• Title/Summary/Keyword: Surface accuracy

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Cutting Condition Selection for Geometrical Accuracy Improvement in End Milling (엔드밀 가공에서 형상 정밀도 향상을 위한 절삭 조건 선정)

  • 류시형;최덕기;주종남
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 2003.06a
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    • pp.1784-1788
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    • 2003
  • For the improvement of geometrical accuracy in end milling, cutting method and cutting condition selection are investigated in this paper. As machining processes are composed of several steps such as roughing, semi-finishing. and finishing, cutting forces and tool deflection are calculated considering surface shape generated by the previous cutting. The effects of tool teeth numbers, tool geometry, and cutting conditions on the form error are analyzed. Using the from error prediction method from tool deflection, cutting condition for geometrical accuracy improvement is discussed. The characteristics and the difference of generated surface shape in up and down milling are dealt with and over-cut free condition in up milling is presented. The form error reduction method by alternating up and down milling is also suggested. The effectiveness of the presented method is examined from a set of cutting tests under various cutting conditions. This research contributes to cutting process optimization for the geometrical accuracy improvement in die and mold manufacture.

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IMAGE FUSION ACCURACY FOR THE INTEGRATION OF DIGITAL DENTAL MODEL AND 3D CT IMAGES BY THE POINT-BASED SURFACE BEST FIT ALGORITHM (Point-based surface best fit 알고리즘을 이용한 디지털 치아 모형과 3차원 CT 영상의 중첩 정확도)

  • Kim, Bong-Chul;Lee, Chae-Eun;Park, Won-Se;Kang, Jeong-Wan;Yi, Choong-Kook;Lee, Sang-Hwy
    • Journal of the Korean Association of Oral and Maxillofacial Surgeons
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    • v.34 no.5
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    • pp.555-561
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    • 2008
  • Purpose: The goal of this study was to develop a technique for creating a computerized composite maxillofacial-dental model, based on point-based surface best fit algorithm and to test its accuracy. The computerized composite maxillofacial-dental model was made by the three dimensional combination of a 3-dimensional (3D) computed tomography (CT) bone model with digital dental model. Materials and Methods: This integration procedure mainly consists of following steps : 1) a reconstruction of a virtual skull and digital dental model from CT and laser scanned dental model ; 2) an incorporation of dental model into virtual maxillofacial-dental model by point-based surface best fit algorithm; 3) an assessment of the accuracy of incorporation. To test this system, CTs and dental models from 3 volunteers with cranio-maxillofacial deformities were obtained. And the registration accuracy was determined by the root mean squared distance between the corresponding reference points in a set of 2 images. Results and Conclusions: Fusion error for the maxillofacial 3D CT model with the digital dental model ranged between 0.1 and 0.3 mm with mean of 0.2 mm. The range of errors were similar to those reported elsewhere with the fiducial markers. So this study confirmed the feasibility and accuracy of combining digital dental model and 3D CT maxillofacial model. And this technique seemed to be easier for us that its clinical applicability can good in the field of digital cranio-maxillofacial surgery.

Effect of Electrolyte Filtration Accuracy on Electrochemical Machining Quality for Titanium Alloy

  • Zhiliang Xu;Zhengyang Xu;Hongyu Xu;Zhenyu Shen;Tianyu Geng
    • Journal of Electrochemical Science and Technology
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    • v.15 no.2
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    • pp.299-313
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    • 2024
  • Electrochemical machining (ECM) is an effective manufacturing method for difficult-to-machine materials and is widely used in the precision manufacturing of aerospace components. In recent years, the requirements for the machining accuracy and surface integrity of ECM have become increasingly stringent. To further improve the machining quality, this work investigated the intricate laws between electrolyte filtration accuracy and machining quality. Electrolytes with different filtration accuracies were compared, and a numerical simulation was used to evaluate the change in temperature and bubble rate of the flow field in the machining area. Experiments were conducted on ECM of Ti-6Al-4V (TC4) alloy workpieces using electrolytes with different filtration accuracy. The workpiece machining accuracy and surface quality were analyzed, and the repetition accuracy of the workpiece was evaluated. The intricate laws between electrolyte filtration accuracy and machining quality were explored. It was found that when the electrolyte filtration accuracy is improved, so too is the machining quality of the ECM. However, once the filtration accuracy has reached a certain value, the machining quality has extremely limited improvement. By evaluating the repetition accuracy of processed workpieces in electrolytes with different filtration accuracies, it was found that when the filtration accuracy reaches a certain value, there is no positive correlation between the repetition accuracy and filtration accuracy. The result shows that, for the workpiece material and conditions considered in this paper, an electrolyte with 0.5㎛ filtration accuracy is suitable for the wide application of precision ECM.

