• Journal of the Korean Society of Manufacturing Process Engineers
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• v.12 no.2
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• pp.121-126
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• 2013

Precision machine tools for high dignity cutting are needed for efforts to improve machining accuracy. However, there are many factors to improve machining accuracy. This study investigated how machining accuracy changes when variation and unbalance amount in rotational speed domain is decreased. Machining accuracy of initial machine tools depends on manufacturing and assembly of parts such as bearing. And then, vibration and noise vary with volume of unbalance amount when it is rotation, so it effects unbalance amount. Also vibration and noise increased by unbalance shorten spindle's life and it especially makes worse boring accuracy. Therefore, this study studied the change of roundness and cylindricity of workpiece when it decreases variation and unbalance in rotational speed domain.

• Journal of Mechanical Science and Technology
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• v.17 no.7
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• pp.1036-1043
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• 2003

A computer simulation method for investigating the form generation mechanism in the centerless through-feed grinding process is described. The length of the contact line and the magnitude of the grinding force between the grinding wheel and workpieces, vary with the change in the axial location of the current workpiece during grinding. Thus, a new coordinate system and a grinding force curve of previous and/or following workpieces are introduced to treat the axial motion. Experiments and computer simulations were carried out using four types of cylindrical workpiece shapes. To validate this model, simulation results are compared with the experimental results.

• Journal of the KSME
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• v.34 no.3
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• pp.158-167
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• 1994

제품 기능의 고도화에 부응하여 요구되는 부품의 정밀도가 높아지고, 이러한 부품에 대한 수요가 증가함에 따라 형상 공차에 대한 관심과 활용은 증대되고 있다. 그러나 특히 3차원적 특성을 갖고 있는 원통도와 같은 형상 공차는 그 정의 자체가 내포하고 있는 문제점 및 측정기술의 한 계로 인하여 생상공정과의 직접적인 연결 및 활용에 큰 어려움이 있다. 따라서 원통도의 특성, 가공 형상에 영향을 미치는 인자 및 가공 공정과 가공형상과의 관계를 분석 . 종합한 결과를 기초로 하여 현재의 문제점들에 대처할 수 있는데 기본이 되는 세 가지 가정을 도출하였다. 이 러한 가정들을 이용하여 제안되는 새로운 검사공정은 검사 소요시간, 불량품 검출과 최종제품의 성능 및 신뢰도 확보 측면에서 효과적일 것으로 기대된다. 본문 중에서도 밝힌 바와 같이, 일부 가정은 그 타당성의 근거가 되는 연구 결과가 불충분하여 가능성만을 타진하였다. 따라서 이러한 분야에 대한 연구는 지속적으로 계속되어야 하며, 평면도와 같은 다른 형상공차에 대하여 제시된 방법론의 수정 적용 가능성도 검토되어야 할 것이다.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.1555-1558
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• 2005

In this study, we measured cylindricity and Runout of the air bearing spindle, and tested PCB(printed circuit boards) drilling with 0.4mm micro drill at 90,000rpm and 110,000rpm in order to obtain drilling hole error. Results are as follows; The air bearing spindle's Runout was not so high within $10\mu{m}$ from 20,000rpm to 80,000rpm but it grew after 80,000rpm. Drilling hole size error was 9% at 80,000rpm and 12% at 110,000rpm because of spindle's Run out. Drilled hole shape falsified more 110,000rpm than 90,000rpm.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.05a
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• pp.9-14
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• 2002

Ferrule is widely used as fiber optic connecters. In fiber-optic communications, the shape accuracy such as coaxiality and cylindricity of ferrule affects insertion loss. When coaxial grinding of ferrule supported by two pin, pin alignment and chucking accuracy are very important. In this research, the kinematic behavior of the ferrule center is investigated in the case where cone-shaped center pins and round circle hales which make contact with each other near the edge of the holes, using homeogenous coordinate transformation and numerical analysis. The obtained results are as follows: The alignment errors between center pins alone do not affect the rotation accuracy of ferrule. The alignment errors between center holes cause a sinusoidal displacement of ferrule. And the maximum displacement of ferrule centers increase in proportion to the center pin angle in the case of a fixed alignment errors

