• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2000년도 춘계학술대회 논문집
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• pp.917-921
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• 2000

One of the major limitations of productivity and quality in machining is machining accuracy of the machine tools. The machining accuracy is affected by geometric, volumetric errors of the machine tools. This paper suggests the enhancement method of machining accuracy for precision machining of high quality metal reflection mirror or optics lens, etc. In this paper, we study 1) the compensation of linear pitch error with NC controller compensation function using laser interferometer measurement, 2) the method for enhancing the accuracy of NC milling machining by modeling and compensation of volumetric error, 3) the generation of the parabolic face profile. And the method is verified by the parabolic face machining experiment with a vertical three axes NC milling machine. After this study, we will inspect using On-machine measurement and study the repetitive machining by a compensated path

• 한국정밀공학회지
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• 제16권11호
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• pp.224-233
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• 1999

The quality of injection molded parts is affected by the variables such as materials, design variables of part and mold, molding machine, and processing conditions. It is difficult to consider all the variables at the same time to predict the quality. In this paper neural network was applied to analyze the relationship between processing conditions and volumetric shrinkage of part. Engineering plastic gear was used for the study, and the learning data was extracted by the simulation software like Moldflow. Results of neural network was good agreement with simulation results. Nonlinear regression model was formulated using the test data of 3,125 obtained from neural network, Optimal processing conditions were calculated to minimize the volumetric shrinkage of molded part by the application of RQP(Recursive Quadratic Programming) algorithm.

• International Journal of Precision Engineering and Manufacturing
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• 제1권1호
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• pp.111-117
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• 2000

One of the major limitations of productivity and quality in metal cutting is the machining accuracy of machine tools. The machining accuracy is affected by geometric errors, thermally-induced errors, and the deterioration of the machine tools. Geometric and thermal errors of machine tools should be measured and compensated to manufacture high quality products. In metal cutting, the machining accuracy is more affected by thermal errors than by geometric errors. This paper models the thermal errors for error analysis and develops an on-the-machine measurement system by which the volumetric errors are measured and compensated. The thermal error is modeled by means of angularity errors of a column and thermal drift error of the spindle unit which are measured by the touch probe unit with a star type styluses and a designed spherical ball artifact (SBA). Experiments show that the developed system provides a high measuring accuracy, with repeatability of $\pm$2$\mu\textrm{m}$ in X, Y and Z directions. It is believed that the developed measurement system can be also applied to the machine tools with CNC controller. In addition, machining accuracy and product quality can be also improved by using the developed measurement system when the spherical ball artifact is mounted on a modular fixture.

• International Journal of CAD/CAM
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• 제8권1호
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• pp.41-44
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• 2009

This paper describes an implementation of virtual teeth modeling for a haptic dental simulation. The system allows dental students to practice dental procedures with realistic tactual feelings. The system requires fast and stable haptic rendering and volume modeling techniques working on the virtual tooth. In our implementation, a volumetric implicit surface is used for intuitive shape modification without topological constraints and haptic rendering. The volumetric implicit surface is generated from input geometric model by using a closest point transformation algorithm. And for visual rendering, we apply an adaptive polygonization method to convert volumetric teeth model to geometric model. We improve our previous system using new octree design to save memory requirement while increase the performance and visual quality.

• 한국정밀공학회지
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• 제18권7호
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• pp.98-105
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• 2001

The machining accuracy is affected by geometric, volumetric errors of the machine tools. To improve the product quality, we need to enhance the machining accuracy of the machine tools. To this point of view, measurement and inspection of finished part as error analysis of machine tools ahas been studied for last several decades. This paper suggests the enhancement method of machining accuracy for precision machining of high quality metal reflection mirror or optics lens, etc. In this paper, we study 1) the compensation of linear pitch error with NC controller compensation function using laser interferometer measurement, 2) the method for enhancing the accuracy of NC milling machining by modeling and compensation of volumetric error, 3) the spherical surface manufacturing by modeling and compensation of volumetric error of the machine tool, 4) the system development of OMM without detaching work piece from a bed of machine tool after working, 5) the generation of the finished part profile by OMM. Furthermore, the output of OMM is compared with that of CMM, and verified the feasibility of the measurement system.

