topic Re: Help with "Wait for Event" / "Synchronize" Function in FlexSim Forum

Help with "Wait for Event" / "Synchronize" Function

svedullapalli — Tue, 29 Jul 2025 21:56:16 GMT

Hello,

I am trying to model the following:

PL enters Station PLPLA -> Some work to be performed on PL -> Once PL work is completed PLA enters (PL is still in station) -> Work is performed on PLA and PL when both are in station -> Both PL and PLA are moved to Stock after work is completed

I have used "Wait for Event" function with On Exit referencing PLPLA Delay for PL. By doing this, The tokens are getting stuck at PLPLA Acquire for PL.

Can I get help on why this is happening? Also, is there a better way to model the scenario I laid out?

Re: Help with "Wait for Event" / "Synchronize" Function

moehlmann_fe — Wed, 30 Jul 2025 06:58:32 GMT

Both tokens want to acquire PLPLA1 of which there is only one copy. You describe the process as being sequential, so it should be modelled that way. A good way to wait for the second item to be available is to use list.

Instead of delays you should always wait for the "On Process Finish" event of the current processor to guarantee that the Process Flow and 3d model stay synced (in case you change to random process times).

Is it on purpose that the processors can hold any number of items while they wait to enter the next station? Because otherwise the previous resource should only be returned after the item was moved.

Re: Help with "Wait for Event" / "Synchronize" Function

svedullapalli — Thu, 31 Jul 2025 16:50:56 GMT

Thank you so much for your response. Your solution helps with the logic I was trying to build.

Also, answer to your comment "Is it on purpose that the processors can hold any number of items while they wait to enter the next station? Because otherwise the previous resource should only be returned after the item was moved." - I missed logic into that. I would like the item to enter only after the other item leaves. What is the best way build that into the process flow?

Image below is from your model.

Re: Help with "Wait for Event" / "Synchronize" Function

moehlmann_fe — Thu, 31 Jul 2025 18:13:23 GMT

To prevent items from entering an occupied processor only release the previous resource after the next one has been acquired. To make that work properly either use different label names when acquiring each resource or make sure to set the Release activity to release the "First Acquired" resource.

Re: Help with "Wait for Event" / "Synchronize" Function

svedullapalli — Fri, 01 Aug 2025 20:33:55 GMT

Hi,

I changed the Release activity to release the "First Acquired" resource. That doesn't seem to be working. Also, I tried using "Wait for Event" with reference to Object "PLA Station 3" and On Content Change to Arrive at Value 0. That also, does not work.

Re: Help with "Wait for Event" / "Synchronize" Function

moehlmann_fe — Mon, 04 Aug 2025 06:30:17 GMT

In the Wait for Event activity you would need to activate the "Fire If Initial Value Meets Rule" checkbox, so that a token can continue if the next processor is already empty when it reaches this point.

In the attached model I rearranged the Release activities to prevent items from accumulating in the processors.

Re: Help with "Wait for Event" / "Synchronize" Function

svedullapalli — Mon, 04 Aug 2025 13:48:30 GMT

Thank you so much @moehlmann_fe ! This helps!