Processor setup and dispatcher

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Mischa Spelt asked Aug 14, '17 Mischa Spelt commented Sep 28, '17

Processor setup and dispatcher

Today I was demo-ing the Dispatcher in combination with some processors with a setup time, and had some ... unexpected behavior. It seems that the processor is looking for an operator to do the setup too early. At that point the operator who brought the flow item to the processor is still busy unloading, so the dispatcher does not consider it as available. This regularly has the effect of one operator bringing a box to the processor, then another operator coming over to do the setup, while the first one is standing by idly. See the attached demo model - you can see the effect at the third box (processor 1) already.

Turns out it works like this at least in the 17.2 beta and in the current LTS, so not sure it qualifies as a bug, but it surprised me a bit nonetheless. If you wanted you could probably use pre-empting or Process Flow to work around this, but would you not want to release the operator first, then start the setup, so that the freed operator qualifies for the setup task?

Software Version:

FlexSim 17.1.4

processor operators dispatcher setup time

operatorreleasedtoolate.fsm (21.0 KiB)

Answer 1 · 2017-09-28T13:56:51Z

Phil BoBo answered Sep 28, '17 Mischa Spelt commented Sep 28, '17

This has worked this way since we optimized the objects' events for version 4.0 in May 2007. During the unload task, the item enters the processor. During the entry of the item, the processor begins its behavior. This all happens immediately without extra events between each step (so the setup starts before the unload task has completely finished). All of the objects work this way, minimizing the number of events added to the event list. This helps improve model run speed, and we have many different solutions for getting around the peculiarities of this system (such as this one) that can be applied in one-off cases rather than always being applied, even when unnecessary and inefficient.

For this particular case, we added the Tagged Resource pick options so that you can explicitly assign the resource that carried the item to be the same one that is used for the setup. You could also create a custom task that combines the carrying operation and subsequent steps into the same task sequence. We used to teach this mechanism as part of our basic training classes. More recently, you can get even more control over your operators' allocations and task sequences by using Process Flow logic, which is what we teach now.

We are not planning on "fixing" this. This is working as designed, and we have implemented lots of features into FlexSim for handling this type of situation.

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Mischa Spelt commented · Sep 28, 2017 at 02:26 PM

Thanks, I never did notice / understand the Tagged Resource option. Makes sense now.

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