CAD

Spiral bevel gears are essential components of mechanical devices; however, it is difficult to design, manufacture, and in-spect them because their shapes are difficult to model on a computer. In this study, a method for modeling spiral bevel gears manufactured using a Gleason machine was investigated. The method to generate a gear tooth profile as point data and calcu-late transformation matrices between coordinate systems based on the machining process is explained in detail. The cutting volume is determined using multiple cross-sectional profiles created along the tool path, and the final gear shape is generated by subtracting the cutting volume from the workpiece. A spiral bevel gear modeling system is developed based on the pro-posed method, and its reliability is verified by measuring the actual gear and comparing it to the modeled shape. The verifica-tion results indicated that the modeled shape showed a 7.1 μm difference from the sample gear, implying that the proposed modeling method is reliable for modeling spiral bevel gears.

In this paper, we propose an integrated design system that incorporates the design history, information and intent to support an improved design. Current CAD systems are powerful in representing the shape of a product, but they do not carry the design information that has been used or created in designing the product. We propose an integrated design system to enable the storage and usage of design information in addition to shape manipulation. We define an entity called Element Object that could represent a mechanical element, a sub-assembly or an assembly by using object-oriented methodology together with the related design information. The Element Object can represent a variety of information such as design parameters, documents, catalogues, functions, and behaviors. A mailing system is constructed among Element Objects to assist a collaborative design. We also introduce an Evolutionary Design Method using a genetic algorithm. By using the proposed design system, we could manage design information and relation systematically. This contributes to an improved design. It reduces design time and errors at both initial design and re-design. Its capability and efficacy is observed particularly during the re-design process.

The view dependency of typical z-buffer-based NC simulation methods is overcome by a polygon rendering technique that generates polygons to represent the workpiece, thus enabling dynamic viewing transformations without reconstruction of the entire data structure. However, the polygon rendering technique still has difficulty in realising real-time simulation owing to the limited performance of current graphics devices. There-fore, it is necessary to develop a mesh decimation method that enables rapid rendering without loss of display quality. To meet this requirement, in this paper, a new mesh decimation algorithm is proposed for a workpiece which is represented by the z-map structure and whose shape is dynamically changed by the tool. In this algorithm, the z-map data for the workpiece are divided into several regions, and a triangular mesh is constructed for each region. Then, if the tool cuts any region, its mesh is regenerated and decimated again. Since the range of mesh decimation is confined to a few regions, the reduced triangles for rapid rendering can be obtained in a short time. This local mesh decimation method may contribute toward realising the polygon rendering-based NC simulation in real-time on computers equipped with general graphics cards.

Design parameters and goals play important roles in design. Design goals are the required functions of the design elements and are explicitly expressed by design parameters. Design parameters also indicate the relations among design elements, by which a constraint network can be constructed and some useful information can be induced. In this study, the mechanical design process is viewed to be the assignment of design goals and their realization through the evolutionary refinement of the design parameters. The design activities are processed on traditional computer-aided design systems by specifying the shapes of the design elements. Thus, an integrated design system based on the computer-aided design system is proposed to assign the design goals and refine the values of the design parameters along the design process. The proposed design system also provides some useful facilities to a designer such as the construction of a constraint network, an evolutionary design method and a re-design plan.

We propose a feature-based multi-resolution representation of B-rep solid models using history-based Boolean operations based on the merge-and-select algorithm Because unfon and subtraction are commutative in the history-based Boolean operations, the integrity of the models at various levels of detail (LOD) is guaranteed for the reordered features regardless of whether the features are subtractive or additive The multi-resolution solid representation proposed in this paper includes a non-manifold topological merged-set model of all feature primitives as well as a feature-modeling tree reordered consistently with a given LOD criterion As a result, a B-rep solid model for a given LOD can be provided quickly, because the boundary of the model is evaluated without any geometric calculation and extracted from the merged set by selecting the entities contributing to the LOD model shape

