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 by hijuney7

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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:            Available per year:
10,400 h milling            4 machines = 5376 h
                            (1 shift, 80% utilis.);
                            = 10752 h (2 shifts)
______________              __________________
8,500 h welding        ?    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
 Example: Assumed and Real Durations

Department     Estimated         Process
               Throughput Time   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
            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
              feeds
 System
              back
      Ways to Use Simulation
2. Online, as part of planning toolbox
               MRP / ERP System:
Long Term Planning Module_____________________
Medium Term Planning Module___________________
                                  Simulation Model
Scheduling Module:




                     Shop Floor
Typical “Leitstand” / APS tool
 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

								
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