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In conveyor systems, sorting (sortation) is needed when high quantities of items need to be transported to different destinations based on varying criteria. Sorters can divert items from incoming conveyor lines to shipping lanes, palletizing operations, packing stations, or other sorting stations.

To sort items on a conveyor in FlexSim, you'll need to use a Decision Point or Photo Eye with the Send Item Behavior to sort items to various destinations. The Send Item Behavior uses two fields to determine how it should sort items:

• The Condition field - This field decides "Should I divert this item?" and sorts items based on particular conditions. (See The Condition field for more information.)
• The Destinations field - This field decides "Which destination should I send the item to?" and sorts items to multiple possible destinations based on criteria you define.

You can use a combination of different settings in these two fields to build complex sorting logic into your conveyors. In the following sections, we'll demonstrate two different methods for sorting these items, each one focusing on sorting using a different field.

Sorting Using the Condition Field

To sort items using the Condition field, we will add a Decision Point to the main line conveyor and connect it to a single Decision Point on the diverting conveyor. Then we will add the Send Item Behavior on the OnArrival Trigger to the Decision Point on the main line. The Condition field on the Send Item Behavior will be set to randomly sort 30% of items to the diverting conveyor, as shown in the following image:

To create this kind of sortation system:

1. Add the conveyors and add any additional Fixed Resources such as Sources and Sinks. (See Adding Conveyors to a Simulation Model.)
2. Connect the conveyors together and connect to the conveyors to the Fixed Resources. (See Connecting Conveyors.)
3. Place a Decision Point at the first junction on the conveyor where items could be diverted to different conveyor lines.
4. Place a Decision Point at the beginning of the conveyor line where 30% of the products will be diverted.
5. Make an input/output port connection ('A' connect) from the sending Decision Point to the receiving Decision Point.
6. Double-click the sending Decision Point to open its Properties dialog box.
7. In the Decision Point tab, click the Plus sign next to the OnArrival Trigger and select Send Item from the menu. (See Send Item for more in-depth information about this Behavior.)
8. A dialog box will pop up. In the Condition field, enter in the following expression: bernoulli(30, 1,0). This bernoulli distribution will randomly return a value of 1 (true) 30 percent of the time, and 0 (false) 70 percent of the time.

1. From the Destination menu, enter outobject(current,1). This means when the condition is true (30% of the time), the item will be sent to the Decision Point connected to the first output port of the main line Decision Point, i.e. the divert conveyor's Decision Point.
2. Click OK to apply the settings and close the Properties dialog box.
3. To test the simulation, click Reset and Run on the simulation control bar. As the simulation runs, the items should sort to the appropriate conveyor lines.

Sorting Using the Destination Field

To sort items using the Destination field, will will add a single Decision Point to the main line conveyor and connect it to multiple Decision Points on diverting conveyors. Then we will add the Send Item Behavior on the OnArrival Trigger to the Decision Point on the main line. The Destination field on the Send Item Behavior will determine which lanes the items will be diverted to based on their item type. In this example, items with an itemtype 1 (the red boxes) are diverted to the first conveyor line. Items with an itemtype 2 (the green boxes) are diverted to the second conveyor line, etc., as shown in the image below:

To create this kind of sortation system:

1. Add the conveyors and add any additional Fixed Resources such as Sources and Sinks. (See Adding Conveyors to a Simulation Model.)
2. Connect the conveyors together and connect to the conveyors to the Fixed Resources. (See Connecting Conveyors.)
3. In the Source'sTriggers tab, add an OnCreation Trigger to Set Itemtype and Color. Define the Item Type as duniform(1, 5).The Source will randomly create items with a range of itemtypes between 1 and 5. Each itemtype correlates to a specific color.

1. Place a Decision Point at the first junction on the conveyor where items could be diverted to different conveyor lines.
2. Place Decision Points at the beginning of each conveyor line to act as a reference point for the first Decision Point. Notice that in this example, there isn't a Decision Point on the fifth conveyor line. If an item doesn't get diverted to the first four conveyors, it will end in the fifth conveyor line.
3. Make an input/output port connection ('A' connect) from the first Decision Point to each of the other Decision Points.
4. In this example, the order in which you connect the Decision Points matters because the rank of the output port connection will determine where the item is routed. Items with an itemtype 1 will be routed to the Output Port 1, etc. To view or change Output Port rankings, double-click the first Decision Point to open the Properties dialog box. Then click the General tab and select Output Ports from the Ports menu. Re-rank the Output Ports if necessary. (If you need to know the name of each Decision Point, its Properties dialog box displays its name in the top. By default, they are named DP1, DP2, etc. based on the order in which they were added to the model.)
5. Now you will need to add the Send Item behavior to the first Decision Point. With the Properties dialog box still open, click the Decision Point Type tab. Click the Plus sign next to the OnArrival Trigger. Select Send Item from the list of Behaviors. (See Send Item for more in-depth information about this Behavior.)
6. A Behavior Settings dialog box will pop up. In the Condition menu, select Always and the menu will then display the word true. This means that any item arriving at the Decision Point will always be sent.
7. In the Destination menu, select Output Port by Item Type and the menu will then display the expression outobject(current,getitemtype(item)). This means that it will send the item to a port based on its item type. Items with itemtype 1 will be sent to the first Output Port, etc.
8. Click OK to apply the settings and close the Properties dialog box.
9. To test the simulation, click Reset and Run on the simulation control bar. As the simulation runs, the items should sort to the appropriate conveyor lines.

Sending to Downstream Fixed Resources

When sending items to multiple downstream fixed resources, you connect the Decision Point on the conveyor to Exit Transfers instead of other decision points. Items sent to an exit transfer will go to the object connected to that exit transfer.

The image below shows the result of the decision point sending items with itemtype 1 to the exit transfer connected to Queue8 while any other items are sent to Queue7.

You can use these basic methods to do other kinds of complex sorting. You can familiarize yourself with the available Behaviors by reading the chapter on Photo Eye and Decision Point Behaviors, especially the section on the Send Item Behavior.