, indicating the need for further FIB milling besides laser-tapered regions to remove laser-induced damage. On multilayer ceramic capacitors and micropillar fabrication, the hybrid laser-FIB method achieved efficient large-area cross sections with preserved microscale details. We present the development of an integrated triple-beam system combining laser, plasma FIB, and SEM, capable of fast volume removal and nanoscale imaging in one equipment. This approach can markedly improve throughput for large-area cross-sectional analysis.
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