Bong-Cheol Shin

Magnetorheological (MR) Polishing of Alumina-Reinforced Zirconia Ceramics Using Diamond Abrasives for Dental Application

In this study, ultraprecise polishing of alumina reinforced zirconia ceramics using magneto rheological (MR) fluids and diamond abrasives was investigated. First, alumina-reinforced zirconia composites, containing 0 to 30 vol% alumina, were fabricated by cold isostatic pressing at 150 MPa. The green compacts were then sintered at 1,550°C for 2 h in air. Mechanical properties and microstructures of the composites were observed. Second, a series of MR polishing experiments were performed for composites containing 20 vol% of alumina under various polishing conditions. MR polished surfaces were observed using a scanning electron microscope (SEM) and surface profiler to investigate the variation of the surface integrity. A very fine surface roughness of Ra = 1.960 nm was obtained after 60 minutes of MR polishing using diamond abrasives.

A Web-based machining process monitoring system for E-manufacturing implementation

Recently, with the rapid growth of information technology, many studies have been performed to implement Web-based manufacturing system. Such technologies are expected to meet the need of many manufacturing industries who want to adopt E-manufacturing system for the construction of globalization, agility, and digitalization to cope with the rapid changing market requirements. In this research, a real-time Web-based machine tool and machining process monitoring system is developed as the first step for implementing E-manufacturing system. In this system, the current variations of the main spindle and feeding motors are measured using hall sensors. And the relationship between the cutting force and the spindle motor RMS (Root Mean Square) current at various spindle rotational speeds is obtained. Thermocouples are used to measure temperature variations of important heat sources of a machine tool. Also, a rule-based expert system is applied in order to decide the machining process and machine tool are in normal conditions. Finally, the effectiveness of the developed system is verified through a series of experiments.

Assessment of Design and Mechanical Characteristics of MEMS Probe Tip with Fine Pitch

The probe card are test modules which are to classify the good semiconductor chips and thin film before the packaging process. In the rapid growth a technology of semiconductor, the number of pads per unit area is increasing and pad arrays are becoming irregular. Therefore, the technology of probe card needs narrow width and lots of probe tip. In this paper, the probe tip based on the MEMS(Micro Electro Mechanical System)technology was developed a new MEMS probe tip for vertical probe card applications. For the structural designs of probe tip were performed to mechanical characteristics and structural analysis using FEM(Finite Element Method). Also, the contact force of MEMS probe tip compared with FEM results and experimental results. Finally, the MEMS probe card was developed a fine pitch smaller than 50㎛.

A study on flow coefficient evaluation by shape change of butterfly valve

Abstract Butterfly valves have been used to control the flow rate of various fluids in many industries because it have unique manageability compare to other valves. The flow rate passing through the butterfly valves can be controlled according to the coefficient of capacity calculated by disk angle change. In this study, flow analysis by 3D modeling was performed to derive the coefficient of capacity to evaluate and improve newly developed butterfly valves. Also, required measurement system was established to verify the performance of the valves, and to compare with the calculated results. Key Words : Grooved butterfly valve, capacity of coefficient, Disc Open Angle 본 연구는 중소기업청 산학협력실 지원사업에 의해 수행되었음. * Corresponding Author : Bong-Cheol ShinTel: +82-32-860-7306 email: kenny77b@empal.com접수일 12년 07월 19일 수정일 (1차 12년 10월 09일, 2차 12년 10월 31일) 게재확정일 12년 11월 08일 1. 서론 최근 들어 국내 발전 설비 및 제조 공장의 설비가 증가하고 기존 설비의 유지 보수 또한 증가 하고 있는 추세이다. 이러한 시설에 고온, 고압의 기체 및 유체의 제어를 위해 밸브가 필수적으로 요구되고 있고 용도에 따라 게이트 밸브, 볼 밸브, 글로브 밸브, 버터플라이 밸브 등이 많이 사용되고 있다.[1] 이중 버터플라이 밸브는 기존의 다른 밸브의 비해 크기가 작고 완전 개폐 동작이 빠르다는 장점과 정밀 유체 제어가 가능하다는 장점을 가지고 있다. 따라서 국내 건축 및 플랜트 산업에서는 정밀 유체 제어를 위해 생활 및 공업용수의 급·배수에서 많을 활용을 하고 있다.[2,3]또한 grooved butterfly valve는 고온, 고압의 환경조건에서도 활용되기 때문에 내구성과 신뢰성과 더불어 정밀 유체 제어가 가능한 고품질 밸브가 필수적으로 요구되고 있다. 외국 제품의 경우에는 설계 단계부터 생산단계의 전 공정이 전문적인 인력 및 측정 장비를 이용해 수행되고 있어 밸브의 성능 평가에서 중요한 용량 계수를 각도에 따라 정확히 명시하고 있다. 국내 밸브의 경우 외국의 인건비 상승으로 인해 국내 OEM 방식으로 생산하고 있으며 이러한 방식을 통해 국외로 수출하는 회사를 제외하고는 영세한 규모의 기업환경 조건에

A Study on the Analysis of Multi-beam Energy for High Resolution with Maskless Lithography System Using DMD

Exposure process is the most important technology to fabricate highly integrated circuit. Up to now, mask type lithography process has been generally used. However, it is not efficient for small quantity and/or frequently changing products. Therefore, maskless lithography technology is raised in exposure process. In this study, relations between multi-beam energy and overlay were analyzed. Exposure experiment of generating pattern was performed. It was from presented scan line by multi- beam simulation. As a result, optimal scan line distance was proposed by simulation, and micro pattern accuracy could be improved by exposure experiment using laser direct imaging system.

A Web-based on-machine mould matching and measurement system based on CAD/CAM/CAI integration

The purpose of this study is to develop a Web-based on-machine mould identification and measurement system. The Web-based mould identification system matches obtained vision information with CAD database. Developed Web-based system is to exchange messages between a server and a client by making of ActiveX control, and the result of mould identification is shown on Web-browser at remote site. For effective feature classification and extraction, the signature method is used to make meaningful information from obtained image data. For on-machine measurement of the matched mould, inspection database is constructed from CAD database using developed inspection planning methods. The results are simulated and analyzed using developed system to verify the effectiveness of the proposed methods.