• 품질경영학회지
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• 제16권1호
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• pp.59-66
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• 1988

On-line QC by Taguchi has two approaches of: the cost-oriented (cost-emphasis) QC and the process-oriented (quality-emphasis) QC. The main concern of this paper is to estabilish and recommend a desirable one as a QC target. Simulation is employed to solve the question, and the failure cost (A), appraisal cost (B), and prevention cost (C) are adopted as decision variables. In conclusion, the process-oriented QC is the recommendable approach as far as there is no remarkable cost difference between the two approaches and possible to apply on.

• 산업경영시스템학회지
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• 제41권1호
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• pp.110-117
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• 2018

Machines and facilities are physically or chemically degenerated by continuous usage. One of the results of this degeneration is the process mean shift. By the result of degeneration, non-conforming products and malfunction of machine occur. Therefore a periodic preventive resetting the process is necessary. This type of preventive action is called 'preventive maintenance policy.' Preventive maintenance presupposes that the preventive (resetting the process) cost is smaller than the cost of failure caused by the malfunction of machine. The process mean shift problem is a field of preventive maintenance. This field deals the interrelationship between the quality cost and the process resetting cost before machine breaks down. Quality cost is the sum of the non-conforming item cost and quality loss cost. Quality loss cost is due to the deviation between the quality characteristics from the target value. Under the process mean shift, the quality cost is increasing continuously whereas the process resetting cost is constant value. The objective function is total costs per unit wear, the decision variables are the wear limit (resetting period) and the initial process mean. Comparing the previous studies, we set the process variance as an increasing concave function and set the quality loss function as Cpm+ simultaneously. In the Cpm+, loss function has different cost coefficients according to the direction of the quality characteristics from target value. A numerical example is presented.

• 유통과학연구
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• 제17권4호
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• pp.51-57
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• 2019

Purpose - This study aims to improve the distribution structure of the OLED market and develop cost-effective optimization techniques. Specifically, it is a study on the optimization of ferric chloride to improve the etch of SUS MASK for OLED. Research design, data, and methodology - Applying the optimal conditions of the experiment, the final confirmation was evaluated for improvement by the Process Capability Index (Cpk). It is possible to derive social performance such as improvement of precision of SUS MASK manufacturing, economic performance such as defect rate, reduction of waste generation and treatment cost, technological achievement such as SUS MASK production technology, improvement of profit structure of technology development and process improvement do. Results - The improvement of the Cpk before the improvement was made was confirmed to be 0.57% with a defect estimate of 25.07% with a failure estimate of 0.57% after the improvement, and 8.84% with a failure estimate of 0.57% level after the improvement. Conclusions - If the conclusions obtained from the specimen experiment are applied to the manufacturing process of SUS MASK, it will be possible to expect excellent cost-effective competitiveness due to the improvement of precision and reduction of defect rate to enhance the OLED market penetration.

• 대한산업공학회지
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• 제37권4호
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• pp.390-399
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• 2011

Generally the life-cycle cost of complex systems composed of several sub systems or equipments such as train, aircraft weapon systems is spent much more during operation and maintenance phase than development phase. The maintenance cost for maintaining the availability and extending the life span of systems comprise a large proportion of systems operation cost. The cycle of preventive maintenance affects operation and maintenance cost a lot. In this study we introduce a way minimizing life-cycle cost of systems by calculating more reliable preventive maintenance period than the results of previous study using systems reliability data considered the reliability and failure effect ratio of sub-systems or components. We can solve the preventive maintenance period problem known as NP-Hard as quick as possible by using modified genetic algorithm than using other models introduced in previous study.

• 산업경영시스템학회지
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• 제40권1호
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• pp.165-172
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• 2017

Machines are physically or chemically degenerated by continuous usage. One of the results of this degeneration is the process mean shift. Under the process mean shift, production cost, failure cost and quality loss function cost are increasing continuously. Therefore a periodic preventive resetting the process is necessary. We suppose that the wear level is observable. In this case, process mean shift problem has similar characteristics to the maintenance policy model. In the previous studies, process mean shift problem has been studied in several fields such as 'Tool wear limit', 'Canning Process' and 'Quality Loss Function' separately or partially integrated form. This paper proposes an integrated cost model which involves production cost by the material, failure cost by the nonconforming items, quality loss function cost by the deviation between the quality characteristics from the target value and resetting the process cost. We expand this process mean shift problem a little more by dealing the process variance as a function, not a constant value. We suggested a multiplier function model to the process variance according to the analysis result with practical data. We adopted two-side specification to our model. The initial process mean is generally set somewhat above the lower specification. The objective function is total integrated costs per unit wear and independent variables are wear limit and initial setting process mean. The optimum is derived from numerical analysis because the integral form of the objective function is not possible. A numerical example is presented.

