Machines and facilities are physically or chemically degenerated by continuous usage. One of the results of this degeneration is the process mean shift. The representative type of the degeneration is wear of tool or machine. According to the increasing wear level, non-conforming products cost and quality loss cost are increasing simultaneously. Therefore a periodic preventive resetting the process is necessary. The total cost consists of three items: adjustment cost (or replacement cost), non-conforming cost due to product out of upper or lower limit specification, and quality loss cost due to difference from the process target value and the product characteristic value among the conforming products. In this case, the problem of determining the adjustment period or wear limit that minimizes the total cost is called the ‘process mean shift’ problem. It is assumed that both specifications are set and the wear level can be observed directly . In this study, we propose a new model integrating the quality loss cost, process variance, and production volume, which has been conducted in different fields in previous studies. In particular, for the change in production volume according to the increasing in wear level, we propose a generalized production quantity function g(w). This function can be applied to most processes and we fitted the g(w) to the model. The objective equation of this model is the total cost per unit wear, and the determining variables are the wear limit and initial process setting position that minimize the objective equation.

1. 서 론
2. 기존 연구
3. 모형의 구성
    3.1 마모수준과 부적합률
    3.2 생산량 함수와 부적합품 비용
    3.3 생산량 함수와 품질손실비용
    3.3 생산량 함수를 고려한 최종모형
4. 결 론
References

• Do-Kyung Lee(금오공과대학교 산업공학부) | 이도경 Corresponding Author