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Alexander Swinarew avatar image
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Alexander Swinarew asked Alexander Swinarew commented

Equipment pulling material from ASRS via Conveyor

Hi,

I am currently a bit struggling with a scenario and hope that you might give me some idea on how to model it.

The scenario looks as follows. Material is stored in the ASRS. Afterwards, it is brought via conveyor to drop points which act as a form of buffer. The material is then picked up by AGVs from the drop points and transported to the machines. The small light green rectangles are those machines that process the material in form of lots that are separated into 2-4 boxes.

I would like to implement a pull logic where a machine, e.g. the one marked in blue, pulls material as soon as it is idle from the ASRS which then sends it via conveyor to the correct drop point and from there via AGV to the correct machine.

What would be the best way to approach this?

Another issue that I see is the handling of lots consisting of up to 4 boxes, i.e. transporting to the same drop point, machine etc.

Maybe you could give some insight to this point as well.

Thank you in advance!

Alex

FlexSim 20.0.3
flexsim 20.0.3lot handlingpull logic
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tannerp avatar image tannerp commented ·

@Alexander S7,

I am following up on this question to see if there's anything else you had questions about? If you felt that the example model helped, please click "Accept" on the answer. Otherwise, feel free to comment back with more information. Thanks!

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Alexander Swinarew avatar image Alexander Swinarew tannerp commented ·

Hi Tanner,

First of all thank you for your comprehensive reply and the model. I was unfotunately occupied with other topics and did not manage to look at you model in more detail. I will do that the coming week and get back to you with any open questions that I might have.

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tannerp avatar image tannerp Alexander Swinarew commented ·

Thank you for the update, @Alexander S7.

I will un-accept my answer for now so this question stays live. Feel free to comment back with questions whenever they arise.

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1 Answer

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tannerp answered Alexander Swinarew commented

@Alexander S7,

I took the liberty of building out a small example as I felt that it would probably answer more questions on its own than a long text answer from me. The idea behind this model is that there are tokens that represent each of the machines. These tokens pull items from the ASRS rack, transport them to the conveyor belt, and then to the machine. I also added a "Type" label to items and processors so that multiple items of the same time can be processed simultaneously. I hope this helps. Let me know what specific questions you might have about this model.

asrs conveyor model example.fsm


asrs-conveyor-model-pf.png (33.6 KiB)
asrs-conveyor-model-example.fsm (69.7 KiB)
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Alexander Swinarew avatar image Alexander Swinarew commented ·

Hi Tanner,

I tried the approach where the different machines pull directly from the list with the pull requirement that the processID saved on the equipment matches the processID saved on the items as labels. I modified the code and it works until the point where the number of requested/required items is required. Since the number of boxes per lot varies with each product, the requested number of items varies accordingly. I have trouble assigning a dynamic value for the requested number, e.g. based on the label "boxesPerLot" that is saved on the items. Is there some work around for this? Otherwise I will try to solve it via process flow.

Thanks and best regards,

Alex


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tannerp avatar image tannerp Alexander Swinarew commented ·

@Alexander S7,

You can assign the "boxesPerLot" as a label to the processor or you could go the Process Flow route. If you have a model you're working with, I'd be happy to take a look and figure out a solution. Feel free to post it here.

In the meantime, I will adjust my example model to have a dynamic lot number in case it's helpful.

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tannerp avatar image tannerp Alexander Swinarew commented ·

@Alexander S7,

Here's an updated version of the example model. Hopefully the attachment works (we've been having issues with our Answers website recently). Let me know if this would work for your needs. The lot size label is assigned to the tokens and then affects how many items are pulled. You could assign the label from a table or otherwise, but I just used a duniform() function for the sake of example.

asrs-conveyor-model-example_1.fsm

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asrs-conveyor-model-example-1.fsm (69.6 KiB)
Alexander Swinarew avatar image Alexander Swinarew commented ·

Hi Tanner,

Thank you for the reply. I use the following code in the pull strategy field. It is basically the standard pull from list code with some minor modifications.

I wanted to use the label carrierPerLot stored on the processor as the number of requested/required items. However, the label value for carrierPerLot is assigned in the pull requirement itself (second screenshot). So when I reset the model, the carrierPerLot is at 0 and that is when the pull requests are apparently created and sent to the back orders. When I then start the model run, the carrierPerLot is accordingly at 0 and the requested/required is also at 0 and the pull does not go through.

There are 85 different products that come in different sizes in terms of carriers per lot. So I cannot assign a fixed request number unfortunately.

I am not sure if is possible to set the carrierPerLot label in a way that the corresponding number of boxes are pulled from the list.



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tannerp avatar image tannerp Alexander Swinarew commented ·
@Alexander S7,

Thanks for providing some more information. It's a little difficult to understand how the model is working without seeing it. You can dynamically set the carrierPerLot label using the items, but I think you'll run into problems because if you're changing the number to pull with each item, then you're never going to reach the designated number. Does that make sense? For example, if the first item comes in and wants to have 5 items in its lot, it will set the value to 5. Then, when the next item comes in, it might only want 3 items in its lot, which means the first item wouldn't get its last two items. So I don't think dynamically updating it based on the items will work.

Have you reviewed the Process Flow example? In Process Flow, you can set the tokens to represent "orders" or "lots" that pull a certain number of items. This way, you're not going to have items confusing the lot numbers every time they move around.

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Alexander Swinarew avatar image Alexander Swinarew commented ·

Hi Tanner,

Please find attached a small scale version of the actual model. I hope this helps understanding my model.

ASRStoDPtoRackToEQ.fsm

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asrstodptoracktoeq.fsm (148.2 KiB)
Alexander Swinarew avatar image Alexander Swinarew commented ·

Hi Tanner,

I reviewd the process flow approach and tried to model it accordingly, but it seems that there are still some issues that I was not able to resolve. I would greatly appreciate if you could take a look at the revised model.

I tried to use the information from the lots that are created throughout the week as a reference for the requested/required items. There are two lists. One for the lots and one for the actual items. The equipments pull from both lists. First the lot and afterwards the boxes that are associated with this lot.

Thanks and best wishes,

Alex

ASRStoDPtoRackToEQ_9.fsm

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asrstodptoracktoeq-9.fsm (154.2 KiB)
tannerp avatar image tannerp Alexander Swinarew commented ·

@alexander.s7,

I apologize for the delayed response to your questions. I noticed that your comments were actually posted as "Answers" to your original question, so I didn't see them. Please double-check next time you comment that you're writing a comment and not an answer so I can get back sooner.

Now, to help answer the question: It sounds like you're looking for a method to pull all of the items associated with a given lot. Is this the main question you have? Or is it about how to push the items to one list and a reference to the items to another list?

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Alexander Swinarew avatar image Alexander Swinarew tannerp commented ·

@tanner.p

No worries. A lot consisting of multiple items (e.g. 2 or 3 boxes) has to go through several processes. There are different products for which multiple lots are created evenly distributed throughout the week. The items are supposed to go from ASRS to the equipment via a drop point (small buffer) and after processing back to the ASRS via the same drop point. Therefore, I tried to use a process flow where a token representing a lot is created as soon as the respective lot is created and which is then pulled by one available machine. Additionally, the machine has obviously to pull also items associated with the lot. Afterwards the lot has to go back into the list and can be pulled for the next process by another machine.

The last model that I posted represents my attempt to reproduce this logic.

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