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Q&A Using Flexsim and building models

  #1  
Old 02-19-2013
Gavin Douglas Gavin Douglas is offline
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Default lots of WIP

Hello,
I’m modeling a very high volume process which creates large amounts of inventory in FlexSim. In fact, FlexSim will grind to a halt after running the model only a few short minutes. So I got the idea to use a variable to keep track of the wip levels like:


On entry>

wiplevel++; <<global variable

Destroyobject (item);

Now I have a count of the inventory with nothing for FlexSim to render. However, for the downstream processor, I need to detect if the wiplevel >0 and create some sort of flow item for the processor “use.” Any idea how to do this? Thanks…

btw, I did uncheck the "show contents" tab and it helps only a bit.
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  #2  
Old 03-13-2013
Kris Geisberger Kris Geisberger is offline
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Default

If you are using Queues, you should try changing the Item Placement to "Do Nothing" as that can have a significant impact.

Your idea is a good one. There are many ways to go about it, I usually end-up not using port connections from the inventory locations to their destinations in these type situations, mostly because there is usually some sort of centralized transport dispatching logic anyway. In those cases I would use a global table to store inventory counts by location and type, then decrement the count and create the item just before I send a TE to pick it up. Using transfernode() you can avoid executing the OnEntry trigger of the inventory.

Back to your question - To keep with standard connections routing logic I think it would be easiest to always have one flowitem released (on-deck) to be accepted by any of the downstream objects. The attached model has 2 examples using a BasicFRs that I called "LeanStorage". The blue storage object uses standard transport logic, and the other does not. Both assume that you are only storing one type of item per location, but its enough to demonstrate the concept.

I used 2 labels on the LeanStorage for Capacity and CurrentContent, but again you could use tables, global variables or even tracked variables. If you are concerned with speed I would use ranks instead of strings like I did for the labels. Also, I would likely create a global pointer to the master flowitem in the flowitembin instead of referring to it by string like I did (see either OnMessage or TransportDispatch code).

Oops, let this be a reminder to both of us... SEARCH before you post! A year ago Phil posted an example using a Queue (he faked the visuals nicely too):
http://www.flexsim.com/community/for...ead.php?t=2131

I'll still post because I have an example using transport, and others learning the BasicFR might find it useful. Caution: I did nothing in regards to state management so the state profiles are not representative at this point.
Attached Files
File Type: fsm LeanStorage v6.02.fsm (72.1 KB, 73 views)
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