The requirements of multi-resolution models of feature-based solids, which represent an object at many levels of feature detail, are increasing for engineering purposes, such as analysis, network-based collaborative design, virtual prototyping and manufacturing To provide multi-resolution models for various applications, it is essential to generate adequate solid models at varying levels of detail (LOD) after feature reanangement, based on the LOD criteria However, the non-commutative property of the union and subtraction Boolean operations is a severe obstacle to arbitrary feature rearrangement To solve this problem we propose history-based Boolean operations that satisfy the commutative law between union and subtraction operations by considering the history of the Boolean operations Because these operations guarantee the same resulting shape as the original and reasonable shapes at the intermediate LODs for an arbitrary rearrangement of its features, various LOD criteria can be applied for milti-resolution modeling in different applications

In graduate class, education on shortening the lead-time in designing and developing products by various computer-aided systems in a network and applying virtual engineering was carried out. To accomplish such a purpose, network based education about engineering design was applied. Some laboratories consisting of various computer-aided systems were constructed and connected by a network. A sample project to develop a radio controlled (R/C) was carried out in order to practice the design of a product based on network based technologies. While students were doing the sample project, they had experienced how to use various computer-aided systems efficiently in a network for concurrent engineering and how to apply the technology of virtual engineering.

Axiomatic design is a powerful tool for in designing a product and describes functional requirements (FRs) and design parameters (DPs). In this paper, we extended axiomatic design by introducing shapes and databases. We used functional geometric features (FGFs) for the shape of DP. The databases store links of FR-DP-GE and their hierarchies. The retrieval of proper FGFs from the database is performed by matching a query FR with stored FRs linked to the corresponding FGFs by a lexical search based on the frequency of words and the sequence of the words in the FR statements using a synonym checking system. A computer algorithm automatically combines and assembles the retrieved FGFs. Genetic algorithm (GA) searches for the best matching of interface types between FGFs and generates the corresponding assembly sequences based on the codes of the chromosomes. Geometric interface-ability between FGFs is calculated as a value of INTERFACE_metric. The higher value of INTERFACE_metric means better the design solution for the given FRs that must be satisfied in the sense of language and geometric interface matching.

In this research, a method is presented for generating a deformed model satisfying given error criteria from an STL model in a triangular-mesh representation suitable for rapid prototyping (RP) processes. A deformed model is a non-uniformly modified shape from a base STL model. In developing a family product with various sizes such as a shoe, sometimes prototypes for all sizes should be made using an RP machine. Although an STL model is generated from a solid model, it is well known that creating a non-uniformly modified solid model from a base solid model is very difficult. Generally there are some gaps between surfaces after modification, and stitching the gaps is very difficult. To solve this problem, the authors explored the possibility of generating a deformed STL model directly from a base STL model. This research includes a data structure for modifying the STL model, checking the error of a modified edge compared with the exact non-uniformly scaled curve, checking the error of a modified facet compared with the exact non-uniformly scaled surface, and splitting a facet with an error greater than the allowable tolerance. Using the results of this research, the difficult work of creating solid models to build non-uniformly deformed STL models could be avoided.

From a global perspective, Korea is a leader in the field of indoor screen golf technologies. However, some products and technologies that are being used in current indoor screen golf systems have shortcomings with regard to technical stability. Nowadays, hydraulic actuators are widely used in golf swing plate systems to adjust the plate and recreate for the player the slope of the terrain shown on the screen. However, the hydraulic actuators used in screen golf systems have disadvantages associated with them, such as oil leakage, bad control, and high price. To address what we perceive to be a shortage of existing alternatives, we developed a golf swing plate that uses screw actuators to drive the swing plate up and down. We take the opportunity in this study to perform an analysis of the kinematic behavior of our design employing three active PRS (Prismatic joint–revolute joint–spherical joint) legs that provide the golf swing plate with three degrees of freedom. In this paper, we focus on the derivation of kinematic equations and constraints related to kinematic variables. Furthermore, we derive the amount of translation necessary for each prismatic joint to achieve the motions required of the golf swing plate. We go on to verify the complex movement of the swing plate using the NX motion simulation program. Finally, we construct a prototype and test the functions of the golf swing plate.

