• 한국기계가공학회지
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• 제20권4호
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• pp.80-86
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• 2021

Plastics are widely used in mechanical and other fields due to their light weight, design flexibility, and molding processability. In processing plastics, defective products are mixed and reprocessed to improve production efficiency and reduce costs. In this study, an experiment was conducted to confirm the coefficient of thermal expansion of HDPE during this reprocessing. The coefficient of thermal expansion was measured at different measurement directions and heating rates. As a result, we observed that the coefficient of thermal expansion in the direction perpendicular to the injection direction is greater than that in the horizontal direction.

• 한국컴퓨터정보학회논문지
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• 제23권11호
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• pp.123-128
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• 2018

When the injection molding system molds some plastic products, defective product rate will be increased if plastic materials have some excessive moisture content. Therefore, it is very important to control the dehumidification and drying of plastic material. Since the moisture content of the plastic material may change from time to time depending on the material and the molding process, it is necessary to observe the change in real time and maintain a constant moisture content. To solve these problems, I proposed a smart factory system model for plastic molding in this paper. In addition, I designed the interface module to be installed in the dehumidifying dryer which is the core of this process. In addition to this, performance tests were conducted to check the effectiveness and the results were verified as valid.

• 항공우주정책ㆍ법학회지
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• 제20권2호
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• pp.59-158
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• 2005

현재 공군이 보유하고 있는 군용항공기가 그 설계, 제조, 사용상의 주의사항 경고 누락 등과 같은 제조상의 결함으로 인하여 인적 혹은 물적 피해가 발생한 경우, 그 책임소재를 가려 항공기 제조회사 등 법적 책임이 있는 자에게 최종적 책임을 물어야하고 이러한 점은 당해 제조상의 결함에 추가적인 사고피해로 이어지지 않는 경우에도 마찬가지이다. 또한, 보다 중요한 것은 그와 같은 책임추궁을 하기에 앞서 군용항공기의 부품이나 완성품에 애초부터 하자가 발생하지 않도록 사전에 미리 조치하는 것이다. 그럼에도 불구하고, 현재 실무상 항공기의 제조상 결함에 대한 사전 방지대책이나, 사후의 결함발생에 대한 효과적이고 명확한 대응방안이 체계적으로 제시되지 않고있다. 즉, 현재 군수물자 조달에 관한 일반 실무지침이나 협상의 기준으로 제시되는 계약서 양식 및 관련 법령 및 제도는 군용항공기의 부품적 특성, 구매방식에 따른 협상의 난이 등을 실무적 관점에서 충분히 고려한 것이라고 보기 어렵고 또한, 군용항공기 결함에 대한 책임추궁 법리 연구도 실무장의 요구를 충족시키기에는 다소 부족한 실정이다. 따라서, 군용항공기의 제조상 결함과 관련된 국가의 법적 대응방안을 미리 확보해 놓는 것이 필요한데, 여기서의 법적 대응방안이라는 것은 크게 두 가지로 구분할 수 있다. 그 하나는 군용항공기의 결함이 발생하지 않도록 판매제조업체 선정시 구매방식상의 특성을 고려하여 보다 안정적인 부품 및 완성품을 공급받을 수 있는 법적제도적 방안을 마련하는 한편, 부품에 하자가 발생할 때를 대비하여 계약시에 그 책임을 물을 수 있는 충분한 법적 장치를 설치하는 것이다. 다른 하나는 그 와 같은 노력에도 불구하고 부득이하게 제품에 하자가 발생한 사후에 있어서 책임있는 자에게 법적 책임을 추궁하기 위한 법논리를 탄탄히 갖추는 일일 것이다. 따라서, 이 글을 통해 앞으로 군용항공기를 사전에 계약함에 있어서 구매방식에 따른 문제점을 짚어본 후 그에 대한 법적제도적 개선방안을 모색하고, 또한 항공기의 결함 및 그로 인한 사고 실제로 발생한 경우 이에 대한 분쟁을 처리함에 있어서의 법적 개선점을 찾아보고자 한다. 이렇게 함으로써 장기 방위전략사업 및 대규모 국책사업 성격을 띠는 군용항공기의 구매 시에 제품의 결함율을 감소시켜 국가방위전력을 향상시킴과 동시에 추후 하자발생으로 인한 막대한 국가 및 국민의 인적 물적 손실을 방지하는데 도움을 줄 수 있다고 본다. 이 글에서는 먼저 군용항공기의 구매방식에 따른 제품결함 발생과 관련한 문제점 및 결함발생 방지를 위한 사전 개선방안을 논하고, 결함이 실제 발생한 경우의 제조회사에 대한 정부 및 피해국민의 정당한 책임추궁 방법을 군용항공기의 특성을 고려하여 논의하도록 하겠다.

