Post on 05-Apr-2018
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Simulation Based Production
Planning, Scheduling, andControl
Johannes Krauth
Sim-Serv
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Overview
Planning Steps
Methods Applied
The Contribution of SimulationExamples
The Future
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Planning Steps
Production Programme Planning /
Plant or Process Design
(time horizon: years)Production Planning (months / weeks)
Detailed Scheduling (days / hours)
Control
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Overall Planning Objectives
Maximise Capacity Utilisation
Minimise DelaysMinimise Throughput Times
Minimise Work in Progress
Note: Conflicting Objectives!!
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Facility Planning
Based on assumed demand
Searches optimal match of needed
and available capacityPlanning horizon: years
Not an ongoing activity
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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 h5 workers = 10080 h
?
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Limitations
no interdependencies taken intoaccount
based on estimated / experienceddegrees of capacity utilisation
adequate for strategic, long-termplanning, when little information isavailable
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Production Planning
Based on (expected) customer orders
Using fixed throughput times per step
(based on experience or assumptions)Accepts / rejects orders and fixes startand end dates
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Example: Assumed and Real Durations
Department Estimated
Throughput Time
Process
Time
Lathing 20 days 1 hour
Machining 5 days 20 hours
Surface Treatm. 7 days 1.5 hours
Polishing 7 days 10 hours
Assembly 15 days 20 hours
Total 54 days 52.5 hours
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Limitations
Capacity assumed available
Actual shop floor status not taken into
accountWaiting times included and thereforefixed
Applicable only when long deliverytimes are acceptable
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Production Scheduling
Planning Horizon: 1 week 1 day
Based on confirmed orders and
actually available resourcesMust take into account technicalrestrictions
Finds exact sequence of operations perwork station
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Production Scheduling
Must be fit for reality!
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Contribution of Simulation
Detailed models
Exact representation of all processes,
all needed resourcesRealistic transition times, based oncurrent shop floor status
All kinds of rules and constraints canbe taken into account
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Ways to Use Simulation:
MRP /ERP
System
Simulation Modelcontrols
feeds
back
1. Offline, from outside
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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
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Typical Leitstand / APS tool
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Contribution of Optimisation
Can use a large variety of criteria foroptimal solutions
Finds very good schedules quicklyTakes away hours of routine work fromthe planners
Allows them to focus on the essentials
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Examples
2 Examples: Simulation helps optimise
planning tool and process4 Examples: Simulation andOptimisation modules as part ofplanning toolbox
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Conclusion from Examples:
Broad range of industry sectors
Leitstand / APS tools can complementexisting 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!!
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Summary
Simulation Based Scheduling andControl offers substantial advantages
Many approaches available for differentspecial requirements
Also useful for SMEs
Sim-Serv assists with selection of bestsuited approach