All machines deteriorate in performance over time. The phenomenon that causes such performance degradation is called deterioration. Due to the deterioration, the process mean of the machine shifts, process variance increases due to the expansion of separate interval, and the failure rate of the machine increases. The maintenance model is a matter of determining the timing of preventive maintenance that minimizes the total cost per wear between the relation to the increasing production cost and the decreasing maintenance cost. The essential requirement of this model is that the preventive maintenance cost is less than the failure maintenance cost. In the process mean shift model, determining the resetting timing due to increasing production costs is the same as the maintenance model. In determining the timing of machine adjustments, there are two differences between the models. First, the process mean shift model excludes failure from the model. This model is limited to the period during the operation of the machine. Second, in the maintenance model, the production cost is set as a general function of the operating time. But in the process mean shift model, the production cost is set as a probability functions associated with the product. In the production system, the maintenance cost of the equipment and the production cost due to the non-confirming items and the quality loss cost are always occurring simultaneously. So it is reasonable that the failure and process mean shift should be dealt with at the same time in determining the maintenance time. This study proposes a model that integrates both of them. In order to reflect the actual production system more accurately, this integrated model includes the items of process variance function and the loss function according to wear level.

1. 서 론
    1.1 설비보전모형
    1.2 공정평균이동
2. 기존 연구
3. 모형의 구성
    3.1 품질특성치 Xω
    3.2 마모수준 ω와 부적합률 P(ω)
    3.3 설비의 보전(재설정 및 교환) 비용
    3.4 공정평균 이동에 의한 부적합 비용
    3.5 적합품에 대한 품질손실비용
    3.6 고장과 평균이동을 고려한 최종 모형
4. 예제 및 결론
References

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