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Simulation Based Production Planning, Scheduling, and Control. Johannes Krauth Sim-Serv. Overview. Planning Steps Methods Applied The Contribution of Simulation Examples The Future. Planning Steps. Production Programme Planning / Plant or Process Design (time horizon: years)
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Simulation Based Production Planning, Scheduling, and Control Johannes Krauth Sim-Serv
Overview • Planning Steps • Methods Applied • The Contribution of Simulation • Examples • The Future
Planning Steps • Production Programme Planning / Plant or Process Design (time horizon: years) • Production Planning (months / weeks) • Detailed Scheduling (days / hours) • Control
Overall Planning Objectives • Maximise Capacity Utilisation • Minimise Delays • Minimise Throughput Times • Minimise Work in Progress Note: Conflicting Objectives!!
Facility Planning • Based on assumed demand • Searches “optimal” match of needed and available capacity • Planning horizon: years • Not an ongoing activity
Optimal Match Needed per year: 10,400 h milling ______________ 8,500 h welding … Available per year: 4 machines = 5376 h (1 shift, 80% utilis.); = 10752 h (2 shifts) __________________ 4 workers = 8400 h 5 workers = 10080 h … ?
Limitations • no interdependencies taken into account • based on estimated / experienced degrees of capacity utilisation • adequate for strategic, long-term planning, when little information is available
Production Planning • Based on (expected) customer orders • Using fixed throughput times per step (based on experience or assumptions) • Accepts / rejects orders and fixes start and end dates
Limitations • Capacity assumed available • Actual shop floor status not taken into account • Waiting times included and therefore fixed • Applicable only when long delivery times are acceptable
Production Scheduling • Planning Horizon: 1 week – 1 day • Based on confirmed orders and actually available resources • Must take into account technical restrictions • Finds exact sequence of operations per work station
Production Scheduling • Must be “fit for reality”!
Contribution of Simulation • Detailed models • Exact representation of all processes, all needed resources • Realistic transition times, based on current shop floor status • All kinds of rules and constraints can be taken into account
Ways to Use Simulation: 1. Offline, from outside Simulation Model controls MRP /ERP System feeds back
Ways to Use Simulation 2. Online, as part of planning toolbox MRP / ERP System: Long Term Planning Module_____________________ Medium Term Planning Module___________________ Scheduling Module: Simulation Model Shop Floor
Contribution of Optimisation • Can use a large variety of criteria for “optimal” solutions • Finds very good schedules quickly • Takes away hours of routine work from the planners • Allows them to focus on the essentials
Examples • 2 Examples: Simulation helps optimise planning tool and process • 4 Examples: Simulation and Optimisation modules as part of planning toolbox
Conclusion from Examples: • Broad range of industry sectors • Leitstand / APS tools can complement existing MRP / ERP tools or run stand-alone • Typical benefits include • Higher capacity utilisation • Less WiP • Less delays, shorter throughput times • Payback often within a few months!!
Summary • Simulation Based Scheduling and Control offers substantial advantages • Many approaches available for different special requirements • Also useful for SMEs • Sim-Serv assists with selection of best suited approach