Machining of Anode and Cavity applying Ultraprecision Machining Characteristics of OXFC (무산소동의 초정밀 절삭 특성을 이용한 아노드 및 캐비티의 가공)

  • 원종호;김주환;박순섭;김건희;김상석
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 2002.05a
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    • pp.922-925
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    • 2002
  • Klystron which is micro wave amplifier tube are mainly used in fields of science such as accelerator, nuclear fusion, broadcasting, communication fields, and defense industry fields, tract. The quality of Klystron anode and cavity are determined by form accuracy and roughness of the worked surface. Therefore anode and cavity are restricted the from accuracy strictly and the surface roughness be under Rmax 0.03S. As a work material of anode and cavity, the oxygen-free copper, that is used for optical pares of aerospace and laser mirror is selected. An outside diameter of material is $\Phi$100 mm and an inside diameter is $\Phi$30~33 mm. In this study, to find the optimum ultra precision cuffing condition of oxygen-free copper with diamond turning machine, the surface roughness is examined for various diamond toot nose radius, main spindle speed, fred rate and depth of cut. As a result of experiment, we could machined the anode and cavity with a surface roughness within Ra 3.2 nm, a form accuracy within 0.01 $\mu\textrm{m}$.

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Effect of subsurface flow and soil depth on shallow landslide prediction

  • Kim, Minseok;Jung, Kwansue;Son, Minwoo;Jeong, Anchul
    • Proceedings of the Korea Water Resources Association Conference
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    • 2015.05a
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    • pp.281-281
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    • 2015
  • Shallow landslide often occurs in areas of this topography where subsurface soil water flow paths give rise to excess pore-water pressures downslope. Recent hillslope hydrology studies have shown that subsurface topography has a strong impact in controlling the connectivity of saturated areas at the soil-bedrock interface. In this study, the physically based SHALSTAB model was used to evaluate the effects of three soil thicknesses (i.e. average soil layer, soil thickness to weathered soil and soil thickness to bedrock soil layer) and subsurface flow reflecting three soil thicknesses on shallow landslide prediction accuracy. Three digital elevation models (DEMs; i.e. ground surface, weathered surface and bedrock surface) and three soil thicknesses (average soil thickness, soil thickness to weathered rock and soil thickness to bedrock) at a small hillslope site in Jinbu, Kangwon Prefecture, eastern part of the Korean Peninsula, were considered. Each prediction result simulated with the SHALSTAB model was evaluated by receiver operating characteristic (ROC) analysis for modelling accuracy. The results of the ROC analysis for shallow landslide prediction using the ground surface DEM (GSTO), the weathered surface DEM and the bedrock surface DEM (BSTO) indicated that the prediction accuracy was higher using flow accumulation by the BSTO and weathered soil thickness compared to results. These results imply that 1) the effect of subsurface flow by BSTO on shallow landslide prediction especially could be larger than the effects of topography by GSTO, and 2) the effect of weathered soil thickness could be larger than the effects of average soil thickness and bedrock soil thickness on shallow landslide prediction. Therefore, we suggest that using BSTO dem and weathered soil layer can improve the accuracy of shallow landslide prediction, which should contribute to more accurately predicting shallow landslides.

