Bài giảng Operations Management - Supplement 14 Maintenance

MaintenanceSupplement 14Copyright © 2015 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education.Supplement 14: Learning ObjectivesYou should be able to:LO 14S.1 Explain the importance of maintenance in production systemsLO 14S.2 Describe the range of maintenance activitiesLO 14S.3 Discuss preventive maintenance and the key issues associated with itLO 14S.4 Explain breakdown maintenance and name the key issues associated with itLO 14S.5 State how the Pareto phenomenon pertains to maintenance decisionsThe 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 datesMaintenance GoalsLO 14S.1Operations capacity is reduced, and orders are delayedThere is no output, but overhead continues, increasing the cost per unitThere are quality issuesOutput may be damagedThere are safety issuesEmployees or customers may be injuredBreakdown ConsequencesLO 14S.1Reactive:Breakdown maintenanceDealing with breakdowns or problems when they occurProactive:Preventive maintenanceReducing breakdowns through a program of lubrication, adjustment, cleaning, inspection, and replacement of worn partsMaintenance OptionsLO 14S.2The 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 specialistsPreventive MaintenanceLO 14S.3It 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 hoursPreventive Maintenance ScheduleLO 14S.3Preventive Maintenance: FrequencyThe 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 maintenanceLO 14S.3Frequency: Example 1The 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.20.30.40.10LO 14S.3Frequency: Example 1Number of breakdowns0123Frequency of occurrences.20.30.40.10LO 14S.3Suppose the average time before breakdown is normally distributed with a mean of 3 weeks and a standard deviation of .60 weeks. If breakdown cost averages $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 intervalFrequency: Example 2LO 14S.3Predictive 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 operateMaintenance ApproachesLO 14S.3Approaches 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 problemsBreakdown ProgramsLO 14S.4When 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 demandReplacementLO 14S.4Breakdown programs are most effective when they take into account the degree of importance of a piece of equipment has in the operations system, and the ability of the system to do without it for a period of time.The Pareto phenomenon exists in such situations:Few pieces of equipment will be extremely important to the functioning of the systemThese justify considerable effort and/or expenseSome will require moderate effort and/or expenseMany will justify minimal effort and/or expensePareto Phenomenon & MaintenanceLO 14S.5