Prossesor pull from Queues issue

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SaiKrsih asked Feb 28, '23 SaiKrsih edited Mar 2, '23

Prossesor pull from Queues issue

Hello Flexsim Answers group,

In my model (below attached), a multiprocessor gets items from two Queues, such as Q1 and Q2, and processes them before sending them to Q3.

Where, Q1 receives 100 items with an interval of 5, 15, 25, and 35 minutes.

Similarly, Q2 receives 25 items with an interval of (0,10,20,....min)

In this case, I am utilizing a "Source" activity in the process flow to replenish the Qs, but in my actual model, these Qs (Q1 n Q2) receive items from other Qs that belonged to other processors.

Both Qs flush out only if they reach a limit/batch size of 100 items

In this model (attached), Q1 receives a batch of at least 100 items on each interval, whereas Q2 only receives 25, so it waits and flushes until it hit the limit of 100. Even though, Q2 hits the limit of 100 the processor is not pulling from Q2 due to the ongoing minimum replenishment at Q1 with 100 pieces every time (on each interval). Because of this the processor only pulls from Q1.

I would like to know how to make a processor pull from Q2 when it hits its limit by halting Q1, and when Q2 does not reach its limit, the processor should pull from Q1

Any recommendations?

Machine pull issue.fsm

Software Version:

FlexSim 22.2.2

processor pull

1677604235938.png (155.4 KiB)

machine-pull-issue.fsm (1.2 MiB)

Answer 1 · 2023-02-28T17:25:22Z

Jacob W2 answered Feb 28, '23 SaiKrsih edited Mar 2, '23

Hi @SaiKrsih,

I have made a couple of small additions to the model you posted. I added an event triggered source that generates a token when Q2 finishes collecting 100 items. This token then closes Q1s port and waits until Q2 has released all of the items it collected before opening the ports on Q1 again.

machine-pull_JW.fsm

machine-pull-jw.fsm (52.8 KiB)

· 3

SaiKrsih commented · Mar 01, 2023 at 09:05 AM

@Jacob W2 I appreciate your response. It functions effectively. Now I made some adjustments such that I raised the quantity of products at Q2 from 25 to 100 items on every intervel. This indicates that both Qs receive 100 items and both exceed the limit simultaneously.

Even though the items from Q1 (yellow boxes) are pushed on to conveyers. The processor is stopping the flow of the items from Q1 and pulling from Q2 when I run the model.

I would like to know how to instruct the processor that after processing a batch of items from Q1 it should pull from Q2 and viceversa. (Like a batch from one Q after the another in a circularway)

Please help me to solve this issue

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1677661057182.png (197.1 KiB)

Felix Möhlmann SaiKrsih commented · Mar 01, 2023 at 09:59 AM

You seem to misunderstand a couple of things or rather have wrong expectations:

- The Pull Strategy of the processor currently has no effect. A Pull Strategy only ever affects the immediate upstream connection. Both the processor's input connections connect to the same Exit Transfer of the conveyor. So it can only ever pull the item at the end of the conveyor.

- The queues release their items onto the connected conveyor as soon as there is space available.

- Conveyors connect to each other without the need to place port connections (no ill effects if you do in most cases, but nonetheless a lot more convenient to not use them in my opinion)

So to control the order in which items are processed you have to control the order in which items arrive at the end of the conveyor. Jacob did this by closing the output of the queue. You could expand this logic to both queues, such that each queue closes its output until X number of items of the other type were received by the processor.

In the attached model I demonstrate another approach that uses Photo Eyes (Decision Points would also work) to control the item flow at the conveyor intersection. After a number of items equal to the "BatchSize" label have passed a Photo Eye, it stops the next item. It then also sends a message to the other Photo Eye to let it know that it can now resume its own stopped item, if there is one.

machine-pull-issue-fm.fsm

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machine-pull-issue-fm.fsm (50.6 KiB)

SaiKrsih Felix Möhlmann commented · Mar 02, 2023 at 08:37 AM

@Felix Möhlmann Thankyou very much for the response and its working well. I haven't used this object Photo Eyes so far, it looks pretty cool!

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