• 한국정밀공학회지
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• 제30권11호
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• pp.1129-1137
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• 2013

We report a centerless grinding machine which can perform multi-function with 600 mm wide grinding wheels. By increasing manufacturing area, long workpiece such as camshaft and steering shaft, is allowed to grind more quickly, compared with cylindrical grinding system. In this paper, the design of centerless grinding machine puts emphasis on symmetry to exploit the thermal stability. Results of finite element analysis shows that the difference of the structural deflection in the front and rear guideways is less than $1.5{\mu}m$ due to symmetric design. The difference is less than $3.0{\mu}m$, even though the thermal deformation is considered. According to the performance evaluation, the radial error motion of the G/W spindle, which is measured by applying Donaldson Ball Reversal, is about 1.1${\mu}m$. The yaw error of the G/W slide is improved from 2.1 arcsec to 0.5 arcsec by readjusting the slide preload and ball screw.

• 문화기술의 융합
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• 제7권4호
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• pp.801-806
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• 2021

레일 파상마모는 레일표면 요철 관리기준의 부재로 인해 지속적으로 증가하는 추세에 있다. 레일파상마모는 승차감 저하와 궤도 유지관리 물량증대 등과 같은 다양한 문제점을 야기 시키고 있다. 본 논문에서는 레일 파상마모 발생구간을 대상으로 레일 연마 전, 후에 대한 레일요철 측정 및 궤도계측(동적 윤중, 변위, 가속도)을 수행하여 레일 파상마모가 궤도부담력에 미치는 영향을 분석하였다. 또한 레일 파상마모 저감을 위해 실시한 레일연마는 레일 파상마모로 인해 발생되는 추가적인 궤도부담력 저감에 매우 효과적이었음을 실험적으로 입증하였다.

• Design & Manufacturing
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• 제1권1호
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• pp.7-11
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• 2007

The fabrication of precision optical components by deterministic CNC grinding is an area of great current interest. Replacement of the traditional, craftsman driven, optical fabrication process is essential to reduce costs and increase process flexibility and reliability. Moreover, CNC grinding is well suited to the fabrication of complex shapes such as aspheres, making it possible to design optical systems with fewer components and reduced weight. Current technology is capable of producing surfaces with less than 2 microns peak to valley error, 50 nm rms surface roughness, and less than 1 micron subsurface damage. Bound abrasive tools, in which the abrasive particles are fixed in a second (matrix) material, play an important part in achieving this performance. In this paper, the factors affecting the ultra-fine surface roughness and profile accuracy of machined surfaces of aspheric parts has been analyzed experimentally and theoretically and on ultra-precision aspheric grinding system and precise adjusting mechanism have been designed and manufactured. In the paper we report the results of experiments and modeling performed to examine the effects of machinability, occurring during grinding of optical surfaces, on the tool surface profile. Profiles of machined surface were measured by using SEM. In order to optimize grinding conditions of aspheric lens processing, we performed experiments by design of experiments.

• Journal of Astronomy and Space Sciences
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• 제21권2호
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• pp.141-152
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• 2004

우주망원경용 비구면 반사경 가공 공정은 고정입자 연삭, 자유입자 래핑, 연마의 순서를 따른다. 숙련공에 의한 경험적 공정조절에 의해 목표 비구면을 가공하는 전통적 연삭 공정에서는 수 ${mu}m$ 높이의 표면 밑 손상을 남기며 뒤이은 자유입자 래핑 및 연마 공정에서 이를 제거하며 가공한다. 본 연구는 컴퓨터 수치 제어 연삭 공정진화 모델을 개발하여, 연삭가공을 통해 반사경 표면조도 최소 40nm이하, 가공 예측정확도 20nm급을 이루었다. 구체적인 방법론으로 초정밀가공기의 연삭모듈을 이용하여 연삭 휠 입자의 크기, 이송속도, 공작물 회전선속도 등 연삭 변수를 변화시키며 직경 20, 100mm Zerodur 소재를 초기 연삭하였다. 초기 연삭 변수와 측정된 표면조도와의 관계를 경험적 해석과 다 변수 회귀분석 해석 방법을 통하여 공정조절용 수치 연삭 모델을 구성하였다. 정량적 공정제어는 입력된 연삭변수들로부터 가공 후 표면조도를 예측하고, 측정된 표면조도를 이용하여 수치연삭 모델을 개량한 후 다음 가공에서 측정될 표면조도를 예측하는 순으로 만복 진행되었다. 본 연구에서는 CNC 연삭공정조절로부터 최소 평균 표면조도 36nm, 예측정확도 ${pm}20nm$를 얻었다. 이 연구결과는 정량적 연삭공정제어 모델을 사용하여 자유입자 래핑 공정을 수행할 필요 없이 연삭에서 직접 연마 공정으로 진행할 수 있는 획기적인 공정 효율 향상을 의미한다.

