• International Journal of Automotive Technology
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• 제4권4호
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• pp.193-201
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• 2003

The problem of brake judder is typically caused by defects of quality manufacturing. DFSS (Design for six sigma) is a design process for quality improvement. DFSS will result in more improved but less expensive quality products. This paper presents an implementation of DFSS for quality improvement of the brake judder of heavy-duty trucks. Carrying out 5 steps of DFSS, the major reasons for defects of quality are found. The numerical approximation of the brake system is derived by means of the response surface method. Its quality for brake judder is improved by using the sigma based robust design methodology. Results are compared between the conventional deterministic optimal design and the proposed sigma based robust design. The proposed one shows that manufacturing cost may increase as the quality level increase. The proposed one, however, is more economical in aspect of the overall cost since the probability of failure dramatically goes down.

• 한국공작기계학회논문집
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• 제15권5호
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• pp.65-71
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• 2006

This paper presents the robust design of gripper part for a high-speed LCD(Liquid Crystal Display) transfer system. In this paper, the $1^{st}$ DOE(Design of Experiment) is conducted to find out main-effect factors for the design of gripper part. Thirty-six analysis are performed using $ANSYS^{(R)}$ and their results are statistically analyzed using $MINITAB^{(R)}$, which shows that the factors, i.e., First-width, Second-width, Rec-width, and thickness of gripper part, are more important than other factors. The main effect plots shows that the maximum deflection and mass of gripper part are minimized by increasing First-width, Second-width, Rec-width and thickness. The $2^{nd}$ DOE is conducted to obtain RSM(Response Surface Method) equation. The CCD(Central Composite Design) technique with four factors is used. Optimum design is conducted using the RSM equation. Genetic algorithm is used for optimal design. Six sigma robust design is conducted to find out a guideline for control range of design parameter. To obtain six sigma level quality, the standard deviations of design parameters are shown to be controlled within 5% of average design value.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2005년도 추계학술발표대회 논문집
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• pp.211-214
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• 2005

This research studied robust design of composite structure under combined loading of bending and torsion. DOE (Design of Experiment) technique was used to find important design factors. The results show that the beam height, beam width, layer thickness and stack angle of outer-layer are important design parameter. The $2^{nd}$ DOE and RSM (Response Surface Model) were conducted to obtain optimum design. Multi-island genetic algorithm was used to optimum design. An approximate value of 6.65 mm in deflection was expected under optimum condition. Six sigma robust design was conducted to find out guideline for control range of design parameter. To acquire six sigma level reliability, the sigma level reliability, the standard deviation of design parameter should be controlled within 2.5 % of average design value.

• 대한기계학회논문집A
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• 제33권10호
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• pp.1132-1138
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• 2009

The spring constants of primary suspensions for a railway vehicle are optimized by a robust design process, in which the response surface models(RSMs) of their dynamic responses are constructed via the design of experiment(DOE). The robust design process requires an intensive computation to evaluate exactly a probabilistic feasibility for the robustness of dynamic responses with their probabilistic variances for the railway vehicle. In order to overcome the computational process, the process capability index $C_{pk}$ is introduced which enables not only to show the mean value and the scattering of the product quality to a certain extent, but also to normalize the objective functions irrespective of various different dimensions. This robust design, consequently, becomes to optimize the $C_{pk}$ subjected to constraints, i.e. 2, satisfying six sigma. The proposed method shows not only an improvement of some $C_{pk}$ violating the constraints obtained by the conventional optimization, but also a significant decrease of the variance of the $C_{pk}$.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2006년도 춘계학술대회 논문집
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• pp.361-362
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• 2006

This paper presents the robust design of gripper part for a high-speed LCD (Liquid Crystal Display) transfer system. In this paper, the 1st DOE (Design of Experiment) is conducted to find out main-effect factors fur the design of gripper part. Thirty-six experiments are performed using $ANSYS^{(R)}$ and their results are statistically analyzed using $MINITAB^{(R)}$, which shows that the factors, i.e., First-width, Second-width, Rec-width, and thickness of gripper part, are more important than other factors. The main effect plots shows that the maximum deflection and mass of gripper part are minimized by increasing First-width, Second-width, Rec-width and thickness. The 2nd DOE is conducted to obtain RSM (Response Surface Method) equation. The CCD (Central Composite Design) technique with four factors is used. Optimum design is conducted using the RSM equation. Genetic algorithm is used for optimal design. Six sigma robust design is conducted to find out a guideline for control range of design parameter. To obtain six sigma level reliability, the standard deviations of design parameters are shown to be controlled within 5% of average design value.

