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Tutorial for Discrete Rate Systems 333
A basic discrete rate model
• The packaging process yields 12 containers of yogurt per gallon of mix.
• Thecoolingcycleoccursona100footlongrefrigerationunit.Theyogurtmustbecooledfor at least 20 minutes before the containers can be packaged into cartons.
• Each carton holds 48 containers of yogurt
• There are two palletizing areas, one of which has a higher priority than the other.
• Pallets arrive every 2 minutes and can hold 24 cartons.
• Timeunitsareinminutesandthesimulationdurationis480minutes.
• TheblockscomefromtheRate,Item,andPlotterlibraries.
☞ The final Yogurt Production model, and the models that illustrate the steps described in this chapter, are located in the folder \Examples\Tutorials\Discrete Rate. To get the maximum ben- efit of this tutorial, it is recommended that you build the models yourself.
Starting a model and setting simulation parameters
The following steps are typical when starting any discrete rate model:
Open a new model worksheet
Give the command Run > Simulation Setup. In the Setup tab enter the simulation parame- ters:
End time: 480
Global time units: minutes
If they aren't already open, open the Rate, Item, Plotter, and Value libraries
Place an Executive block (Item library) on the top left corner of the model worksheet
As mentioned in the Introduction to this module, the Executive block does event scheduling and manages discrete rate and discrete event simulations. It must be present in every discrete rate and discrete event model.
Start small
In building any simulation model, it is easiest to start with a simplified subset of the process and add detail until you arrive at a completed representation of the system that's being modeled. This allows you to test at various stages while making the model building process more manageable.
The first step is to model a single line of production,
where one Tank holds product that moves to another
Tank at a constant rate. When you have finished this
portion of the tutorial, your model should look like the one shown above.
Basic yogurt production line
Discrete Rate

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