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
As the digitization of the manufacturing process is accelerating, various data-driven approaches using machine learning are being developed in chemical mechanical polishing (CMP). For a more accurate prediction in contact-based CMP, it is necessary to consider the real-time changing pad surface roughness during polishing. Changes in pad surface roughness result in non-uniformity of the real contact pressure and friction applied to the wafer, which are the main causes of material removal rate variation. In this paper, we predicted the material removal rate based on pressure and surface roughness using a deep neural network (DNN). Reduced peak height (Rpk) and real contact area (RCA) were chosen as the key parameters indicative of the surface roughness of the pad, and 220 data were collected along with the process pressure. The collected data were normalized and separated in a 3 : 1 : 1 ratio to improve the predictive performance of the DNN model. The hyperparameters of the DNN model were optimized through random search techniques and 5 cross-validations. The optimized DNN model predicted the material removal rate with high accuracy in ex-situ CMP. This study is expected to be utilized in data-driven machine learning decision making for cyber-physical CMP systems in the future.
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Precision Engineering and Intelligent Technologies for Predictable CMP Somin Shin, Hyun Jun Ryu, Sanha Kim, Haedo Jeong, Hyunseop Lee International Journal of Precision Engineering and Manufacturing.2025; 26(9): 2121. CrossRef
Prediction of Normalized Material Removal Rate Profile Based on Deep Neural Network in Five-Zone Carrier Head CMP System Yonsang Cho, Myeongjun Kim, Munyoung Hong, Joocheol Han, Hong Jin Kim, Hyunki Kim, Hyunseop Lee International Journal of Precision Engineering and Manufacturing-Green Technology.2025; 12(3): 869. CrossRef
With the development of 3D printing technology, its applications are expanding. However, 3D printed parts present a challenge in achieving high-quality surface roughness because of stair stepping problems. With the recent application of 3D printing in electronics and the visibility of flow in microfluidic systems, high-quality surface roughness is needed. Chemical mechanical polishing (CMP), one of semiconductor fabrication processes, has the longest planarization length in terms of productivity among existing planarization methods. In this study, we investigate friction characteristics of polishing of ABSLike resin material printed by the Stereolithography Apparatus (SLA). At the polishing of ABS-Like resin, the friction force has a high value at the beginning of polishing, but it stabilizes as processing progresses because of the effect of waviness on the printed material. The surface roughness (Sa and Sz) reduction and the glossiness of ABS-Like resins after polishing appear to be related to the reduction of the Shore D hardness resulting from the rise in the polishing process temperature caused by friction during polishing.
Carbon Fiber Reinforced Plastic (CFRP) materials which are superlight in weight and have high strength have recently been applied in the automobile and aerospace industry, etc. to achieve high fuel efficiency. CFRP is termed as ‘difficult to cut material’ due to its unique material properties. It’s considered to be highly sensitive in processing due to its laminated structure which would pose some challenges such as delamination, Pull-out, Burr and Uncut. Due to this, it’s maintenance and treatment costs are high. There are also limitations in the conventional Gantry Machine in 3D shape cutting of CFRP materials. To counter this challenge, a robotic abrasive waterjet system with the following features has been developed and installed on site; a high-pressure pump, monitoring system and a catcher for 3D Shape cutting., It’s performance has been successfully proved. Based on the result, we discovered that a 6 axes robot could execute 3D shape cutting of car hood due to its high movement flexibility. In the future it is projected to fulfill more kinds of CFRP materials cutting test on many car brands.
Rolled and extruded aluminum (Al) products have been widely used in heat exchanging systems using the boiling heat transfer (BHT) mechanism. The BHT coefficient can be increased on a rough surface due to the activation of the nucleation sites. In this study, the BHT characteristic of an Al plate with directional surface roughness (bare Al plate), which was generated in rolling or extrusion process, was measured and compared with the polished Al plates with non-directional surface roughness. The BHT coefficient of polished Al plate was increased with increasing surface roughness, saturated at ~300 nm (Sa). Although the surface roughness of the bare Al plate was 380-430 nm (Sa), the BHT coefficient of bare Al plates were lower than the polished Al plates with similar surface roughness. To examine the lower BHT coefficient of bare Al plate, the directional surface roughness was characterized by vertical and horizontal surface roughness values to the production direction, and we experimentally concluded the lower surface roughness value (horizontal surface roughness) was the dominant factor for the BHT characteristic of a rolled or extruded Al plate with directional surface roughness.
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Three-dimensional fin-tube expansion process to achieve high heat transfer efficiency in heat exchangers Seong-Yeop Kang, Sae-Rom So, Yong Son, Seonghun Park, Man-Yeong Ha, Sang-Hu Park Journal of Mechanical Science and Technology.2019; 33(9): 4401. CrossRef
Basic Experimental Study on Fin-Tube Expansion Process Using an Additive Manufactured Spiral-Grooved-Expanding Ball Seong Yeop Kang, Changwan Han, Yong Son, Seong Hun Park, Sang Hu Park Journal of the Korean Society for Precision Engineering.2019; 36(7): 667. CrossRef
Basic Experimental Study on Fin-Tube Expansion Process Using an Additive Manufactured Spiral-Grooved-Expanding Ball Seong Yeop Kang, Changwan Han, Yong Son, Seong Hun Park, Sang Hu Park Journal of the Korean Society for Precision Engineering.2019; 36(7): 667. CrossRef
A study about superhydrophobic surface started from the analysis of lotus leaf, and superhydrophobic surface fabrication methods have been researched. These methods cannot be used on various metals because the fabrication methods have complex and material-selective processes. In this work, we report a simple fabrication method using abrasive blasting and a self-assembled monolayer coating to produce a superhydrophobic surface. Abrasive blasting was used to create microstructures on metal surfaces. Random peak and valley microstructures were created after abrasive blasting, and a surface profile was measured to analyze the relationship between blasting pressure and a roughness parameter. A hydrophobic material coating was performed by a self-assembled monolayer method. Six kinds of metal surfaces displayed superhydrophobic properties. This utilitarian method could be applied to diverse applications.
Chemical mechanical polishing achieves surface planarity through combined mechanical and chemical means. The role of the chemical reaction is very important in a metal CMP like aluminum. The slurry used in aluminum CMP typically consists of oxidizers, a chelating agent, corrosion inhibitors, and abrasives. This study investigates the effect of oxalic acid as a chelating agent for aluminum CMP with H2O2. To study the chemical effect of the chelating agent, the two methods of a polishing experiment and an electrochemical analysis were used. Lastly, it was confirmed that the optimum concentration of oxalic acid significantly improved the removal rate and surface roughness of aluminum.
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Hybrid CMP Slurry Supply System Using Ionization and Atomization Hoseong Jo, Da Sol Lee, Seon Ho Jeong, Hyun Seop Lee, Hae Do Jeong Applied Sciences.2021; 11(5): 2217. CrossRef
Improvement of Interface Diffusion in Cu thin films using SiN/CoWB Passivation Layer Jung Woong Kim, Sean Jhin Yoon, Hyun Chan Kim, Youngmin Yun, Jaehwan Kim Journal of the Korean Society for Precision Engineering.2018; 35(12): 1163. CrossRef
Improvement of Interface Diffusion in Cu thin films using SiN/CoWB Passivation Layer Jung Woong Kim, Sean Jhin Yoon, Hyun Chan Kim, Youngmin Yun, Jaehwan Kim Journal of the Korean Society for Precision Engineering.2018; 35(12): 1163. CrossRef
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