이 논문에서는 기계요소설계 강의에서 사용한 교육 기자재에 대한 분석을 하였다. 기자재로는 멀티미디어 자료와 플라스틱 모형, 단면 절개 모형, 상용 기계요소설계 프로그램을 사용하였으며, 이러한 기자재들에 대해 기자재의 준비 용이성과 강의실에서의 사용 수월성, 기계요소를 설명하기 위한 편의성, 강의실로의 이동 편의성, 현실감, 사용 안전성, 비용, 학생들의 만족도 등의 관점에서 분석하였다. 가장 널리 사용하는 멀티미디어 자료는 많은 측면에서 다른 기자재들보다 우수하다고 분석되었으며, 플라스틱 모형은 기계요소를 설명하기 위한 편의성 측면에서, 단면 절개 모형은 현실감을 주는 측면에서 우수하다고 분석되었다. 그리고 상용 기계요소설계 프로그램은 학생들이 사용하기 불편하였으나, 자신의 설계 결과를 검증할 수 있어 학생들이 만족하였다.

스탬핑 프로세서는 고생산성과 낮은 가격으로 인해 자동차 차제나 항공기 부품, 그리고 전자제품 등 다양한 장치에 널리 이용된다. 최근에 에너지 산업과 연관되어 연료전지 분리판, 열교환기 등에 사용되는 주름구조를 가지는 박판의 응용이 급속히 증가되고 있다. 그러나 복잡한 형상 때문에 주름구조물을 한번의 성형으로 만들기가 매우 어렵다. 따라서 본 연구에서는 다단성형공정을 이용하여 성형성을 향상시키는 방법을 제안하였다. 1 차 박판성형 후 열처리를 통하여 가공경화 부분을 제거하고 다시 성형하는 방법으로 복잡하고 실용성이 높은 박판구조물 제작이 가능하도록 하였다. 본 연구에서는 제안한 방법을 검증하기 위하여 판형 열교환기에 응용이 가능한 두께 100 µm를 가지는 박판주름구조를 제작하고 공정변수를 연구하였다. Abstract: The stamping process is widely used in fabricating various sheet-parts for vehicle, airplane, and electronic devices due to its low processing cost and high productivity. Recently the use of thin sheets with corrugated structures has rapidly increased for the production of energy devices, e.g., heat exchangers and fuel cells. However, it is very difficult to make corrugated structures directly in the stamping process due to their geometrical complexity. To solve this problem, this paper proposes a multi-step stamping process with a combined heat treatment process: a sequence of the first stamping, heat treatment, and second stamping. By multi-stamping, we obtained successful results in fabricating very thin corrugated structures with thicknesses of 100 µm; these are applicable as part of a plate-type heat exchanger.

A V belt pulley is widely used in automotive industry. More than four pulleys in one automobile are used, such items as crankshaft, water pump, air-con compressor and power steering pump. Although the shape and usage of pulleys are very simple, the design evaluation of a pulley design is difficult because the load conditions and the installation environment are complicated. So, we formulated the design evaluation for the V belt pulley by using CAE system, which enables to develop a design automation system. By using this system, an engineer can evaluate a pulley design easily without any painstaking effort, such as consideration of the complicated loads and CAE activities. Also the system helps to accumulate the design experience of a company, which guides the optimum design based on experience.

This paper introduces the development of a three-dimensional jig design system for automotive body welding assembly. Recently, three-dimensional CAD systems have been introduced in the jig design area, because they reduce errors in design process and the design result can be used readily for virtual manufacturing simulation. However, to facilitate three-dimensional jig design, it is essential to customize three-dimensional CAD system for this specific design area. To accomplish this object, we first standardized the parts and units in a jig assembly, and then built the standard part library. We also developed the dedicated 3D design capabilities of jig units and a jig base. By using this system, design can be performed more intuitively, and verification and simulation of design results can be done more easily. The proposed system has been implemented using the UG/Open API of the Unigraphics system.

In this paper, we explain the DMU (digital mockup) system based on the PDM system. Most manufacturing companies are trying to develop a competitive product by increasing the quality, shortening time to market (TTM) and reducing the cost of a product. Some technologies such as SE (System Engineering), CE (Concurrent Engineering), QFD (Quality Function Development), CI (Cost Innovation) and some systems such as CAD (Computer-Aided Design), CAE (Computer-Aided Engineering), CAM (Computer-Aided Manufacturing), PDM (Product Data Management) and visualization system are adopted for these purposes. Specially, DMU system utilizes a visualization system that shows the 3D shape of a product on the computer and it gives a quick intuition to a person whether he/she is an engineer or not. It also can induce the effects of CE and QFD. So, D company is developing a DMU system integrating CAD, visualization and PDM system. The main feature of the developed DMU system is that it is entirely integrated with PDM system, which means that the 3D shape of any part or assembly can be retrieved through PDM system. The DMU system will change the development process, which will increase the competitiveness of a developed product.

