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Marten Vdr avatar image
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Marten Vdr asked Eric M commented

Extended rabbit chase or TSS cell operating mode

Rabbit chase original balanced_2021.fsm

I modelled a production cell based on the feedback another user got from @Joerg Vogel and @Benjamin W2 on this question: https://answers.flexsim.com/questions/85100/chase-the-rabbit-manufacture-cells-mode.html

This model uses Rabbit Chase, but I want to see what would happen if it used “extended rabbit chase”/” TSS”/ ”Bucket brigade” (there seem to be many different names for roughly the same thing).

Basically, all the operators are different in that they have different assembly speeds per processor. If three operators are working in the cell, at some point two of them get stuck behind the bottleneck (slowest operator).

I figure this might be a better solution than Rabbit Chase: operator 1 (fastest operator) gets assigned to processor 4. When he is idle, he moves through the cell in the direction of processor 3 and takes over the first “work in process” he encounters. The other operator that was working on that item, then moves back to the queue and starts working on a new item.

That way, the fastest operator who is normally most affected by a bottleneck, has no idle time at all.

But I have no idea how to model that.

Secondly: currently I use 4 groups to determine how many operators are working in a given simulation. Group1 has 1 operator, Group2 has 2 operators, etc. Is there a more elegant way of letting the simulation know how many operators it should use?

I would greatly appreciate any help!

Marten

FlexSim 21.0.2
lean manufacuringmanufacturing cells
rabbit-chase-original-balanced-2021.fsm (66.7 KiB)
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Eric M avatar image Eric M commented ·

Hi @Marten Vdr, was Joerg Vogel's answer helpful? If so, please click the red "Accept" button at the bottom of their answer. Or if you still have questions, add a comment and we'll continue the conversation.

If we haven't heard back from you within 3 business days we'll auto-accept an answer, but you can always unaccept and comment back to reopen your question.

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1 Answer

Joerg Vogel avatar image
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Joerg Vogel answered Marten Vdr commented

This is just an abstract For classic 3D. An operator currently working with lesser efficiency is preempted away from his current utilize task by a higher priority tasksequence. He has got an object connection to an operator with a higher efficiency grade. The FlexSim engine will transfer the preempted utilize task to the higher efficient operator. There are some logic obstacles to conquer. First continuing a utilize task makes only sense if the time to change operators is minimal. The higher efficient operator has to arrive at the processor right before the preempting occurs. If you work with more efficient operators a dispatcher has to manage any transfer for prepared operators. The preempting tasksequence brings the operator to start working on a new item.

At the end you will run into a balanced score card forecast. You have to decide when travel time and rest process time leads to the maximum benefit.

You will certainly adjust dynamically priorities of running tasksequence to decide which operator can be preempted away from his current utilize task.

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Joerg Vogel avatar image Joerg Vogel commented ·
A main problem is an already set process finish event in the event list for the processor. If the efficiency rises you have to manipulate the coming process finish event to occur earlier. There are commands to do this.


The only full controllable object, that you can set to finish something is a taskexecuter while he is in an own utilize tasksequence. If you call on him the command freeoperators then he finishes the utilize task Immediately. It sounds a bit weird but the best approach I can come up with is to replace a processor by a stationary taskexecuter and a queue as an exit transfer point. Then you can manipulate dynamically the end for a process finish without changing events in the event list. And that is something you should only do, if you know exactly what is happening In this list.
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Marten Vdr avatar image Marten Vdr Joerg Vogel commented ·

Hi Joerg, thank you for responding so soon!

Am I understanding correctly that this entire model could be made in the 3D view?

You mentioned replacing the processors with stationary taskexecuters, but how could I then change processing times dynamically? Do you happen to have an example model for this?

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Joerg Vogel avatar image Joerg Vogel Marten Vdr commented ·

@Marten Vdr , here is an example. There are certainly some problems wit statistics, timetable or MTBF/MTTR tools. The dynamic adjustment of finish time works. The efficient operator take the job over. I preempt the default operator by a process flow task sequence.

The logic is in the triggers. The "Operator as Processor" is controlled by the On Message trigger.

dynamic_process_finish_end.fsm

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