2 Learning ObjectivesExplain what scheduling involves and the importance of good scheduling.Discuss scheduling needs in high-volume and intermediate-volume systems.Discuss scheduling needs in job shops. Use and interpret Gantt charts, and use the assignment method for loading.Discuss and give examples of commonly used priority rules.Describe some of the unique problems encountered in service systems, and describe some of the approaches used for scheduling service systems.
3 Last stage of planning before production occurs SchedulingSpecifies when labor, equipment, facilities are needed to produce a product or provide a serviceLast stage of planning before production occurs
4 Batch Production Process Industry Mass Production Project Scheduled OperationsProcess IndustryLinear programmingEOQ with non-instantaneous replenishmentMass ProductionAssembly line balancingProjectProject -scheduling techniques (PERT, CPM)Batch ProductionAggregate planningMaster schedulingMaterial requirements planning (MRP)Capacity requirements planning (CRP)
5 Objectives in Scheduling Meet customer due datesMinimize job latenessMinimize response timeMinimize completion timeMinimize time in the systemMinimize overtimeMaximize machine or labor utilizationMinimize idle timeMinimize work-in-process inventoryThere is no single scheduling rule that optimizes all of these performance criteria. We consider the trade-offs.
6 Scheduling Low-Volume Systems Loading - assignment of jobs to process centersSequencing - determining the order in which jobs will be processedJob-shop schedulingScheduling for low-volume systems with many variations in requirements
7 Assignment of jobs to process centers LoadingAssignment of jobs to process centersPerform work with most efficient resourcesUse assignment method of linear programming to determine allocation
8 LoadingInfinite loading – jobs are assigned to work centers without regard for the capacity of the work center.Finite loading – jobs are assigned to work centers taking into account the work center capacity and job processing timesVertical loading / Horizontal loadingForward scheduling – scheduling ahead from some point in time.Backward scheduling – scheduling by working backwards in time from the due date(s).Schedule chart – a form of Gantt chart that shows the orders or jobs in progress and whether they are on schedule.
9 SequencingSequencing: Determine the order in which jobs at a work center will be processed.Workstation: An area where one person works, usually with special equipment, on a specialized job.Priority rules: Simple heuristics used to select the order in which jobs will be processed.Job time: Time needed for setup and processing of a job.
10 If no order specified use first-come first-served (FCFS) Priority RulesFCFS - first come, first servedSPT - shortest processing timeEDD - earliest due dateCR - critical ratioS/O - slack per operationRush - emergencyIf no order specified use first-come first-served (FCFS)
11 Performance Measures of Priorities Meeting due dates of customers or downstream operations.Minimizing the flow time (the time a job spends in the process).Minimizing work-in-process inventory.Minimizing idle time of machines or workers.9
12 Assumptions of Priority Rules The setup of jobs is knownSetup time is independent pf processing sequenceSetup time is deterministicThere will be no interruptions in processing such as:Machine breakdownsAccidentsWorker illness
13 Two Work Center Sequencing Johnson’s Rule: technique for minimizing completion time for a group of jobs to be processed on two machines or at two work centers.Minimizes total idle timeSeveral conditions must be satisfied
14 Johnson’s Rule Conditions Job time must be known and constantJob times must be independent of sequenceJobs must follow same two-step sequenceJob priorities cannot be usedAll units must be completed at the first work center before moving to second
15 Johnson’s Rule Optimum Sequence List the jobs and their times at each work centerSelect the job with the shortest timeEliminate the job from further considerationRepeat steps 2 and 3 until all jobs have been scheduled
16 Sequencing Jobs Through Two Serial Process Johnson’s RuleList time required to process each job at each machine. Set up a one-dimensional matrix to represent desired sequence with # of slots equal to # of jobs.Select smallest processing time at either machine. If that time is on machine 1, put the job as near to beginning of sequence as possible.If smallest time occurs on machine 2, put the job as near to the end of the sequence as possible.Remove job from list.Repeat steps 2-4 until all slots in matrix are filled and all jobs are sequenced.
17 Work package Gantt Chart Input/Output Control MonitoringWork packageShop paperwork that travels with a jobGantt ChartShows both planned and completed activities against a time scaleInput/Output ControlMonitors the input and output from each work center
18 Scheduling Difficulties Variability inSetup timesProcessing timesInterruptionsChanges in the set of jobsNo method for identifying optimal scheduleScheduling is not an exact scienceOngoing task for a manager
19 Minimizing Scheduling Difficulties Set realistic due datesFocus on bottleneck operationsConsider lot splitting of large jobs
20 Scheduling Services Considerations Scheduling services different from manufacturingInability to store or inventory servicesRandom nature of customer requests for servicePoint of customer contactBack-office operationsFront-office operations
21 Controls customer arrivals for service Reservation systems Scheduling ServicesAppointment systemsControls customer arrivals for serviceReservation systemsEstimates demand for serviceScheduling the workforceManages capacity for serviceScheduling multiple resourcesCoordinates use of more than one resource
22 The goal is to maximize the revenue generated by the fixed capacity Yield ManagementYield Management – the application of pricing strategies to allocate capacity among various categories of demand.The goal is to maximize the revenue generated by the fixed capacityFixed capacityHotel, motel roomsAirline seatsUnsold rooms or seats cannot be carried over
23 Hospitals, police/fire departments, restaurants, supermarkets Cyclical SchedulingHospitals, police/fire departments, restaurants, supermarketsRotating schedulesSet a scheduling horizonIdentify the work patternDevelop a basic employee scheduleAssign employees to the schedule
24 Labor is very flexible resource Employee SchedulingBecause:Labor is very flexible resourceScheduling workforce is complicated, repetitive taskHeuristics are commonly usedThere is a lot if industry specific software available.
25 Service Operation Problems Cannot store or inventory servicesCustomer service requests are randomScheduling service involvesCustomersWorkforceEquipment