CAMPform2D is a Finite Element Method (FEM) based process simulation system designed to analyze two dimensional (2D) flow of various metal forming processes. It enables designers to analyze metal forming processes on the computer rather than the shop floor using trial and error and provides vital information about material and thermal flow during the forming process to facilitate the design of products. CAMPform2D can be used by companies, research institutes and industrial applications to analyze forging, extrusion, drawing, heading, upsetting and many other metal forming processes. Also, process simulation using CAMPform2D can be instrumental in cost, quality and delivery improvements at leading companies. Today's competitive pressures require companies to take advantage of every tool for rapid manufacturing of well-designed product. So, the preprocessor of simulation program must be easy to use to speed-up design. In this paper, we introduce new version of Preprocessor and show how easy to use it. And, Preprocessor will prove itself to be easy and extremely effective.

CAMPform2D is a Finite Element Method (FEM) based process simulation system designed to analyze two dimensional (2D) flow of various metal forming processes. It enables designers to analyze metal forming processes on the computer rather than the shop floor using trial and error and provides vital information about material and thermal flow during the forming process to facilitate the design of products. CAMPform2D can be used by companies, research institutes and industrial applications to analyze forging, extrusion, drawing, heading, upsetting and many other metal forming processes. Also, process simulation using CAMPform2D can be instrumental in cost, quality and delivery improvements at leading companies. Today's competitive pressures require companies to take advantage of every tool for rapid manufacturing of well-designed product. So, the preprocessor of simulation program must be easy to use to speed-up design. In this paper, we introduce new version of Preprocessor and show how easy to use it. And, Preprocessor will prove itself to be easy and extremely effective.

This paper introduces a project for the development of an F-125 machine using 3D PLM systems including 3D CAD, CAM, CAE, PDM, and DMU systems. Here, the F-125 machine is a formula racing car equipped with a 125cc motorcycle engine. A development process and computer-integrated environment was established using 3D PLM systems on the conceptual basis of concurrent and virtual engineering. A DMU model for a full vehicle was built using CATIA V.5 and used to check interference between parts and to simulate assembly process. This DMU-based approach enables to find and fix manufacturing problems in the early design stage. All development activities have been done by the graduate and undergraduate students of the automotive engineering department of Kookmin University. Through the project, the students could acquire knowledge about car development process and 3D PLM systems in automotive industry.

This paper describes the parting and Boolean operations for a pseudo-solid model of a plastic part, and their application to injection mold design. Here, a pseudo-solid model means a sheet model that looks like a solid model, but its boundary is not closed. When a solid model created in a different CAD system is imported through a standard data exchange file format, in most cases, a pseudo-solid model may be created due to tolerance or some other problems. However, most existing mold design systems based on solid modeling kernels require a complete part solid model. Therefore, mold designers have to do time-consuming healing operations to convert a pseudo-solid to solid. To eliminate or reduce the healing pre-process for mold design, in this paper, we proposed the parting and Boolean Operations on pseudo-solid part models. This paper also describes their detailed implementations and a case study.

체계 요구조건에 빠르고 정확한 자료제공을 위해 고체추진기관 구조체에 대한 설계자동화 프로그램인 “ProDes”를 개발하고 검증하여 그 성능을 입증하였다. 주어진 체계설계 요구도 및 구속조건으로부터 총 개발기간과 인력을 획기적으로 감소시키며, 또 설계, 해석, 시뮬레이션 및 도면화 등 일련의 업무를 통합적으로 수행하기 위해 프로그램 개발이 수행되었다. 프로그램은 모듈화되어 있으며, 각 단계별 계산은 설계 변수별 적용연구가 수행되어 최종 설계 목표치에 도달되도록 구성 되어있다. 다양한 종류의 마스터 모델로 된 구성품과 체결형태는 구축된 라이브러리 DB 모듈로부터 얻어진다. 개발 프로그램을 이용한 추진기관 구조체 설계와 기존 상세된 설계를 비교 분석한 결과 서로 잘 일치함을 확인하였다. In order to perform system requirements quickly and accurately, an automatic design program of solid rocket motors(SRM) structure designated as the "ProDes software" has been developed and verified. From given system design criteria and constraints, it has the capabilities to design, analysis, simulation and drawing process to greatly reduce the over "design cycle time" and manpower of a project. The conception of the program is modular, and calculations are performed step by step allowing parametric design studies and providing final selected design goal. Each configurations of SRM components and joint types composed of various master models is obtained from the data base module of the library. Between the design results of the ProDes software and those of the previous detail design of the established motor showed good agreements.