• 산업경영시스템학회지
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• 제39권1호
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• pp.130-139
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• 2016

The purpose of this paper is to analyze the problems and the sources of defective products and draw improvement plans in a small plastic boat manufacturing process using TOC (Theory Of Constraints) and statistical analysis. TOC is a methodology to present a scheme for optimization of production process by finding the CCR (Capacity Constraints Resource) in the organization or the all production process through the concentration improvement activity. In this paper, we found and reformed constraints and bottlenecks in plastic boat manufacturing process in the target company for less defect ratio and production cost by applying DBR (Drum, Buffer, Rope) scheduling. And we set the threshold values for the critical process variables using statistical analysis. The result can be summarized as follows. First, CCRs in inventory control, material mix, and oven setting were found and solutions were suggested by applying DBR method. Second, the logical thinking process was utilized to find core conflict factors and draw solutions. Third, to specify the solution plan, experiment data were statistically analyzed. Data were collected from the daily journal addressing the details of 96 products such as temperature, humidity, duration and temperature of heating process, rotation speed, duration time of cooling, and the temperature of removal process. Basic statistics and logistic regression analysis were conducted with the defection as the dependent variable. Finally, critical values for major processes were proposed based on the analysis. This paper has a practical importance in contribution to the quality level of the target company through theoretical approach, TOC, and statistical analysis. However, limited number of data might depreciate the significance of the analysis and therefore it will be interesting further research direction to specify the significant manufacturing conditions across different products and processes.

• 산업경영시스템학회지
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• 제40권2호
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• pp.129-136
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• 2017

Among the information technology and automation that have rapidly developed in the manufacturing industries recently, tens of thousands of quality variables are estimated and categorized in database every day. The former existing statistical methods, or variable selection and interpretation by experts, place limits on proper judgment. Accordingly, various data mining methods, including decision tree analysis, have been developed in recent years. Cart and C5.0 are representative algorithms for decision tree analysis, but these algorithms have limits in defining the tolerance of continuous explanatory variables. Also, target variables are restricted by the information that indicates only the quality of the products like the rate of defective products. Therefore it is essential to develop an algorithm that improves upon Cart and C5.0 and allows access to new quality information such as loss cost. In this study, a new algorithm was developed not only to find the major variables which minimize the target variable, loss cost, but also to overcome the limits of Cart and C5.0. The new algorithm is one that defines tolerance of variables systematically by adopting 3 categories of the continuous explanatory variables. The characteristics of larger-the-better was presumed in the environment of programming R to compare the performance among the new algorithm and existing ones, and 10 simulations were performed with 1,000 data sets for each variable. The performance of the new algorithm was verified through a mean test of loss cost. As a result of the verification show, the new algorithm found that the tolerance of continuous explanatory variables lowered loss cost more than existing ones in the larger is better characteristics. In a conclusion, the new algorithm could be used to find the tolerance of continuous explanatory variables to minimize the loss in the process taking into account the loss cost of the products.

• 산업경영시스템학회지
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• 제40권3호
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• pp.27-37
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• 2017

As the global uncertainty of manufacturing has increased and the quality problem has become global, the recall has become a fatal risk that determines the durability of the company. In addition, as the convergence of PSS (product-service system) product becomes common due to the development of IT convergence technology, if the function of any part of hardware or software does not operate normally, there will be a problem in the entire function of PSS product. In order to manage the quality of such PSS products in a stable manner, a new approaches is needed to analyze and manage the hardware and software parts at the same time. However, the Fishbone diagram, FTA, and FMEA, which are widely used to interpret the current quality problem, are not suitable for analyzing the quality problem by considering the hardware and software at the same time. In this paper, a quality risk assessment model combining FTA and FMEA based on defect rate to be assessed daily on site to manage quality and fishbone diagram used in group activity to solve defective problem. The proposed FTA-FMEA based risk assessment model considers the system structure characteristics of the defect factors in terms of the relationship between hardware and software, and further recognizes and manages them as risk. In order to evaluate the proposed model, we applied the functions of ITS (intelligent transportation system). It is expected that the proposed model will be more effective in assessing quality risks of PSS products because it evaluates the structural characteristics of products and causes of defects considering hardware and software together.

