Bài giảng môn Quản trị kinh doanh - Chapter 8: Manufacturing planning and control

Manufacturing Planning and ControlMPC 6th EditionChapter 8Production Activity ControlProduction Activity Control (PAC) concerns the execution of material plans.A number of MPC activities, including Shop-floor Scheduling and Control (SFC), Vendor Scheduling and Follow-up, Order Release, and Purchasing fall partly or completely within the realm of Production Activity Control.AgendaProduction Activity Control in the MPC SystemResourceplanningSales and operationsplanningDemandmanagementMaster productionschedulingDetailed materialplanningMaterial andcapacity plansShop-floor scheduling and control (SFC)PurchasingDetailed capacityplanningVendor scheduling and follow-upOrder releaseProduction activity controlSystem Links–MPC and Production Activity ControlJust-in-Time (JIT) Effect on PACFormal systems for shop-floor control are largely unnecessary under JITPAC functions are simplifiedOrder release through kanbans or other pull systemLimited work-in-process inventoriesDetailed scheduling is not neededNo data collection or monitoring requirements–only raw material and finished goods inventoriesVendor scheduling may be more complex under JITProduction Activity Control and Company EnvironmentThe primary PAC objective is managing material flows to meet MPC plansOther objectives may pertain to efficient use of capacity, labor, tools, time, or materialsUnder JIT the objective is material velocityPAC objectives reflect the firm’s strategy and competitive positionProduction Activity Control TechniquesBasic Shop Floor ConceptsRouting and lead-time data are essential inputsRouting specifies the operation, its duration, and the work center performing the workLead times typically consist of four elementsRun timeSetup timeMove timeQueue timeOperation Setback ChartComponent partsSub-AssemblyFinished ProductPart D has three operationsLead-Time ManagementThe four elements of lead time (run, setup, move, and queue) can be compressed with good PAC managementA basic principle of MPC systems is to substitute information for inventoryThe knowledge of when an order will arrive at a work center replaces the need to WIP inventory feeding the work centerGantt ChartsGantt charts show a scheduleEach step listed separatelyRelationship between steps portrayed visuallyPriority Sequencing RulesDetermine which job to run next at a particular work centerWhen a job is near completion, the available jobs in the queue are evaluatedPriority Sequencing RulesCommon rulesOrder slack–work on the job with the least total slackSlack per operation–divide total slack by the number of remaining operations, then work on job with least slackCritical ratio–calculate (time remaining)/(work remaining) and work on job with lowest ratioShortest operation next–work on the job that can be completed most quicklyTheory of Constraints (TOC)TOC focuses effort on bottleneck resourcesBottlenecks limit the capacity of the entire plantObjective is to maximize throughputBottlenecks may be constraints other than work centersConstraints are identified, buffered with inventory, and their importance is stressed to the entire factoryTheory of Constraints SchedulingDrum-Buffer-RopeDrum–bottleneck work centers which control the tempo of workflow through the plantBuffer–inventory and/or scheduling activities to protect the throughput at bottlenecks from random variationRope–use of pull scheduling at non-bottleneck resourcesMaterial moves through non-bottleneck resources as quickly as possible, bottlenecks are managed for maximum efficiencyTOC SchedulingPotential bottlenecks are identified using rough-cut capacity planningScheduling is completed according to the work center typeCapacity Utilization ChartWork centers over a capacity threshold (80%) are considered bottlenecksBuffersTOC uses both safety stock and safety lead time at bottleneck operationsSafety lead time is introduced between sequential orders at the bottleneckSafety stock of completed parts from preceding, non-bottleneck operations is held in front of the bottleneck to prevent shortagesTOC and Lot SizingLot sizes are calculated differently for bottleneck and non-bottleneck resourcesFor the same finished item, lot sizes at different operations may be differentTOC splits orders at non-bottleneck resources and combines orders at bottlenecksThis maintains supply of non-bottleneck parts while reducing setup time and/or increasing efficiency at the bottleneckManaging the TOC ScheduleSchedule new orders on the bottleneck operations (drums)Finite backward schedulingExploiting the drumsIf necessary, add capacity to drums by moving work or outsourcingMaterial release–ropesRelease raw materials to non-bottlenecks only when scheduledProactive management of buffersEnsure that bottleneck resources are not starved for ordersElevating the drumIncrease capacity at the bottlenecks to allow the organization to growTOC ContributionsTOC Implementation IssuesRequires a major shift in manufacturing mindset (paradigm shift)Its OK to not work (at a non-bottleneck) if there are no ordersFirm needs sound systems, education, top-management support, and willingness to changeVendor Scheduling and Follow-UpObjective–align orders with due datesVendor must have continually updated information concerning prioritiesContractual agreements may limit the type and degree of change the vendor must accommodateUse of the Internet can enhance the speed and efficiency of information exchangePrinciplesProduction activity control system design must be in concert with the firm’s needs.Vendor capacities should be planned and scheduled with as much diligence as internal resources.Lead times must be managed.Feedback from the PAC should provide both status and early warning information to other MPC modulesPrinciplesE-based systems can improve communication between customer and vendor, reducing lead time and overhead.TOC scheduling provides improved performance by focusing on the constraining resources.TOC implementation requires a change in culture.Traditional priority rules can play a role in scheduling non-bottleneck resources.Stability in manufacturing loads and capacity plans facilitates shop-floor execution.Quiz – Chapter 8Production activity control (PAC) actions take place mainly in which section of the MPC system?The shop-floor control system is kept current on changes in material plans by the MRP system? (True/False)Formal shop-floor control systems are unnecessary under JIT? (True/False)A visual representation of the scheduling process can be provided by _________ charts.The TOC scheduling process is called ______-_________-_________.In TOC scheduling, buffers are maintained before and after _____________ resources.