• 한국산학기술학회논문지
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• 제7권2호
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• pp.101-106
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• 2006

본 연구에서는 통계적 파괴 분석으로서 turbine blade에서의 피로 수명이 최소화되는 최적 설계안을 도출하는 데에 있다. 그 방법으로서는 최소한의 피로 수명이 나오는 설계안을 위해 먼저 fillet radius를 고정한 후, 실험 계획법을 통하여 turbine blade에서의 최적의 X 와 Y 위치를 찾는다. 또한 six sigma analysis로서 X 와 Y 인자에서의 공정에 대한 불확실성을 계산한다. 그리고 robust design을 사용하여 주어진 불확실성 상태에서 최적의 fillet radius 값을 결정하여 최대의 von Mises 응력은 20%가 작아지고 피로수명이 두 배가 되는 최적의 설계를 할 수가 있었다.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2005년도 추계학술대회 논문집
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• pp.869-872
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• 2005

This research studied robust design of column part for LCD transfer system. $1^{st}$ DOE(Design of Experiment)was conducted to find out main effect factors. 36 experiments were performed and their results were shows that the geometric parameters(Low-length, Side-length, Upper-thickness, Middle-thickness)are more important than other factors. The main effect plots shows that the maximum deflection of column is minimized with increasing Low-length, Side-length, under-thickness and Middle-thickness. $2^{nd}$ DOE was conducted to obtain RMS(Response Surface Method)equation 25 experiments were conducted. The CCD(Central Composite Design)technique with four factors were used. The coefficient of determination $(R^2)$ for the calculated RSM equation was 0.986. Optimum design was conducted using the RSM equation Multi-island genetic algorithm was used to optimum design. Optimum value for Low-length. Side-length, Upper-thickness and Middle-thickness were 299.8mm, 180.3mm, 21.7mm, 21.9mm respectively. An approximate value of 5.054mm in deflection was expected to be a maximum under the optimum conditions. Six sigma robust design was conducted to find out guideline for control range of design parameter. To acquire six sigma level reliability, the standard deviation of design parameter should be controlled within 2% of average design value.

• 대한기계학회논문집A
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• 제29권3호
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• pp.455-461
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• 2005

This research studied robust design of composite hand for LTR (LCD glass Transfer Robot). $1^{st}$ DOE (Design of Experiment) was conducted to find out vital few Xs. 108 experiments were performed and their results were statistically analyzed. Pareto chart analysis shows that the geometric parameters (height and width of composite beam) are more important than material parameters $(E_{1},\;E_{2})$ or stacking sequence angle. Also, the stacking sequence of mid-layer is more important than that of outer-layer. The main effect plots shows that the maximum deflection of LTR hand is minimized with increasing height, width of beam and layer thickness. $2^{nd}$ DOE was conducted to obtain RSM (Response Surface Method) equation. 25 experiments were conducted. The CCD (Central Composite Design) technique with four factors was used. The coefficient of determination $(R^{2})$ for the calculated RSM equation was 0.989. Optimum design was conducted using the RSM equation. Multi-island genetic algorithm was used to optimum design. Optimum values for beam height, beam width, layer thickness and beam length were 24.9mm, 186.6mnL 0.15mm and 2402.4mm respectively. An approximate value of 0.77mm in deflection was expected to be a maximum under the optimum conditions. Six sigma robust design was conducted to find out guideline for control range of design parameter. To acquire six sigma level reliability, the standard deviation of design parameter should be con trolled within $2{\%}$ of average design value

• 한국공작기계학회논문집
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• 제15권4호
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• pp.8-14
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• 2006

The important function of Ball-Stop part is to operate power shift using suitable pneumatic force for vehicle with more than 5 ton when a driver changes gear. In this paper, we have applied the concept of the DFSS(Design for Six Sigma) to robust design of Ball-Stop part. First, we have found the control factors which could mainly influence the performance of the Ball-Stop part. The simulations of contact between head and detent pin was performed to evaluate effect of control factors according to DOE(Design of experiment) by using $ADAMS^{(R)}$. Finally, we have obtained optimal levels of each factors using $MINITAB^{(R)}$. Through the comparison of the result of optimized design with one of inintial design, we have verified the usefulness of DFSS method which can be applied to robust design of mechanical systems.

• Industrial Engineering and Management Systems
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• 제11권4호
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• pp.346-352
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• 2012

While systems engineering has been widely applied to complex system development, some evidences are reported about major budget and schedule overruns in systems engineering applied. On the other hand, many organizations have been deploying Design for Six Sigma (DFSS) to build Six Sigma momentums in the area of design and development for their products and processes. To explore the possibility of having a DFSS complement systems engineering process, this process reviews the systems engineering with their categories of effort and DFSS with its methodologies. A comparison of the systems engineering process and DFSS indicates that DFSS can be a complement to systems engineering for delivering higher quality products to customers faster at a lower cost. We suggest a simplified framework of systems engineering process, that is, PADOV which was derived from the generic systems engineering process which has been applied to the development of T-50 advanced supersonic trainer aircraft by Korea Aerospace Industries (KAI) with technical assistance of Lockheed Martin. We demonstrated that each phase of PADOV framework is comprehensively matched to the pertinent categories of systems engineering effort from various standards.