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.10 no.4
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• pp.82-87
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• 2011

Lubrication has an important role to reduce frictional forces and temperature between cutting chips and the face of a tool. However, it has harmful effects to workers' health and working environment. The purpose of this thesis is to find cutting conditions through the quality analysis in boring for SM45C steel using MQL(Minimum Quantity Lubrication). Machining process is super drill, tip drill, end mill and boring in order. Experimental factors of boring and the quantity of mist air are properly selected. With the analysis of experimental data, this thesis shows that boring with MQL improves the surface roughness when spindle speed is 934rpm or feeding speed is 74mm/min.

• Journal of the Korean Society for Precision Engineering
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• v.17 no.3
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• pp.174-183
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• 2000

Non-Parallelism the axial direction occurs during grinding process of long slender shafts. The reason for the axial error is due to elastic deformation of the components, accumulation phenomenon of the grinding and wheel wear during the grinding process. The accumulation phenomenon, the size generation mechanism and the wheel wear process during traverse grinding result in complicated process at each step on the wheel surface. The grinding system stiffness obtained from the stiffness of the center on the tailstock and the workpiece varing according to the relative position of the wheel and the workpiece. Further more, the value of wheel wear increases as the grinding process advances. The above mentioned issues make the shape generation process during traverse grinding quite complicated. This research analyzes the shape generation process in the direction of the work spindle. First, the formulation of the grinding system stiffness was conducted and the simulation analysis method of the traverse grinding was established. Also, a measuring system for assessing the dimensinal accuracy of the workpiece has been developed.

• Journal of the Korean Society for Precision Engineering
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• v.20 no.7
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• pp.7-12
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• 2003

각광을 받고 있는 광통신 분야의 핵심부품인 페룰은 일본이 전 세계의 95%를 장악하고 있다. 국내에서도 일부 업체에서 양산을 하고 있으나, 핵심 연삭공정에 사용되는 연삭 가공장비는 전량 수입되고 있는 실정이다. 페룰은 0.1∼0.3$\mu\textrm{m}$의 동심도, ${\pm}$ 0.2$\mu\textrm{m}$의 외경치수, 0.1$\mu\textrm{m}$대의 진원도와 원통도, 10nm의 표면 거칠기를 구현해야 세계적 경쟁력을 갖출 수 있는 초미세, 초정밀 기계가공 부품이다.(중략)

• Journal of Mechanical Science and Technology
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• v.17 no.7
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• pp.1044-1053
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• 2003

There are two major differences between the centerless infeed grinding process and the centerless through-feed grinding process. One is an axial movement of workpieces, and the other is that several workpieces are ground simultaneously and continuously by through-feeding. Because of these differences, through-feed ground parts inherently possess not only the roundness error but also the tapering error. The aims of the research reported in this paper are to examine this inherent tapering characteristic and to find the effects of grinding variables (center height angle, regulating wheel tilt angle, and shape of grinding wheel surface). To accomplish the objectives, experiments were carried out using two types of cylindrical workpiece shapes. Also, computer simulations were performed using the 3-D through-feed grinding model.

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.987-991
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• 2003

Ferrule is widely used as fiber optic connecters. In fiber-optic communications, the shape accuracy such as coaxiality and cylindricity of ferrule affects insertion loss. When coaxial grinding of ferrule supported by two pin, pin alignment and chucking accuracy are very important. In this research, the kinematic behavior of the ferrule center is investigated in the case where cone-shaped center pins and round circle holes which make contact with each other near the edge of the holes, using homeogenous coordinate transformation and numerical analysis. The obtained results are as follows: The alignment errors between center holes cause a sinusoidal displacement of ferrule. And the maximum displacement of ferrule centers increase in proportion to the center pin angle. The relationship between center pins displacement in coaxial grinding and grinding accuracy was explained.