question

Vasile avatar image
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Vasile asked Felix Möhlmann commented

Conveyor switch lane using two rotating tables - shortest queue

Hi all,


New to FlexSim, been having a hard time trying to get the below model to work.

There are two sources that each create flow items on two separate conveyors.

Each conveyors has it's own rotary table.

The rotary tables should connect with each other and transfer the flow item based on shortest queue, hence why i added the station on conveyor3, to create a backlog that would allow Rotating1 to connect to Rotating2 and then send the item to conveyor5.

Having difficulties aligning the entry and exit points on these to move at the same time when an item needs to be diverted.

Simple model below.


Lane switch shortest queue rotating table to rotating table.fsm

FlexSim 25.1.0
conveyorsystemrotating and transferring items
lane-switch-shortest-queue-rotating-table-to-rotat.fsm (49.5 KiB)
5 |100000

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1 Answer

Felix Möhlmann avatar image
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Felix Möhlmann answered Felix Möhlmann commented

With how the tables are set up, you need to synchronize their tasks when an item switches conveyor. Currently the table just loads the item and unloads it to the second entry transfer, thus rotating to face the transfer. The order of operations would need to be (table1 loads item -> table1 does placeoffset task with table2 as station | table2 does pickoffset task with table1 as station -> table2 loads item from table1 -> table2 unloads to entry transfer).

While you could do this by constructing a coordinated task sequence in the exit transfer's Use Transport field, I would recommend to use Process Flow to control the tables.

In the attached model I let the tables only travel the y-coordinate in the pick/place offset task, since the x-coordinate of the item should not change. You might have to implement the Pick Place Offset trigger of the tables to return the correct coordinates for the general case.

lane-switch-shortest-queue-rotating-table-to-rotat_1.fsm


lane-switch-shortest-queue-rotating-table-to-rotat.fsm (62.1 KiB)
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Vasile avatar image Vasile commented ·

Thank you, Felix. Process Flow on conveyors with rotating tables is one thing that i wish to master soon.

I've one more scenario which is bothering me:

- One more source (3) created leading into the rotating table 1

- I would like to have both the rotating tables feed into each other, in case their conveyors (3 or 5) become overloaded at one point. Now only table 1 is offloading into table 2 and then moving to conveyor 5.

- Source 3 feeding into table 1 should be working on the basis of first arrived first acquire the table 1 or 1 & 2, in case it will need to offload to conveyor 5 directly, as maybe conveyor 3 will be overloaded. For that reason i've put two decision points at the beginning of table 1, but it's still probably going to need process flow. Not sure if an acquire zone would work here, or simply building upon the already provided solution.

lane-switch-shortest-queue-rotating-table-to-rotatingtablebothways.fsm

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lane-switch-shortest-queue-rotating-table-to-rotat.fsm (150.4 KiB)
Felix Möhlmann avatar image Felix Möhlmann Vasile commented ·

The logic needs to be adjusted a bit (starting the task for both tables at the same time when an item needs to cross) to prevent a deadlock where both have an item loaded that needs to move to the other table.

Other than that you can keep using the same Process Flow. Where the item is send is still decided by the Exit Transfers. The Process Flow only facilitates the transport.

The flow only works for two tables currently. (The decision is binary - does the item go my main outlet (first centerport connection)? If not, move it to the other table and have it unload to its main outlet). If you wanted to chain three or even more tables together, you would need to provide different means of identifying where the table needs to move the item to.

lane-switch-shortest-queue-rotating-table-to-rotate-2.fsm

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lane-switch-shortest-queue-rotating-table-to-rotat.fsm (151.6 KiB)