We developed a design automation system to reduce the lead time and help engineers in designing a solid fuel, or a grain, for rocket missiles. First, we analyzed design activities and shapes of a grain, which resulted in the standard of design process and shape. We decided development process which consisted of two typical activities such as constructing master library and implementing design system. We constructed some master models for typical external shapes and core shapes of grains which were used in modeling the shape of a designing grain. Also we implemented a design automation program to use the master models according to the pre-defined design process. It can calculate some design parameters such as mass, mass center, volume and combustion area that are used in analyzing a proposed grain. Finally, we could reduce the design time dramatically and increase design quality by automating many routine and difficult works. We developed a design automation system to reduce the lead time and help engineers in designing a solid fuel, or a grain, for rocket missiles. First, we analyzed design activities and shapes of a grain, which resulted in the standard of design process and shape. We decided development process which consisted of two typical activities such as constructing master library and implementing design system. We constructed some master models for typical external shapes and core shapes of grains which were used in modeling the shape of a designing grain. Also we implemented a design automation program to use the master models according to the pre-defined design process. It can calculate some design parameters such as mass, mass center, volume and combustion area that are used in analyzing a proposed grain. Finally, we could reduce the design time dramatically and increase design quality by automating many routine and difficult works.

체결류는 일반 제품을 설계할 때 널리 사용되며, 일반 부품에 비하여 표준화가 잘 되어 규격화 되어 있다는 특징이 있다. 그래서 체결류를 설계할 때에는 먼저 수식을 사용하여 원하는 기능을 가진 체결류를 계산하고, 최종 사양은 규격에서 계산된 용량을 만족하는 것을 선택한다. 이 연구에서는 이러한 체결류 설계의 특징을 살리며 삼차원 CAD 시스템에서 편리하게 체결류 설계를 할 수 있는 시스템에 대한 연구를 수행하였다. 이 시스템에서 자동으로 설계하기에 적합한 체결류 형상을 정의하였으며, 체결류 설계에 필요한 설계 인자와 형상 치수를 규격에서 추출하여 데이터베이스를 구축하였다. 또한 체결류를 설계할 때 사용하는 설계식을 구현하여 설계식의 입력 인자와 출력 인자를 규격으로부터 추출한 데이터베이스 및 형상 치수와 연결시켰다. When we design a product, we spend a considerable amount of time in designing fasteners and their mating parts. Fasteners have special features because of which they are widely used and well standardized. Although we use some equations to design the fasteners, we should select these fasteners from the standardized table. In order to design them quickly using the CAD system, we proceeded as follows. First, we prepared some standardized shapes of fasteners to design them automatically. Next, we built a database of some fasteners such as a tension bolt, lock wire, thread, pin, and snap ring. Then, we used the design equations to quickly and precisely calculate the various parameters. Finally, we used a configuration design method to generate the shapes automatically using the results of the calculation and the values retrieved from the database. We applied this approach to the design of a propulsion structure, and demonstrated that this approach worked well and saved considerable time.

In this research, we developed a design system for a compressor of an air conditioner using solid CAD system. The developed design system has some characteristics. First, the design system used a configuration design method, so a designer can design a compressor very quickly by using the constructed master libraries. Next, the system was developed to be used not only by engineers but also by salesmen. It is very easy for a user to use it, so a salesman can get a result very easily with the design system. And it has some design modules which give a considerable convenience to designers. Actually, designers are accustomed to the module based design. Then, it has calculation and analysis functions. Volume and mass of a part, and interference between parts are calculated by using the geometric calculation function of a solid CAD system. Also a packaging calculation was implemented to get the smallest space to package compressors for transportation and storing. An interface with a program to analyze the vibration of a compressor was developed in this design system. The design system is similar to CBD (Case-Based Design) system in the view of the whole design process.

