How to stop item until pallet count reached?

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Cody F asked Jun 11, '19 Joseph Gillespie commented Jun 17, '19

How to stop item until pallet count reached?

I am trying to get my conveyor system to fill up with the correct amount of pallets. However, when I run the model, the system is able to complete a full cycle before the line is full creating a shortage of pallets. How can I get just one station to hold the first item until the correct amount is reached?

Software Version:

FlexSim 19.1.0

conveyor

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Braydn T commented · Jun 11, 2019 at 03:41 PM

Hey @Cody F

Could you upload your model so we could take a look? If it contains proprietary information we can change this question to private.

Thanks!

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Cody F commented · Jun 11, 2019 at 03:49 PM

model.fsm

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model.fsm (13.3 MiB)

Answer 1 · 2019-06-11T22:32:06Z

Joseph Gillespie answered Jun 11, '19 Joseph Gillespie commented Jun 17, '19

Hi @Cody F,

I wasn't sure how to do this with an individual station, but it's fairly easy with process flow.

This process flow creates a token at the beginning of the simulation, waits for an item to reach a specific station, stops the item (and all the items behind it), waits for all of the pallets to be produced, and then allows the items to resume.

Here is the model with this process flow working: modelanswer.fsm

capture10.png (7.2 KiB)

modelanswer.fsm (13.3 MiB)

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Cody F commented · Jun 17, 2019 at 12:39 PM

So this was working as it should until I had to add some more elevators. I'm not sure if they are related or not, but now the model (Elevator3 specifically) does something weird and then production stops around 15000 seconds. I tried to keep the same logic when adding the elevators to avoid issues, but i'm new to the software and I would appreciate some feedback on where I went wrong. model.fsm

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model.fsm (13.4 MiB)

Joseph Gillespie Cody F commented · Jun 17, 2019 at 07:36 PM

@Cody F

Your main problem is that you had one of your "Wait for Event" activities set to assign labels instead of matching them:

The difference between assign and match is that "assign" will give all the waiting tokens a reference to the item that caused the event. For "match", when an item triggers an event, only the token with the matching item label will be released. What was happening with your model was that items were being assigned to tokens at "DP3 Arrive" (which is what should happen) but then at the first "Wait for Event" when an item came through it became assigned to all of the tokens waiting at that activity. Basically you had lots of tokens that controlled a single box, and that is what made Elevator3 freak out and stop working. By setting the first "Wait for Event" to "match" it fixes this problem.

I also found an error that would pop up at time 10556 as the first item reached DP2 by Elevator1. The problem with this is that you had the decision point set to rotate items "OnArrival", but in process flow you also had it set to load the item on to the elevator "OnArrival". Since it can't do both at the same time, it would cause an error. I changed the "Wait for Event" so that it would fire for "OnContinue" instead:

This is what you have the rest of your "Wait for Event" activities set to anyway, so it makes sense for this one to be set to "OnContinue" as well.

Here is the model with both problems fixed: modelanswer.fsm

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modelanswer.fsm (13.3 MiB)

capture16.png (2.9 KiB)

capture15.png (8.6 KiB)

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