• 품질경영학회지
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• 제49권3호
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• pp.421-431
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• 2021

Purpose: For improving outgoing quality, this study presents a novel sampling framework based on predictive analytics. Methods: The proposed framework is composed of three steps. The first step is the variable selection. The knowledge-based and data-driven approaches are employed to select important variables. The second step is the model learning. In this step, we consider the supervised classification methods, the anomaly detection methods, and the rule-based methods. The applying model is the third step. This step includes the all processes to be enabled on real-time prediction. Each prediction model classifies a product as a target sample or random sample. Thereafter intensive quality inspections are executed on the specified target samples. Results: The inspection data of three Samsung products (mobile, TV, refrigerator) are used to check functional defects in the product by utilizing the proposed method. The results demonstrate that using target sampling is more effective and efficient than random sampling. Conclusion: The results of this paper show that the proposed method can efficiently detect products that have the possibilities of user's defect in the lot. Additionally our study can guide practitioners on how to easily detect defective products using stratified sampling

• 한국산학기술학회논문지
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• 제18권10호
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• pp.531-538
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• 2017

소형 폭뢰용 수압식 신관의 품질확인은 로트에서 일정한 수량의 샘플을 꺼낸 후, 해당 샘플에 대해 작동압력을 측정하고, 사전에 설정된 합격판정기준에 따라 결함제품 개수로 로트에 대한 합부판정을 내린다. 이러한 샘플링 검사방식을 계수형 샘플링 검사방식이라고 부르며 일반적으로 가장 많이 사용되는 샘플링 검사방식이다. 그러나 이런 계수형 샘플링 검사방식은 샘플의 수가 과도하게 소요되는 경향이 있으며, 제품의 품질이 안정화 되어도 늘 같은 개수만큼의 샘플을 추출해서 시험해야 하므로 시간과 예산의 낭비를 초래한다. 본 연구에서는 작동압력시험의 데이터를 측정하여 로트의 추정불량률을 계산하고 이 값이 합격품질한계(Acceptable Quality Level) 내에 들어오는지 아닌지로 로트에 대한 합격판정을 내리는 계량형 샘플링 검사방식으로의 전환 가능성에 관한 연구를 수행하였다. 계량형 샘플링 방식으로의 변경을 통한 시료수 감소로 시험비용 절감과 계량형 데이터의 통계적 분석을 통해 불량률 추정, 공정능력지수 계산, 관리도를 활용한 품질추이 확인 등의 다양한 품질 분석을 수행할 수 있었다. 또한, 제조자 측면에서 품질문제가 발생하기 전에 사전에 품질저하를 감시하고 품질경영시스템 보완을 통한 품질개선활동의 수행 등 다양하게 활용될 수 있었다. 역시 고객인 사용자 측면에서는 품질데이터의 이력관리를 통한 과거 품질문제 추적 및 우수한 품질의 신관을 확보하는 등의 이점이 있을 것으로 기대된다.

• 디지털융복합연구
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• 제12권8호
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• pp.345-350
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• 2014

생산시스템에서의 공정계획 의사결정에 있어서 가장 중요한 의사결정은 공정을 수행할 기계를 선정하는 문제이다. 일반적으로 기계선정의 결정 기준으로는 가공에 소요되는 비용을 최소화하는 기준을 사용하고 있다. 공정을 수행할 수 있는 기계들은 각각의 고유한 가공능력에 따라 다양한 불량률을 나타내게 된다. 따라서 본 연구에서는 일반적으로 고려하는 가공비용 뿐만 아니라 불량발생 비용을 고려하여 기계를 선정하고자 한다. 본 연구에서는 기계의 가공능력에 따른 불량발생에 관한 통계학적 모델을 사용하여 가공 총비용을 최소화하는 기계선정 절차를 제시하고자 한다.

• 산업공학
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• 제25권1호
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• pp.40-51
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• 2012

Today, many manufacturing companies realize that collaboration is crucial for their survival. Especially, in the perspective of quality, the importance of collaboration is emphasized because economic loss increases exponentially while defective parts go through the process in supply chain. However, the manufacturing companies are facing two main difficulties in implementing collaborative relationships with their suppliers. First, it is difficult for the suppliers to produce reliable products due to their obsolete facilities. The problem gets worse for second- or third-tire vendors. Second, the companies experience the lack of universally understandable set of terminology and effective methodologies for knowledge representation. Ontology is one of the best approaches to expressing and processing a domain knowledge. In this paper, we propose the manufacturing ontology-based quality prediction framework to represent and share the knowledge of industrial environment and to predict product quality in manufacturing processes. In addition, we develop the ontology-based quality prediction system based on the proposed framework. We carried out a series of experiments for an injection molding process at an automotive part supplier. The experimental results demonstrated that the proposed framework and system can be successfully applicable in manufacturing industry.