Thank you for your help and input.
I think I got somewhat closer to what I really would like to simulate. Unfortunately, I still think that the pull control is needed.
When "Bearbeitung" pulls a MU from "Supermarkt_Bearbeitung", a Kanban card will be sent to "Ausgangspuffer" so that a new MU will be produced/ will be prepared to be transported.
Then, the MU is supposed to be pushed from "Bearbeitung" to "Zwischenpuffer".
I think it's the easiest to show you by uploading a sketch.
Hopefully, that explains it better.
However, both versions (29_06 and 30_06) don't work properly.
- In the first version, the MUs don't get pushed from "Bearbeitung" to "Zwischenpuffer" and for some reason one Kanban remains in the Kanban buffer.
- In the second version, no Kanban cards are being created when an MU leaves "Supermarkt_Bearbeitung" at first. Later on, it does work though.
I'm sorry that it's such a mess. I would highly appreciate any kind of help.
one basic remark: the most important principle in KANBAN systems is: no movement without KANBAN !!
In your sketch you have a 3 stage-kanban-system, so you need 3 kanban-loops.
So you need to remove the (production) kanban from the bin in Zwischenpuffer and send it back to Supermarkt_Bearbeitung. Then you has a closed KANBAN system. Maybe it would be good to differ between transport and production kanban, like in the most practical systems.
here you have a simple three-stage KANBAN-system. It is much simplier as you think.
Some remarks: the loops are not connected by connectors (because the kanban trigger the material movement), you had a failure in the kanban-control; only at the (now) Kanban-buffer0 you will create new (green)parts. In all other steps, you move bins from the buffer. You need also an initial stock in Zwischenbuffer (in your subframe).
The KANBAN controls are quite similary: wait for stock (possibly also for production capacity), remove the kanban, send it to the previous step, add the triggered kanban to the bin and move the bin from the buffer to the next step (no connector!!!).
Then the material is running using connectors until the next buffer. There the next kanban-loop starts...
Thank you for the explanation and the new model.
I just have a few questions remaining; some to clarify that I understand it correctly:
1.) Why is it a three stage-kanban-system from your point of view?
- When MUs are moved from "Supermarkt_Montage" to "Senke" the kanban card will appear in "Kanban_Puffer2"
- When MUs are moved from "Zwischenpuffer" to "Milkrun_2" kanban cards appear in "Kanban_Puffer1"
Is that necessary to keep track?
- When MUs are moved from "Supermarkt_Bearbeitung" to "Bearbeitung" kanban cards appear in "Kanban_Puffer0"
Did I understand it correctly?
2.) Now, I noticed that "Zwischenpuffer" runs empty before new MUs are moved from "Bearbeitung". Is there a way to move the MUs earlier than that?
3.) Do you know how I can set the capacity of the Kanban_buffers, so they don't miss any MUs. For example if I set the initial inventory to 20 instead, more MUs leave the system (Senke), then I track in my buffer.
I know that I can increase it to a higher number. But maybe, there's a more elegant way.
And you're right. I think I only need transport kanban. This means, that I don't have to create new MUs in Kanban buffer 0, do I?
I'm sorry that it's still such a mess and thank you very much for your constant help!
"1.) Why is it a three stage-kanban-system from your point of view? "
- look at your sketch, you have 3 loops
"2.) Now, I noticed that "Zwischenpuffer" runs empty before new MUs are moved from "Bearbeitung". Is there a way to move the MUs earlier than that?"
- you need to balance your production; your capacity needs to fullfill the requirements of the drain (check the ProcTime of the drain and the production), the transport times you need to overbridge with buffer stocks; this is one of the main principles of KANBAN systems
If you want to move material earlier (without KANBAN), then it will not be an KANBAN system anymore.
"3.) Do you know how I can set the capacity of the Kanban_buffers, so they don't miss any MUs. "
- try to calculate the buffer capacity from the duration of the milkrun and the consumption of the drain (+ safety stock).
"And you're right. I think I only need transport kanban. This means, that I don't have to create new MUs in Kanban buffer 0, do I?"
you need to create new MUs at the start of the simulation (could be also a source). The KANBAN in Kanban buffer 0 triggers then the transport of this parts, the KANBAN that is triggered the production would be a production kanban
Thank you for the answers!
I tried to implement the version with just transport kanban and a source. Here, I said that Kanban buffer 0 would be the trigger of the source. However, now I ask myself how it would be possible to have like a daily delivery from the source to the first buffer and then start the kanban loops/system.
Another thought which came to my mind is that wouldn't it also makes sense to switch the bin and Kanban in terms of their objects. Bin as an MU and Kanban as a "Förderhilfsmittel"?
I also simplified the "init method" as you don't need the lists anymore, do you?
I tried to switch the kanban and bin. At the first buffer, it does work to some extent. But after that, I'm just not quite sure how to address the kanban card as it is now a "Förderhilfsmittel". Do you know how I could address, so that it is moved instead of the MU? I wasn't able to find anything in the help function.
Secondly, I tried to change the exit control of buffer 0 to a "transport kanban". The only problem is, that the kanban card shouldn't just disappear, but go to the new part. Am I wrong by thinking that?
Thirdly, I put a storage unit at the beginning. There, I tried to use the example of your book. However, I always get the following error: "Unbekannter Bezeichner holeFreienPlatz" in the method "einlagern. Do you have any idea what the reason could be?
I got it done so far, that only the Kanban as "Förderhilfsmittel" are moved.
My only problem is now to combine the Kanban card with a new MU created by the source.
My idea is to use a method at the exit control of the source to "waituntil Kanban_Puffer0 is occupied". The same goes for the exit control of Kanban buffer 0, namely to wait until the source creates a new MU before moving the Kanban card. And then to put the new MU on the "Förderhilfsmittel".
Unfortunately, my program keeps either crashing or not working when I tried that.
That's why I attached a version right before that where everything works until it reaches the last/first Kanban buffer.
I think this is the final step and it would be a huge help.
Thank you very much,