Shuffling Logic on Double Deep rack storage in ASRS system

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Thanaporn asked Feb 20, '25 Felix Möhlmann commented Mar 6, '25

Shuffling Logic on Double Deep rack storage in ASRS system

Dear All,

I would like to create a model for a Double Deep storage ASRS system, and I need to implement a Shuffling Logic on the Rack.

The logic is if the ASRS needs to retrieve a pallet from inside the rack but there is another pallet blocking it in the front, the blocking pallet must first be moved to an empty rack location. Then, the ASRS can retrieve the inner pallet. After that, the ASRS should bring the moved pallet returned to its original position inside the rack. I have attached a sample model below.

Please provide your suggestions and guidance.

Thank you for your help and answer.

Rack Shuffling Logic Example.fsm

Software Version:

FlexSim 24.2.2

rack asrs

1740044812063.png (1022.0 KiB)

rack-shuffling-logic-example.fsm (44.3 KiB)

5 |100000

Attachments: Up to 12 attachments (including images) can be used with a maximum of 23.8 MiB each and 47.7 MiB total.

Answer 1 · 2025-02-20T12:29:32Z

Felix Möhlmann answered Feb 20, '25 Felix Möhlmann commented Mar 6, '25

You can use the pickRank property of the Slot.Item class to determine if the item can be moved right away or other items need to be moved out of the way first. If that is the case, you can query those items and move them to a different slot.

There are some complications when using port-connections and a minimum dwell time for the material flow. If an item is shuffled to another slot, either this happens before the dwell time has elapsed, causing an error when it does. Or there is already a task sequence to move that item present. In this case moving it to a different slot will start another dwell time counter and eventually create a second task sequence for the same item.

That could be solved by checking if a task sequence to move the blocking item already exists and simply prioritize that one over the item behind it. In the attached example model I opted to just pull items from a list one by one though.

rack-shuffling-logic-example_1.fsm

rack-shuffling-logic-example-1.fsm (56.5 KiB)

· 3

5 |100000

Attachments: Up to 12 attachments (including images) can be used with a maximum of 23.8 MiB each and 47.7 MiB total.

Thanaporn commented · Feb 27 at 11:57 AM

Thank you so much for your support.

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Thanaporn commented · Mar 05 at 02:01 PM

Double dept ASRS storage.fsm

Dear Felix,

Please find my model attached.

Could you please suggest a solution?
I have 1,274 SKUs and want my model to start with 90% rack capacity, ensuring the same SKU is always stored in the same bay. When a new pallet arrives, ASRS must follow the same rule. I tried using Find Slot and Move Object, but it didn’t work.

Could you please suggest me?.

Thank you for your help!

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double-dept-asrs-storage.fsm (4.8 MiB)

Felix Möhlmann Thanaporn commented · Mar 06 at 12:44 PM

The "simple" way would be to have fixed slots per SKU. In the attached model I wrote a script that paints the SKUs to the slots in a somewhat sensible manner. So every time an item needs a slot, you match the SKU of the item with the slot.

double-dept-asrs-storage_1.fsm

In theory you could try to have variable slots assigned to SKUs. My approach would be to keep a global map/array of which SKUs are assigned to which bay and vice versa. If an item arrives and it's SKU is not in the list yet, it gets assigned to the bay with the least SKUs and/or items assigned so far. If it has been assigned, you look for a slot in the corresponding bay.

When an item exits, check if it's the last one of that SKU in the storage. If so, reset the SKU-bay-assignment, so the next item with that SKU could be assigned an emptier bay.

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capture1.png (142.5 KiB)

double-dept-asrs-storage-1.fsm (5.0 MiB)

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