In this paper, we proposed a data structure to represent structural components of solid rocket motors (SRM) in an automated design program. To propose the data structure, we searched the necessary functions for the automated design program should have. In order to design the structural components of solid rocket motors sufficiently with a design program, it should have the functions to represent the shapes of the components, the drawing and analysis models, the design variables, various product structures, interferences, characteristic properties, design equations,and tightening sets. By modifying the data structure of an element object that is a general purpose data structure to represent a general component of a product, a new data structure was proposed to satisfy all the necessary functions with optimum. Finally, a design program for the structural components of solid rocket motors was developed successfully with the proposed data structure.

In developing a tire, many CAE analyses are performed to make a better tire. But its meshing work is not easy, and it takes much time. One of the reasons of taking much time is that there are many overlapped geometric entities in CAD data that are modeled in CAD system by CAD engineers. In this study, we studied about the features of the overlapped geometric entities, and the method to find out and delete them. I developed a program using the proposed algorithm, and applied it in meshing tire pattern and tire case. I proved that the time in meshing a tire reduced dramatically by removing overlapped geometric entities by using the developed program.

이 연구에서는 스퍼 기어의 치형이 생성되는 이론을 정리하고, 이를 이용해 산업계에서 실제 사용되는 스퍼 기어 자동 모델링 시스템을 개발하였다. 기어 치형은 크게 이끝원, 이뿌리원, 필렛 곡선, 인벌류트 곡선 등 네 개의 곡선으로 이루어진다. 이 연구는 이러한 네 개의 곡선 생성에 대한 이론적인 근거를 제시하고, 이론적인 치형에서 백래시, 치형 수정, 크라우닝 등이 있는 실제로 사용되는 치형에 대한 이론 전개를 한 후 치형을 모델링하는 시스템을 구현하였다. 기존에는 기어 치형 전체를 체계적으로 생성하기 위한 이론 정리가 잘 되어 있지 않고, 특히, 백래시, 인벌류트 치형 수정, 크라우닝을 반영하는 치형 모델링에 대한 연구가 없어 실제 사용되는 기어를 정확하게 모델링하기 어려웠다. 이 연구로 가장 형상이 까다로운 기계 요소인 기어에 대한 모델링 기술이 발전할 것으로 기대한다. 또한, 이 연구는 스퍼 기어 뿐 아니라 헬리컬 기어, 베벨 기어, 스파이럴 베벨 기어의 실질적인 치형을 생성하는 연구에 대한 기초가 될 것으로 기대한다. Based on the theory of generating the practical tooth profile of spur gears, I implemented a spur gear modeling system. Gear teeth are composed of four curves: tip circle, root circle, fillet curve, and involute curve. This paper presents the theoretical basis for the generation of these four curves. Based on the knowledge of the actual gear profile with backlash, profile modification, and crowning, I implemented a modeling system of practical spur gears. The generation of a whole tooth profile has not been well organized in the earlier studies. In particular, a lack of study on gear modeling that reflects backlash, profile modification, and crowning makes it difficult to accurately model the gears that are actually used in the industry field. This study is expected to enhance the modeling technology for gears that have the most difficult shape among mechanical elements. In addition, this study is expected to serve as the basis for the study of modeling a practical tooth profile of spur gears, helical gears, bevel gears, and spiral bevel gears.

With the development of computers, CAE is widely used. Generally, after a shape is created in CAD system and it is used to create meshes for CAE. Sometimes when you try to modify meshes, there is a case that you cannot modify them because there is no original CAD data. In this case, there is a need to modify the meshes directly, and this study is about how to modify CAE meshes directly without linking them with the original CAD model. Currently, most of the methods for directly modifying meshes are to select and move nodes respectively, and when there are many meshes to be modified, it takes a lot of time and it is difficult to modify them accurately. In this study, planar or cylindrical surfaces are created by using nodes in meshes, and then the nodes move on the changed surfaces by the rounding, filleting and draft operations. Most of the mechanical parts are planar or cylindrical surfaces, so the results of this study can be widely applied to CAE of mechanical parts.