• Journal of the Korean Society for Heat Treatment
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• v.18 no.6
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• pp.355-361
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• 2005

In this study, the effects of the maximum undeformed chip thickness on grinding characteristics of hardened steel in down-grinding have been investigated. The meaured grinding forces become larger as the workpiece velocity increases. The specific energy, e decreases as the maximum undeformed chip thickness increase. When the maximum undeformed chip thickness is the same, the specific energy, e decreases as the grain size increases.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.5 no.1
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• pp.33-38
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• 2006

Silicon has been widely used in electronic parts as a semiconductor equipment. It, however, requires much effort to grind without microcrack and chipping because of its high hardness and brittleness. So far, many studies for the grinding of engineering ceramics have been done, but not for the grinding of silicon. In this paper, a theoretical analysis on the grinding forces is introduced. Grinding experiments were performed at various grinding conditions including grinding directions (Up grinding and Down grinding), table speeds and depth of cuts. The grinding forces were measured to compare at various grinding conditions. The experimental values agree well with theoretical ones.

• Journal of the Korean Society for Precision Engineering
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• v.19 no.9
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• pp.59-65
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• 2002

Grinding temperature between a grinding wheel and a workpiece surface, rising rapidly during a machining operation, has bad effects on a surface integrity such as the burning, the residual stress and the crack. In this study, the temperature distribution was obtained briefly by the finite element method and the grinding temperature of a workpiece varying with the grinding condition was measured experimentally. For obtaining the grinding temperature, a thermocouple method was applied. Three thermocouples were inserted in a surface of each workpiece. Changed grinding conditions were the depth of cuts, the feedrate, the dry and wet grinding, the up and down grinding and the number of pieces.

• Journal of the korean Society of Automotive Engineers
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• v.13 no.6
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• pp.109-118
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• 1991

In this study, it is intended to investigate the effect of the grinding conditions such as table feed, down feed, cross feed of residual stress distribution. And this distribution is investigated upon the grinding direction and the its orthogonal direction at ground layers. The material is used carbon steel (SM20C) which usually used to motor axis. And in order to be considered as Bernoulli-Euler beam, the dimension of the specimen is appropriately designed. According as corroiding the ground surface, the residual stress layers are removed and strain which occured on account of unbalance of internal stress is detected by rosette-gate. Through A/D converter and computer, these values are saved and evaluated residual stress by stress-strain relation formula. Finally, these results are diagrammatized with Auto Cad. The results obtained are as follows. As the depth from the ground surface increases in grinding direction and its orthogonal direction, tensile residual stress exists in the surface, and subsequently it becomes compressive residual stress as it goes downward. As the table feed, the cross feed and the down feed increase, maximum residual stress is transformed form the tensile to the compressive.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.05a
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• pp.46-51
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• 2002

A grinding technology is very essential to finish the surface of IT and BT industrial application parts such as wafer, optical connection part and lenses etc. However the finding machine has bead depended on imports. Especially, it is completely imported for machining high precision part relevant to domestic electric and communicational industries. The amount to import grinding machine is about $110milions. It takes about 35% of total import amount of all the machine tools. A domestic finder manufacturer is a very small-scaled bussinessman and research facilities is poor. Recently, it is increasing to demand high speed and precision grinding technology because it brings cost down and value added up. Its further study will be something related to inteligent grinding system fur value added and high precision part. It will make domestic grinding technology to its advanced country level.

• Journal of the Korean Society for Nondestructive Testing
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• v.11 no.2
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• pp.32-41
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• 1991

This paper is to analyze the surface roughness in wet and dry surface grinding in which working conditions are table feed, cross feed and down feed. FFT analyzer is used to identify the surface roughness and the data of surface roughness are stored and displayed using an interfaced computer. In results, components affecting surface roughness exist within 200Hz with respect the conditions and methods of grinding operation. Also, with increase of table feed, cross feed and down feed, the value of surface roughness increases. Of them, cross feed has first influence on surface roughness. In dry, preciser surface can be obtained than one in wet.

