Bài giảng Operations Management - Supplement 14: Maintenance

MaintenanceMcGraw-Hill/Irwin Copyright © 2012 by The McGraw-Hill Companies, Inc. All rights reserved.You should be able to:Explain the importance of maintenance in production systemsDescribe the range of maintenance activitiesDiscuss preventive maintenance and the key issues associated with itExplain breakdown maintenance and name the key issues associated with itState how the Pareto phenomenon pertains to maintenance decisions14S-*Student SlidesMaintenanceAll activities that maintain facilities and equipment in good working order so that a system can perform as intendedMaintenance activity categories:Buildings and groundsEquipment maintenance14S-*Student SlidesThe goal of maintenance is to keep the production system in good working order at minimal costReasons for wanting to keep equipment and machines in good operating condition:Avoid production or service disruptionsNot add to production or service costsMaintain high qualityAvoid missed delivery dates14S-*Student SlidesReactive:Breakdown maintenanceDealing with breakdowns or problems when they occurProactive:Preventive maintenanceReducing breakdowns through a program of lubrication, adjustment, cleaning, inspection, and replacement of worn parts14S-*Student SlidesThe goal of preventive maintenance is to reduce the incidence of breakdown or failures in the plant or equipment to avoid the associated costsLoss of outputIdle workersSchedule disruptionInjuriesDamage to other equipment, products, or facilitiesRepairsInventories of spare partsRepair tools and equipmentRepair specialists14S-*Student SlidesIt is periodicIt can be scheduled according to the availability of maintenance personnel and to avoid interference with operating schedulesMaintenance is scheduled using some combination ofThe result of planned inspections that reveal a need for maintenanceAccording to the calendar (passage of time)After a predetermined number of operating hours14S-*Student SlidesThe goal is to strike a balance between the cost of preventive maintenance and the cost of breakdownThe amount of preventive maintenance, therefore, is a function of the expected frequency of breakdown, the cost of breakdown, and the cost of preventive maintenanceStudent Slides14S-*The frequency of breakdown of a machine per month is $1,000 and the cost of preventive maintenance is $1,250 per month. If preventive maintenance is performed, the probability of a machine breakdown is negligible. Should the manager use preventive maintenance, or would it be cheaper to repair the machine when it breaks down?Number of breakdowns0123Frequency of occurrences.20.30.40.10Student Slides14S-*Number of breakdowns0123Frequency of occurrences.20.30.40.1014S-*Student SlidesSuppose the average time before breakdown is normally distributed with a mean of 3 weeks and a standard deviation of .60 weeks. If breakdown cost average $1,000 and preventive maintenance costs $250, what is the optimal maintenance interval?Find the number of standard deviations from the mean represented by an area under the normal curve of .25Using the standard normal table, it is -0.67Use this value to determine the maintenance interval14S-*Student SlidesPredictive maintenanceAn attempt to determine when best to perform preventive maintenance activitiesIdeally, preventive maintenance will be performed just prior to a breakdown or failure because this will result in the longest possible use of facilities or equipment without a breakdown Total productive maintenanceJIT approach where workers perform preventive maintenance on the machines they operate14S-*Student SlidesMaintenance problems are sometimes designed into products:Poor designDesigner have accorded other aspects of design greater importanceCostAppearance is more important than maintenance activitiesStudent Slides14S-*Approaches to dealing with breakdowns:Use of standby or backup equipmentInventories of spare parts are maintainedUse operators who are able to perform at least minor repairs on the equipment they operateHave repair people who are well trained and readily available to diagnose and correct problems14S-*Student SlidesWhen breakdowns become frequent and/or costly:What is the cost of replacement compared to continued maintenance?Issues:Predicting breakdownsTechnological changeSystem disruptionsTraining employees on the use of new equipmentForecast of future demand14S-*Student Slides