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-   -   Problems with load/ unload tasksequences (https://archive.flexsim.com/showthread.php?t=1153)

Sebastian Hemmann 11-18-2009 02:55 AM

Problems with load/ unload tasksequences
1 Attachment(s)
Hello all,
I´ve got a problem with building up a modell in which the following works:

An Operator walks to a queue(WA_1), if there is anything inside, it would collect as much as possible and walk to the next queue(WE_2). There it unloads only the items with an specific itemtype/label. From there it goes on, to another queue (WA_2) to load again as much as possible. After this the Operator travels to the next queue (WE_3) and unloads again the specialized items. On the queue (WA_3) it loads the last time in this round and goes to queue (WE_1) to unload. Then all begins again.

I tried different ways the last days and still don´t find a way that really fits.
My concrete problems are:
If I only use Tasksequences for all of this, the Operator never loads more than 1 item and shows problems, if the content of the queues is "0".
I found another way, where the Operator allways takes the same item from wherever. Couldn´t figur out why.
In the modell I attached, the way of the flowitems is set by collected ports and the way of the operator is set with a createt tasksequence in "Request Transport From" Picklist. This nearly works the wright way. Purely it sometimes stops. The Operator don´t always stops at the next "WA_" queues to load, or "WE_" queues to unload.
The dispatcher(Verteiler) is in the modell, because in the later modell there will be more stocks and more operators.
Got some different modells builded and could load up another one, if this makes sense.
Hope anyone can help me or even give me a great idea.
Thanks a lot even before.

Sebastian Hemmann 11-18-2009 03:26 AM

Just forgot something
I just forgot, that WA_1 and WE_1 even as the others in reallity are one stock. I splitted them for the modell with hope to make things going easier.
So if it is easier to make the operator unload at first and load from same station, this would be helpfull

Tom David 11-18-2009 04:11 AM


I did not have a look into your model, but it sound familiar for me what you are trying to do.

In the download section you can find a model (Sample_PickOperatorTravelsThroughNetwork_TD) where I did, what you trying to do, as far as I understand it right. Have a look into the description which will give you some hints and help (hopefully).
There is another model (Sample_PickPlaceOperatorsTravelThroughNetwork_TD) which is based on the first model but not only pick also place is done.

I guess I faced a lot of problems when I made this models which you are facing now.
For example, that the operator always takes the same item. This is a pointer problem and it is important in a task sequence to point to the right item. I solved this in my models and as you can see but this is quite some heavy stuff. I store pointers to the items when they are arriving in the queue in the tree to be able to get the once which needs to be loaded.
In general what I do in my models is at the Network Node of a queue to check if there are items which needs to be picked. If this is the case I generate the task sequence to pick them. At the last network node I generate the task sequence to deliver all items in the operator to the destination.

Anyway, I hope the model is helpful for you. Good success!

Sebastian Hemmann 11-18-2009 04:23 AM

Thanks Mr.David for fast help, will see if I can handle with this information. I tried to find out how you solved the problem with your "Milkrun" modell, but there had been to many other query in it.
Allready thought, that it is an pointer problem, that the operator allways takes the same item, but couldn´t find out how to solve.
Since days I experiment and search in this forum but couldn´t find out what me really helps.
Thanks again.

Sebastian Hemmann 11-18-2009 04:51 AM

What I´m trying to do, looks an little bit different. The idea is a modell of milkrun in which on every stop specific items get unloaded and other items (probably empty containers or even other items for other stops) get loaded. The pointer to the items will be very helpfull, thank you for this information. Just hoped to find something like a milkrun modell with return of empties.

Tom David 11-18-2009 08:11 AM

To be honest, the two models I mentioned are concept models I build before I build a milkrun project model. Even if they are not called Milkrun-Models the idea behind it is a milkrun system.
There is another model in the concept models which is a milkrun model (Sample_MilkrunKanbanSystem_TD) but I am pretty sure, you alread found it.
The concept in this model is different. Here the Milktrain (transporter) takes all items from one queue and bring them to the destination. The items (pallets) are generated based on some logic, which is that if a pallet leaves at a queue (close to process) a new pallet is placed in the input queue.

In the first two models I mentioned the items arrive randomly in queues and the milktrain (operator) needs to check if he should take an item or not.

In the project model the processors demand material which will be put into queues and the milktrain takes them and brings them to the processors. If there are empty pallets at the machine he needs to take them.
So I guess my two models are close to what you are trying to do, but it is quite some code behind it and maybe not really easy to understand what is done where in the code.
That's why I always first build a concept model for myself to understand which modeling concept I like to use, before I start with the project model. Most of the models I uploaded here in the community are such models. Sometimes I wish more people would do the same, because we would have a great source for different model concepts, but unfortunately not a lot of people share their conecpt models or do not build such models.

Anyway, I hope you will figure out how to solve it in your model. But I hope I pushed you in the right direction.

Tom David 11-18-2009 11:55 PM

1 Attachment(s)

I had a look into your model and modified it a bit, how I would start to solve your task.
During building this model I remember now why I do all the checking in my models (PickPlaceOperators).
Tasksequences are really powerful and overrule “normal” Flexsim mechanism, that’s why a lot of checking is needed.
My little model I will attach is just a start and very basic. I put some comments into it, but like said a lot of work needs to be done. It is a tricky problem.
And by the way, next time I would start to build my own model, because some of the stuff you already put into your model, made me search for some strange behavior which was based on your code. ;)

Anyway, try to understand what I am doing and how I started with the model.
I guess a good idea would be that you give me a call if you like to discuss your task. If I would try to write down all my thoughts and ideas, I guess it will be a book.

I think you have my telephone number, otherwise you can find it on the German Flexsim Homepage.

I like to help you, because I guess this is a task more people need to solve and maybe my uploaded models are already too complicated to understand. So I hope in the end that you will upload your concept model and this hopefully will help others.

By the way, the library from Brandon Peterson is in my eyes very helpful if you work with tasksequences.

Sebastian Hemmann 11-19-2009 12:58 AM

You are wright, there had been some query in my modell in which I tryed out to solve with labels. It is allways hard for others to find out what the modell builder has done and why. Even if I don´t give a clear description with it.
Will give you an call later.
Hopefully to create and load up a modell which don´t only helps me.

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