Simulation Model Development Methodology

The methodology used for simulation model building generally follows a four phase process. Each simulation project may have different goals in the overall scope of work, but Base Simulation model development is usually derived from the four phase process methodology. This process will ensure an accurate simulation model is created.

Phase 1 - Pre Model Activity

• Kick off meeting
• Definition of system goals
• Simulation scope of work
• List of clarifications and assumptions
• Develop functional specification
• Create data simulation to prove overall concept

The kickoff meeting is used to detail the goals that the simulation will accomplish. The Simulation Consultant, Systems Engineers, and Project Managers usually attend this meeting. The system is reviewed in detail and a scope of work is determined for the simulation effort.

A functional specification is then developed to outline goals of the simulation and to define modeling parameters. A description of operations, modeling assumptions, data requirements and definition are the core of the functional specification. A list of simulation deliverables is also included in the specification. The participants mentioned above approve the document to establish a common understanding for all involved in the project.

If appropriate, a data model is created. The data model will test volumes and processes. This is the first step in detecting operational or process difficulties. The data model is also a useful verification tool for the overall simulation model to test against.

Phase 2 - Base Simulation Model Development

• Convert AutoCAD drawings to an AutoMod format

• Input Graphics into AutoMod
       A. Define and draw conveyor path
       B. Create resources
       C. Create product appearance
       D. Input labels
       E. Input robots – OPTIONAL
       F. Define operators and walk paths – OPTIONAL

• Programming of AutoMod Simulation
       A. AutoMod creation process
       B. Read product arrival profiles
       C. Function of resources and their processing rates
       D. Emulate "Sequence of Operations"
       E. Develop system scheduling (arrival & dispatch profile, personnel scheduling)

• Simulation Model Validation
       A. Examine system throughput
       B. Validate system with system design engineers
       C. Uncover and expose possible errors in the simulation model

• Incorporate any changes required

The most challenging and time consuming process of simulation model creation is the actual programming. This is the point where all data and assumptions are applied to the system layout to determine validity of the design. If changes are required after a review of the simulation model inputs, they are implemented and Phase 3 begins.

Phase 3 - Simulation Model Analysis

• Conduct simulation model runs

• Examine throughput values
       A. Interpret data
       B. Verify output

• Collect data produced by model run
       A. Create spreadsheets and graphs
       B. Pinpoint system bottlenecks or starvation

• Create Simulation Report

This is the phase of the overall simulation procedure where the model is ready to be run. The model can simulate running the product through the system over a period of days. The period of time that the model simulates is a variable and depends on such items as production schedules, shift schedules, product mix, and varying system downtimes. After the model has been run the throughput is examined, the data collected and reports are generated. The Base Model Report will explain the simulation model results and include sections for conclusions and recommendations.

Phase #4 - Experimentation

• Define experimentation goals

• Incorporate changes to simulation model
A. Layout changes
B. Process changes

• Validation and verification

• Experimental simulation model runs

• Document data

• Update Final Report

After reviewing the results of the base simulation model and presenting the simulation to the customer, there are often “What If” scenarios to be considered. The experimentation phase takes these scenarios and incorporates them into the simulation model. This allows the customer, systems engineers, and the simulation consultant to adjust the system simulation to accommodate these other considerations.

In this phase an Excel based Graphical User Interface (GUI) should be developed to allow easy model input data and system parameter manipulation. This means the model can be quickly changed and run again to view the models output results.

Simulation modeling is a very important tool in delivering a total system that will meet the needs of the customer on the day of start up and well into the future.