• 방송공학회논문지
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• 제27권2호
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• pp.207-215
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• 2022

최신 볼류메트릭 기술이 제공하는 높은 기하학적 정확도와 사실성은 실제 객체와 캡춰된 3D 모델 간 높은 일치도를 보장한다. 그럼에도 불구하고 이렇게 획득된 3D 모델은 프레임 간 완전히 독립적인 3D모델로 시퀀스를 구성하고 있다는 측면에서, 매 프레임 모델 표면 구조(Geometry)의 일관성이 보장 되지 않으며, 정점(Vertex)의 밀도가 매우 높고 정점 간 연결 노드(Edge)가 매우 복잡해지는 특징을 확인 할 수 있다. 이 기술을 통해 생성된 3D 모델은 영화나 비디오 게임 제작 파이프라인에서 제작된 모델과는 본질적으로 다르며, 실시간 렌더링, 애니메이션 및 시뮬레이션, 압축과 같은 응용 분야에서 직접 사용하기에 적합하지 않다. 이와는 대조적으로 우리의 방법은 프레임 간 3D 모델 표면 구조의 높은 일관성을 확보하는 리메싱(Remeshing)과 비강체 표면(Non-rigid Shape)의 대응(Correspondences) 및 매칭(Matching)을 통한 점진적 변형(Deformation) 과정 및 텍스쳐 전달(Texture Transfer) 과정을 연결함으로서 볼류메트릭 3D 모델 시퀀스 품질의 일관성을 유지하며, 후 처리 과정의 자동화를 제공한다.

• 방송공학회논문지
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• 제27권5호
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• pp.751-761
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• 2022

디지털 기술의 발전에 따라 메타버스가 콘텐츠 시장의 주요 트렌드로 자리하면서 고품질의 3D(dimension) 모델을 생성하는 기술에 대한 수요가 급증하고 있다. 이에 따라 디지털 휴먼으로 대표되는 고품질 3D 가상 인간의 제작과 관련된 다양한 기술적 시도가 이루어지고 있다. 3D 볼류메트릭 캡처는 기존의 3D 모델 생성 방식보다 빠르고 정밀한 3D 인체모형을 생성할 수 있는 기술로 각광 받고 있다. 본 연구에서는 볼류메트릭 3D 및 4D 모델 생성 분야에서 적용되는 기술들과 콘텐츠 제작의 애로사항에 대해 실제 사례를 바탕으로 3D 고정밀 페이셜 제작 기술의 분석을 시도한다. 그리고 실제 볼류메트릭 캡처를 통한 모델의 구현 사례를 바탕으로 3D 가상인간의 얼굴 제작에 대한 기술들을 고찰하고 효율적인 휴먼 페이셜 생성을 위한 그래픽스 파이프라인을 활용하여 새로운 메타휴먼을 제작하였다.

• 품질경영학회지
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• 제30권2호
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• pp.86-98
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• 2002

Defining the relationship between the quality of injection molded parts and the process condition is very complicate because of lots of factor are involved and each factor has a non-linearity. With the development of CAE(Computer Aided Engineering) technology, the estimation of volumetric shrinkage of injection mold parts is possible by computer simulation even though restricted application. In this research, Neural Network applied for finding optimal processing condition. The percent of volumetric shrinkage compared on each case and show neural network can be successfully applied selecting optimum condition not only within factor level but also between factor level.

• Journal of information and communication convergence engineering
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• 제19권3호
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• pp.180-187
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• 2021

In this paper, we present a computational volumetric reconstruction method for three-dimensional (3D) photon counting imaging with enhanced visual quality when low-resolution elemental images are used under photon-starved conditions. In conventional photon counting imaging with low-resolution elemental images, it may be difficult to estimate the 3D scene correctly because of a lack of scene information. In addition, the reconstructed 3D images may be blurred because volumetric computational reconstruction has an averaging effect. In contrast, with our method, the pixels of the elemental image rearrangement technique and a Bayesian approach are used as the reconstruction and estimation methods, respectively. Therefore, our method can enhance the visual quality and estimation accuracy of the reconstructed 3D images because it does not have an averaging effect and uses prior information about the 3D scene. To validate our technique, we performed optical experiments and demonstrated the reconstruction results.

• 대한기계학회논문집A
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• 제24권10호
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• pp.2543-2551
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• 2000

Precision injection molding is an important technology for improving productivity and lowering costs in the fields of medical components, lenses and electrical connectors. The quality of injection molded parts is affected by various processing conditions such as filling time and packing pressure profile. It is difficult to consider all the variables at the same time for prediction of the quality. In this study, the genetic algorithm was used to obtain the optimal processing conditions for minimizing the volumetric shrinkage of molded parts. For a higher convergence rate, the method of design of experiments was used to analyze the relationship between processing conditions and volumetric shrinkage of molded parts, which served as analysis tool for the capability of searching optimal processing conditions but also greatly reduces the calculation time by utilizing the information of searching area. As a practical example, compact disks that require micron-level precision were chosen for the study.