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Development of Free-surface Decomposition Method and Its ApplicationDevelopment of Free-surface Decomposition Method and Its Application

  • Park, Sunho
    • Journal of Advanced Research in Ocean Engineering
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    • v.3 no.2
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    • pp.75-82
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    • 2017
  • With the development of computational fluid dynamics (CFD), studies on shipbuilding and maritime issues including free-surface wave flow have been conducted. Although the volume of fluid (VOF) and level-set methods are widely used to study the free-surface wave flow, disadvantages exist. In particular, it takes a long time to obtain solutions. In this study, a free-surface capturing code is developed for ship and offshore structures. The developed code focuses on accuracy and computation time. Open source CFD libraries, termed OpenFOAM, are used to develop the code. The results obtained using the developed code are compared with those obtained using interFoam. The results show that the developed code could be used to capture the free-surface wave flow without numerical diffusion; moreover, the accuracy of the developed code is largely the same as that of interFoam.

Prediction and analysis of the machined surface accuracy in end milling (엔드 밀링의 가공 표면 정밀도 예측과 해석)

  • 고정훈;윤원수;조동우
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 2000.11a
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    • pp.1018-1022
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    • 2000
  • Enhancement of the accuracy of products and productivity are essential to survive in a global industrial competition. This trend requires tighter dimensional tolerance specifications. To actively cope with the rapid change of the workpiece material and cutter geometry, a general method that can predict and analyze the machined surface is needed. Surface generation model for the prediction of the topography of machined surfaces is developed based on cutting force model considering cutter deflection and runout. This paper presents the method that constructs the three-dimensional machined surface error following the movement of a cutter, irrespective of the variations of cutting conditions. In addition, the effects of the cutting forces and the kink shape on the machined surface are extensively investigated.

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A research on Postprocess Finishing Method of The Rapid Prototyping Parts (쾌적조형 부품의 후처리 방안에 관한 연구)

  • 양화준;김성준;장태식;이일엽;이석희
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 1997.10a
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    • pp.83-86
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    • 1997
  • Even as many methods and technologies have been introduced on data generation, parts orientation and layer slicing to acquire the rapid prototyping(RP) parts that have useful surface to satisfy customers' needs such as stylingldesign verification directionlindirect tooling directly from the RP machine, these trials continue to suffer from the surface roughness due to the build characteristics of RP technology. A new postprocess finishing method is suggested in this paper to overcome the surface roughness problem on the surface of the RP parts. To prevent deterioration of dimensional accuracy from the conventional grinding-only, and coating-grinding methods, 4-step surface finishing process is applied. To satisfy the various requirements from the RP oriented industrial f elds, effective procedure, coating material, grmd~ng tools and methods are employed.

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A Study on the Improvement of Accuracy and Precision in the Vision-Based Surface-Strain Measurement (비전을 이용한 곡면변형률 측정의 정확도 및 정밀도 향상에 관한 연구)

  • 김두수;김형종
    • Transactions of Materials Processing
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    • v.8 no.3
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    • pp.294-305
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    • 1999
  • A vision-based surface-strain measurement system has been still improved since the authors devel-oped the first version of it. New algorithms for the subpixel measurement and surface smoothing are introduced to improve the accuracy and precision in the present study. The effects of these algorithms are investigated by error analysis. And the equations required to calculate 3D surface-strain of a shell element are derived from the shape function of a linear solid finite-element. The influences of external factors on the measurement error are also examined, and several trials are made to obtain possible optimal condition which may minimize the error.

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Ultra-precision Grinding Machining of Glass Rod Lens Core With Aspheric (비구면 Glass Rod 렌즈 금형의 초정밀 연삭가공)

  • Kim, Woo-Soon;Kim, Dong-Hyun
    • Transactions of the Korean Society of Machine Tool Engineers
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    • v.18 no.1
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    • pp.76-82
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    • 2009
  • To obtain the surface roughness with nano order, we need a ultra-precision machine, cutting condition, and materials. In this paper, the cutting condition for getting nano order smooth surface of core have been examined experimentally by the ultra-precision machine and diamond wheels. The effects of the cutting velocity, the feed rate and depth of cut on the surface roughness were studied. And also, the surface roughness was measured by the Form Talysurf series PGI 840. The champion data of developed core was surface roughness Rmax 24.6nm, figure accuracy Rmax 68.9nm.