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``````342 Tutorial for Discrete Rate Systems
A basic discrete rate model
In the popup for the second unit setting (to: containers), select New Unit and name the new flow unit cartons.
So that each carton will hold 48 containers, enter Conversion factor: 48 containers/car- tons.
If you check the box for Show unit change on icon, the area above the icon will display the text containers=>cartons.
Label the new block Change Unit 2.
If you clone the plot pane onto the model worksheet, your model should be similar to the fol-
lowing:
Packaging containers into cartons
Although the amounts will vary depending on the yogurt process’s constraint rate and the potential unavailability of fruit due to maintenance, when you run the model it should result in approximately 8,000 cartons. (Each carton holds 48 containers and the process should have produced about 390,000 containers of yogurt.)
The model’s assumptions state that there is a palletizing area where cartons are stored for ship- ment. One empty pallet arrives every 2 minutes and each pallet can hold 24 cartons. If there is no empty pallet to replace it, the flow of yogurt stops when a full pallet leaves. As discussed below, this is easily represented using the Rate library’s Interchange block and discrete event blocks from the Item library.
Interchange block
The Interchange block represents a tank, or holding area, where the flow of discrete rate blocks can interact with items from discrete event blocks. The block can only get one item at a time. In its default behavior (Tank only exists while item is in it), the block behaves similar to an on/off switch. When it has an item, it has a capacity for flow; in the absence of an item, the block has no flow capacity. (In the block’s alternate behavior, the tank has capacity and items that come to it can contribute flow to the block and/or remove flow from it.)
In this model, empty item/pallets are generated randomly. The arrival of an item/pallet causes the Interchange block to have flow capacity; the maximum capacity of 24 cartons is entered in
Discrete Rate

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