Create a subset calculation and calculation constraints within a zone

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In FlexSim, creating subsets allows you to control flow items and gather valuable statistics for Zones within your process flow.

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Additionally, you can apply calculations to a subset, and then set up calculation constraints to further control the activity of those items.

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In this example, a simple process flow and a Dashboard are already set up.

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Tokens enter the flow, receive a random weight label of between 5 and 15 pounds, and then flow into the Zone based on specific constraints.

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The Zone also has a Heavy Parts subset that was created to identify items that are greater than or equal to 10 pounds.

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To add a subset calculation to the Zone, first, create a new subset.

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With Zone selected in the flow, in Properties, click More Properties.

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In the Zone Properties dialog, you see the Heavy Parts subset.

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Add a new Subset called “All tokens” and then reorder the subsets, so that the new one appears first.

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This subset includes every token that enters the Zone.

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Now, Add a Subset Calculation.

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In the Calculation name column, enter “Total Weight”, and in the Label/expression to sum field, type “Weight”.

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This creates a subset of all tokens that uses the weight labels to calculate the combined weight of tokens in the zone.

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Click Apply, and then OK.

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Reset, Run, and Step the model forward.

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Then, stop the model, and with Zone selected, in Properties, click View Status.

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On the Subsets tab, you see the data for both subsets.

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For the All Tokens subset, the Content row shows the Current, Average and Maximum number of tokens in the Zone.

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The Total Weight row shows the Current total weight of tokens in the Zone,

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as well as the average and maximum total weights for tokens that have been in the Zone.

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Next, on the Dashboard, add a Zone Statistics > Table.

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In Properties, select the Zone sampler, and then select the Zone in the process flow.

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In the Statistic drop-down, there are multiple Calculation statistics that you can select from.

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In this case, select Calculation Total.

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Then, deselect Minimum.

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It is also important to remember to manually select the Subset/Calculation field.

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If you use the default selection, as shown, when you Reset and Run the model, the chart will not populate properly.

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Here, select All Tokens Total Weight for the Subset/Calculation.

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Then, Reset the model and the error number disappears from the table.

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Now, Run the model forward, and then Stop it to see the Current, Maximum, and Average weights of tokens in the Zone.

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Continue running the simulation to view more statistics, and then Stop and Reset the model.

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Next, in Properties, expand Statistic again, and notice that you can also show a Calculation Input,

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the total weight of all tokens that enter the Zone throughout the simulation,

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or a Calculation Output, which shows the same for all tokens that exit the Zone.

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In this case, select Calculation Per Token.

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Now, when you Run the model, this calculation looks at an individual token in the Zone at a given time.

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You can use calculations with any type of label.

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For example, you can apply a cost label to items in your flow, and then calculate a total cost of all items.

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Next, apply a constraint to the calculation.

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With Zone selected, in Properties, select More Properties.

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In the Zone Properties dialog, click the Subset Constraints tab.

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Right now, there is a constraint applied to limit the number of heavy tokens in the Zone to 2.

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Delete this, and then create a new constraint to all tokens by clicking Add > Add constraint to: All Tokens.

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Expand Calculation and select Total Weight.

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Then, set the Value to “100” pounds.

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This means only 100 total pounds can be in the Zone at a given time.

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Click Apply, and then OK.

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Run, and Step the model forward until you meet the limit.

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Here, there are two tokens waiting to enter the Zone because the weight restriction has been met.

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Select the Zone, and in Properties, click View Status.

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In the Zone Status dialog, 92.28% of the limit has been reached.

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If you select the waiting tokens in the flow, you see in Properties, that their Weight would exceed the 100-pound limit.

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Therefore, the tokens wait to enter the Zone.

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Next, on the Dashboard, add a Zone Statistics > Line Chart, and then sample the Zone.

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Expand the Statistic drop-down one more time to look at the request options.

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Calculation Request Total provides the total weight of parts requesting to enter the Zone.

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Calculation Request Input and Output gather the total weights of tokens that request to enter the Zone,

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and that have entered the Zone, respectively.

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In this case, select Calculation Request Total.

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Select All Tokens: Total Weight for the Subset/Calculation, and then Run the simulation.

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The chart displays the total weight of tokens waiting to enter the Zone at a given time.

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For example, Stop the simulation to see that, shortly after 8:01 AM, just over thirty pounds of weight was waiting to enter the Zone.