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.
In the optical systems field, key components such as spectroscopic elements often require the use of optical materials with high-refractive indices to achieve miniaturization and lightweight characteristics. However, high-refractive index optical materials have low machinability due to their brittle characteristic. In this study, we investigated the changes in surface characteristics during precision pattern machining of high-refractive index materials; specifically, a low fracture toughness, for use in grating spectroscopic elements. The experiment involved diamond turning for the primary machining, and for the secondary pattern machining, the tool rake angle, tool feed rate, and depth of cut were set as variable conditions. Surface roughness measurements and surface quality analyses were carried out using a white-light interferometer and tool microscopy. The results provide insights into the influence of conditions on the surface properties during the machining of high-refractive index materials for grating spectroscopic components. Under the machining conditions with a tool rake angle of -65o, tool feed rate of 5,000 mm/min, and a depth of cut 10 nm, the surface roughness of Ra 8.0 nm was achieved. Based on these findings, we plan to conduct further research on the mechanical fabrication of the blaze angle for grating spectroscopic components.
Advanced engineering ceramics have been highlighted mainly owing to their superior hardness, corrosion/wear resistance, and thermal insulation performances. However, they are usually very difficult-to-cut because of their high brittleness. In light of this, ultra-precision machining has been studied to perform ductile-regime cutting in the machining of ceramics. Ductile-regime cutting can feature a smoother surface, and lower subsurface damage as the dominant material response during cutting showed ductile behavior. Researchers have investigated promoting ductileregime cutting to improve the machinability of ceramics. In this study, various coating materials were applied to the workpiece surface, and their effects on machinability improvements were explored. A total of 6 surface coatings and lubricants were applied to soda-lime glass. The critical depth of cut (CDC), the depth where the ductile-brittle transition (DBT) occurred, was increased in all coatings and lubricants, with an improved ductile cutting regime. Experimental results showed that solid coatings were more effective than liquid lubricants in enhancing the ductile cutting regime. It was thought that solid coatings induced an additional downward force by resisting material deformation and chip evacuation, thus contributing to suppression of crack opening. It is expected that this research can contribute to the machinability improvements of brittle materials.
Germanium, an optical material, has high transmittance and refractive index and low light scattering in the infrared region, and research is being conducted to utilize it in various industrial fields. Various forms of optical lenses can be subjected to ultra-precision machining with high quality surface roughness, and they form accuracy through single point diamond turning (SPDT). In particular, the diamond tool with a negative rake angle and the u-LAM process that applies a 1,064 nm laser to the material have been studied to fabricate brittle materials into optical lenses. In this study, the effects of process parameters, such as laser power (W), spindle speed (RPM), feed rate (mm/min), and depth of cut (μm), on the surface roughness of a sub-nanometer scale and the occurrence of defects during the machining process were analyzed for Germanium materials. The process of removing these defects was also analyzed.
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A Study on Pattern Machining Technology for Germanium Materials Using Grooving Machining Process Joong Kyu Ham, Jong Gyun Kang, Hwan Ho Maeng, Seong Hyeon Park, Jin Yong Heo, Young Durk Park, Geon Hee Kim Journal of the Korean Society for Precision Engineering.2024; 41(2): 111. CrossRef
Fabrication and Characterization of Automotive Aspheric Camera Lens Mold based on Ultra-precision Diamond Turning Process Ji-Young Jeong, Hwan-Jin Choi, Jong Sung Park, Jong-Keun Sim, Young-Jae Kim, Eun-Ji Gwak, Doo-Sun Choi, Tae-Jin Je, Jun Sae Han Journal of the Korean Society for Precision Engineering.2024; 41(2): 101. CrossRef
Computer numerical control (CNC) part programs generated by computer-aided manufacturing software are frequently composed of numerous G01 blocks. CNC interpolator applies acceleration and deceleration to generate velocity profile of each block. Therefore, the machining time is increased when the number of G01 blocks is increased. To reduce the machining time, corner blending has been used to smooth the corner shape of adjacent blocks. Because the tool path generated by corner bending dose not reach the commanded endpoint, error of the interpolated tool path exists. The objective of this study was to present a method to determine block overlap time to limit tool path error generated by corner blending. An algorithm to calculate tool path error with respect to block overlap time was also proposed. Performance of the proposed algorithm to limit tool path error was demonstrated in this study.
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Impact of broad ion beam center alignment and mask position on Si wafer cross-section milling rate Jong-Han Won, Ki-Hwan Kim, Dong-Young Jang, Geon-Yeong Park Micro & Nano Manufacturing.2025;[Epub] CrossRef
Block Overlap Based CNC Interpolator with Variable Time Constant Chan-Young Lee, Chang-Ju Kim, Seung Guk Baek, Segon Heo Journal of the Korean Society for Precision Engineering.2025; 42(2): 169. CrossRef
Process Monitoring and Part Program Optimization Using Virtual Machine Tools Chang-Ju Kim, Segon Heo, Chan-Young Lee, Jung Seok Oh Journal of the Korean Society for Precision Engineering.2022; 39(12): 879. CrossRef
Cycle Time Estimation of Block Overlap Based CNC Chan-Young Lee, Seung-Kook Ro, Chang Kyu Song, Jeong Seok Oh Journal of the Korean Society for Precision Engineering.2022; 39(7): 537. CrossRef
Improved Input Shaping Method for Circular Interpolation of a 2-Axis Positioning System Jin Uk Sim, Pil Kyu Choi, Sun-Woong Kwon, Seong-Wook Hong Journal of the Korean Society for Precision Engineering.2022; 39(4): 283. CrossRef
CNC Algorithms for Precision Machining: State of the Art Review Chan-Young Lee, Seong Hyeon Kim, Tae In Ha, Jaehong Min, Soon-Hong Hwang, Byung-Kwon Min Journal of the Korean Society for Precision Engineering.2018; 35(3): 279. CrossRef
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