• 한국기계가공학회지
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• 제18권1호
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• pp.9-15
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• 2019

This study focused on the application of ELID mirror-surface grinding technology to the manufacture of off-axis asymmetric large-area reflecting mirrors made of BK7 glass. The size of the parts, such as asymmetric large-area mirrors or lens, made form-accuracy or roughness especially hard to measure after machining because of the measuring range limit of measurement devices. In this study, the ELID grinding system has been set up for mirror-surface machining experiments manufacturing off-axis asymmetric lenses. A measuring method using a reference workpiece has been suggested to measure the form-accuracy and roughness. According to the experimental results, even when using only a reference workpiece, it is confirmed that the surface roughness was 8 nmRa and form-accuracy was 80 nmRMS, with a best fit asymmetric radius when using a grinding wheel of #8,000. It is found that the accuracy of large-area parts could be estimated by the proposed process.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 1995년도 춘계학술대회 논문집
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• pp.1-8
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• 1995

This paper proposed a simple method for measuring surface roughness of ground surface. utilizing non-contact in-process measuring system using the diode laser. The measurement system is consisted of a laser unit with a diode laser and a cylindrical lens a detecting unit with polygon mirror and CCD array sensor. and a signal processing unit with a computer and device. During operation, this measuring system can provide information on surface roughness in the measuring distance with a single sampling and simultanilusly monitor the state of the grind wheel. The experimental results, showed that the increase of the feed rate and the dressing speed an caused increase in the surface roughness and when the surface roughness is 4Rmax-10Rmax, the cutting speed is 1653m/min-1665m/min. the feed rate is 0.2m/min-0.9m/min, the dressing speed is 0.2mm/rev-0.4mm/rev, the stylus method and the in-process method can be obtained the same results. thus under limited working conditions. using the proposed system. the surface roughness of the ground surface during cylindrical grinding can be obtained through the in-process measurement method using the diode laser.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2004년도 춘계학술대회 논문집
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• pp.298-303
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• 2004

parameters in surface grinding. Taguchi method which is one of the design of experiments has been introduced in achieving the aims. The process parameters were the grain size, the wheel speed, the depth of cut and the table speed. The effect of the process parameters on the geometric error was examined and an optimal set of the parameters was selected to minimize the geometric error within the controllable range of the used grinding machine. The reliability of the results was evaluated by the ANOVA.

• 한국재료학회지
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• 제9권2호
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• pp.111-116
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• 1999

The microstructure of vitreous bonded abrasives, which are used as the essential materials in the precise grinding, was investigated theoretically using two particle model. In this paper, a general equation applicable for a case in which there is a gap between abrasive grits is suggested. As a result, it was known that both the volume ratio of grit to glassy bond(V\ulcorner/V\ulcorner) and porosity(V\ulcorner) are the function of $\alpha$(the ratio of distance between grit to diameter of grit) and $\theta$(the angle from the center of pore to that of grit). Because the value $\alpha$ and $\theta$ can be get easily by using these suggested equations, the microstructure could be explained quantitatively. Also the raised error with the increasing amount of bond was modified by the simple assumption. As a result, in that case, both V\ulcorner/V\ulcorner and V\ulcorner were known to be the function of $\alpha$ and $\theta$(the ratio diameter of pore to that of grit).

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1992년도 춘계학술대회 논문집
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• pp.18-22
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• 1992

This paper presents the process of manufacturing technology of ceramics ferrule for optical fiber connector. Precision zirconia ceramic ferrules is widely used for high performance and low cost single mode optical fiber connectors. To polish the hole of the zirconia ceramic ferrule, the wire lapping instrument is developed and the machining experiment is conducted. Through the centerless grinding using diamond wheel the surface roughness of zirconia ceramics ferrule is below the 1 .mu. m Rmax.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2004년도 춘계학술대회 논문요약집
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• pp.32-32
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• 2004

산업이 발전함에 따라 기계부품의 소형화, 고속화가 요구되는 세계적인 추세에서 정밀 가공기술은 기계 및 전자 부품 산업에서 중요한 위치를 차지하게 되었다. 특히, 원통형상을 가지는 부품의 가공에서 무심 연삭(Centerless Grinding) 공정은 높은 생산성과 정확한 치수 형성의 능력이 있어서 중요한 생산공정으로 발전되어 왔다. 예컨대 각종 Pin, Compressor의 Crankshaft, 소형 축, 연료분사기 등은 무심 연삭 공정을 통하여 높은 정밀도를 얻고 있다. 본 발표에서는 최근 생산 현장에서 요구되고 있는 고효율 연삭 공정을 위한 Shaft류의 외경과 단면의 복합공정 연삭 방법을 기술하였다.(중략)