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Reliability Evaluation of an Oil Cooler for a High-Precision Machining Center
Seung-Woo Lee,Seung-Woo Han,Husang Lee 한국정밀공학회 2007 International Journal of Precision Engineering and Vol.8 No.3
Improving the reliability or long-term dependability of a system requires a different approach from the previous emphasis on short-term concerns. The purpose of this paper is to present a reliability evaluation method for an oil cooler intended lor high-precision machining centers The oil cooler system in question is a cooling device that minimizes the deformation caused pam the heat generated by driving devices. This system is used lor machine tools and semiconductor equipment. We predicted the reliability of the system based on the failure rate database and conducted the reliability test using a test-bed to evaluate the life of the oil cooler. The results provided an indication a/the reliability a/the system in terms of the failure rate and the MTBF of the oil cooler system and its components, as well as a distribution of the failure mode. These results will help increase the reliability of oil cooler systems. The evaluation method can also be used to determine the reliability of other machinery products.
이호철(Hocheol Lee),이남영(Namyoung Lee),송창규(Changkyu Song),박천홍(Chunhong Park),이후상(Husang Lee) 대한기계학회 2005 대한기계학회 춘추학술대회 Vol.2005 No.5
In this paper, we suggest a polishing head with a mechanical gimbals-like structure for the optics fabrication. In the small tool polishing processes, several types of polishing mechanism have been tried to get more deterministic and high efficient optical fabrication. The conventional polishing processes to use the contacting pad material of polyurethane or pitch need the higher polishing rate to shorten the overall polishing time for large optics. Therefore, new polishing head mechanism is designed to use the air backpressure and gimbals-like hinge structure to increase polishing velocity. In the following experiment, mechanical adaptability was confirmed both on the flat glass and the convex aluminum surface.
전자빔 가공기용 진공 5 축 스테이지의 제어 및 운동특성
이찬홍(Chan-Hong Lee),박천홍(Chun-Hong Park),이후상(Husang Lee) 한국정밀공학회 2004 한국정밀공학회 학술발표대회 논문집 Vol.2004 No.10월
The ultra precision machining in industrial field are increased day by day. The diamond turning has been used generally, but now is faced with limitation of use, because of higher requirement of production field. The electron beam lithography is alternative in machining area as semiconductor production. For EB lithography, 5 axis vacuum stage is required to duplicate small and large patterns on wafer. The stage is composed of 2 rotational axis and 3 translational axis with 5 DC servo motors. The positioning repeatability and resolution of Z axis feed unit are 3.21㎛ and 0.5㎛/step enough to apply to lithography.
Park, Chun-Hong,Lee, Chan-Hong,Lee, Husang Korean Society for Precision Engineering 2004 International Journal of Precision Engineering and Vol.5 No.3
Effectiveness of a corrective machining algorithm, which can construct the proper machining information to improve motion errors utilizing measured motion errors, is verified experimentally in this paper, Corrective machining process is practically applied to single and double side hydrostatic bearing tables. Lapping process is applied as a machining method. The machining information is obtained from the measured motion errors by applying the algorithm, without any information on the rail profile. In the case of the single-side table, after 3 times of corrective remachining, linear and angular motion errors are improved up to 0.13 $\mu\textrm{m}$ and 1.40 arcsec from initial error of 1.04 $\mu\textrm{m}$ and 22.71 arcsec, respectively. In the case of the double-side table, linear and angular motion error are improved up to 0.07 /$\mu\textrm{m}$ and 1.42 arcsec from the initial error of 0.32 $\mu\textrm{m}$ and 4.14 arcsec. The practical machining process is performed by an unskilled person after he received a preliminary training in machining. Experimental results show that the corrective machining algorithm is very effective and easy to use to improve the accuracy of hydrostatic tables.
Corrective Machining Algorithm for Improving the Motion Accuracy of Hydrostatic Bearing Tables
Park, Chun-Hong,Lee, Chan-Hong,Lee, Husang Korean Society for Precision Engineering 2004 International Journal of Precision Engineering and Vol.5 No.2
For improving the motion accuracy of hydrostatic tables, a corrective machining algorithm is proposed in this paper. The algorithm consists of three main processes. The reverse analysis is performed firstly to estimate the rail profile from the measured linear and angular motion error, in the algorithm. For the next step, the corrective machining information is obtained based upon the estimated rail pronto. Finally, the motion errors on the correctively machined rail are analyzed by using the motion error analysis method. These processes are iterated until the analyzed motion errors are satisfactory within the target accuracy. In order to verify the validity of the algorithm theoretically, the motion errors calculated by the estimated rail after the corrective machining process, are compared with those by the true rail which is previously assumed as the initially measured value. The motion errors calculated using the estimated rail show good agreement with the assumed values, and it is shown that the algorithm is effective in acquiring the corrective machining information to improve the accuracy of hydrostatic tables.