• Journal of the Korean Society of Safety
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• v.5 no.1
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• pp.31-39
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• 1990

In this paper, the influence of the table speed, metal removal rate and grinding fluid on long wheel workpiece contact zone at high effect grinding was investigated by theoretical analyses and measuring the temperature, and discussed by the temperature distribution in grinding surface layer. Main results obtained are as follows, 1) Rega.dless of the table speed, the temperature gap of the workpiece(heat influx) is about 6-8 times as high in dry condition as in wet condition. 2) Good grinding condition can be obtained owing to the effect of grinding fluid without any burning defect under the condition of the metal removal rate(1.0mm$^3$/mm.s) in case of wet grinding. 3) When the depth from the surface layer is about 1.25-1.5mm under the condition of the slow table speed, surface temperature goes up higher as the table speed slows down, because long contact time is laked at the surface layer. 4) In case of the same metal removal rate, the lower the table speed becomes, the higher the surface temperature is, because grinding depth has a far more influence on wheel workpiece contact zone than the table speed.

• Journal of Astronomy and Space Sciences
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• v.21 no.2
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• pp.141-152
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• 2004

Optics fabrication process for precision space optical parts includes bound abrasive grinding, loose abrasive lapping and polishing. The traditional bound abrasive grinding with bronze bond cupped diamond wheel leaves the machine marks of about $20{mu}m$ rms in height and the subsurface damage of about 1 ${mu}m$ rms in height to be removed by subsequent loose abrasive lapping. We explored an efficient quantitative control of precision CNC grinding. The machining parameters such as grain size, work-piece rotation speed and feed rate were altered while grinding the work-piece surfaces of 20-100 mm in diameter. The input grinding variables and the resulting surface quality data were used to build grinding prediction models using empirical and multi-variable regression analysis. The effectiveness of such grinding prediction models was then examined by running a series of precision CNC grinding operation with a set of controlled input variables and predicted output surface quality indicators. The experiment achieved the predictability down to ${pm}20$ nm in height and the surface roughness down to 36 nm in height. This study contributed to improvement of the process efficiency reaching directly the polishing and figuring process without the need for the loose abrasive lapping stage.

• Journal of Biosystems Engineering
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• v.22 no.4
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• pp.439-450
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• 1997

Most of Korean feed mill has a pregrind system which was suitable for the processing of less number of ingredients and finished products, and good for the mash type feed product. But industries has been changed in production volume and cost, and also from mash to further processed products such as pelleted and extruded. Therefore, Korea feed industries now should change the process, especially the grinding system from the current pregrind to other grind system, but this change will cost a lot of investment and also loosing current grinding system, and should have production shut down during the construction period. To solve these problems, combined grinding system based on a new model mill has been developed. The combined grind system is combination of pregrind and postgrind system, which has the advantages of those two grind systems, and also which can allow to utilize existing pregrind system continuously without any production interruption due to new postgrind system construction. This newly developed model has been applied to the feed mill expansion project of `B`feed company in 1994, and it was very successful application and showed excellent results as we intended. The new model mill, combined grind system applied can save fixed asset investment because old pregrind system can be used as is, and also can reduce production cost and improve product quality. And the possibility of critical production shut down can be much lowered. Within this new grinding model development, multi-screen combination system has been developed for the better grinding texture quality and safer operation. This new model mill with combined grind system will be applied by most feed manufacturing plant and may enhance their production competitiveness, and the further study and development should be continued.

• Journal of the Korean Society for Precision Engineering
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• v.21 no.9
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• pp.196-203
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• 2004

SL(Stereolithography) part is made by piling up thin layers which causes the stair stepping effect at the surface of SL parts. The effect brings about excessive surface roughness and cuts down the merits of using SL part. Hence, additional post-machining finishing such as traditional grinding is required. But the traditional post-machining is detrimental to part geometry and time consuming. In this study, therefore, a paraffin coating and grinding post-machining is newly proposed to improve the surface quality of SL fart. The paraffin which has suitable properties for the proposed post-machining is coated all over the part surface. By grinding the only over-coated paraffin based on boundary of the SL part surface, the surface roughness can be improved without any damage on the part. Also, it is verified that SL part finished by the proposed post-machining process can be applied for rapid tooling as pattern through manufacturing silicon rubber molding and casting test.