• 대한전기학회논문지:전력기술부문A
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• 제51권5호
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• pp.238-246
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• 2002

Utilities are trying to install the equipment of high quality to avoid deterioration of supply reliability. In addition, many sectionalizing switches which can decrease the total outage value for a fault are installed for the same reason. Therefore, utilities are interested in stun dards and criteria for installing switches to optimize the total cost on distribution systems. The affect of sectionalizing switches installed on distribution feeder is gradually decreased because the failure rate on distribution feeder is decreased. Also the automation for distribution systems is widely applied for the efficient operation. Therefore, the renewal for installation standards of sectionalizing switches Is required to reflect the current operation situation. The variable data is used to consider the KEPCO's real situation of distribution feeder as follows; the feeder capacity, connecting rate, feeder length, failure rate of distribution feeder, the failure rate of switches, perception time of feeder fault, the restoration time for a faulted section, the transfer time to other feeders, and the switching time. In this study, We propose equations which can determine the number of sectionalizing switches for minimizing the outage and switch installation cost.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2002년도 하계학술대회 논문집 A
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• pp.70-73
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• 2002

Utilities are trying to install the equipment of high quality to avoid deterioration of supply reliability. In addition, many sectionalizing switches which can decrease the total outage value for a fault are installed for the same reason. Therefore, utilities are interested in standards and criteria for installing switches to optimize the total cost on distribution systems. The affect of sectionalizing switches installed on distribution feeder is gradually decreased because the failure rate on distribution feeder is decreased. Also the automation for distribution systems is widely applied for the efficient operation. Therefore, the renewal for installation standards of sectionalizing switches is required to reflect the current operation situation. The variable data is used to consider the KEPCO's real situation of distribution feeder as follows; the feeder capacity, connecting rate, feeder length, failure rate of distribution feeder, the failure rate of switches, perception time of feeder fault, the restoration time for a faulted section, the transfer time to other feeders, and the switching time. In this study, We propose equations which can determine the number of sectionalizing switches for minimizing the outage and switch installation cost.

• 품질경영학회지
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• 제20권2호
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• pp.33-43
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• 1992

Items are assumed to fail by degradation. An appropriate stochastic model of such item is a cumulative process in which an item can fail only when the total amount of wear exceeds a prespecified failure level. This paper presents replacement policy in which an item is replaced at a certain level of wear before failure or at failure, whichever occurs first. Yet, when measuring the item wear level is very expensive, destructive or time-consuming, it may be economical to use substitutive characteristics that are correlated with the item wear level and relatively inexpensive to measure. The item's wear level could usually be estimated by monitoring such substitutive characteristics only except for a breakdown, which may be observed immediately at its occurrence. The purpose of this paper is to find an optimal periodic replacement policy based on such substitutive characteristics that balance the cost of replacement with the cost of failure and result in a minimum total long-run average cost per unit time. The optimal level of substitutive characteristics to replace the item is obtained. Numerical example illustrate how the model can be used to determine the optimal replacement policy.

• 한국신뢰성학회:학술대회논문집
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• 한국신뢰성학회 2004년도 정기학술대회
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• pp.183-190
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• 2004

Found important components in terms of frequency in the assembly (but not in terms of money). Component 39*** was most important. The failure mode was N69(no light on warning signal the cause of the failure was C15(bad connection). Formed a population for each component. Performed reliability and warranty cost analyses At the component level. At the subsystem level. At the system level. **They don'l trust the warranty cost analysis.** Reliability improvement. Among all the subsystems front \ulcorner subsystem is most vulnerable (among other things due to the large number of components in it), especially components 39*** and 28***.

• 대한산업공학회지
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• 제15권2호
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• pp.87-91
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• 1989

A warranty is a contractual obligation incurred by a producer in connection with the sale of a product. The warranty specifies that producer agrees to remedy certain failures in the product sold. There have been many articles dealing with warranties, but they have studied about optimal warranty cost for the warranty period. In this study, an optimal preventive maintenance time interval is computed. The optimal preventive maintenance time interval minimizing warranty cost for the warranty period is discussed. It is assumed that failure rate is increasing and the failure rate after preventive maintenance or corrective maintenance lies between good as new and bad as old.