Avoid jams with photo eyes

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In FlexSim, a photo eye is an object used to build logic into your simulation

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to avoid jams and ensure flow items are moving along a conveyor system as intended.

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Photo eyes are often included in real-world scenarios, such as conveyor systems in a fulfillment center.

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In the fulfillment center order consolidation simulation shown,

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it is possible for flow items to back up on the conveyor system as they wait to enter the racks.

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Use photo eyes to detect and help address potential jams.

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In this example, a photo eye appears on each conveyor in front of the pack wall.

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The green color of the line indicates the photo eye is clear.

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Stop the model and select a photo eye.

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In Properties, under Photo Eye, apply settings such as Block Time, Clear Time, and Offset Angle.

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Block Time sets the amount of time required for the photo eye to be considered blocked and turn red.

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It is important to set a block time that allows for the normal flow of items across the photo eye but will quickly detect any disruption in the flow.

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Here, the Block Time is set to “1” second.

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In the model, you can also select the photo eye to drag and place it at different points on the conveyor

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to test where it is best suited to detect potential jams.

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Additionally, you can adjust the position of the control point.

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If the photo eye is blocked and turns red, it does not perform a mitigating action.

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In this case, the control point is connected to the photo eye

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and contains the logic that helps determine the path of the flow item based on the state of the photo eye.

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Select the control point and right-click.

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In Properties, under Triggers, click the Custom Code for On Arrival.

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First, the code is set to check the item’s StationNum label to see if it matches the Station;

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if so, it will route the item to that Station.

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In the Control Point Properties, enable Show Connections.

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A connection exists between the control point and photo eye.

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The code shown here references the photo eye as the new destination for the item.

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The code then checks the state of the photo eye to return the state value.

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Right now, the state is clear.

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However, if the photo eye turns red, indicating a jam, then the state changes to blocked.

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If the state is not blocked, then the control point will direct the item to the photo eye,

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so it can continue to the exit transfer and then to the rack.

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If the state is blocked, then the control point directs the item to stay on the conveyor and loop back around

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until the photo eye is in an unblocked state.

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Setting up the photo eye and control points in this way helps to regulate the flow of items on your conveyor system.

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Now you can include photo eyes when you build a simulation of order consolidation in a fulfillment center.