Find Empty Pallet in Rack

[stayhometown]

Hi everyone,I was working on a picking model.

After packing, the operators will move the whole pallet into rack.Then,they will start picking boxes to Queue1. Meanwhile I want my operators also keep searching the empty pallet and move them to Queue2 as soon as they appear.

My problem is that the find item process couldn't find the empty pallet while I already add my query clause like this:

 Could someone help me figure out what happened?

Here's the model.Thanks.

[moehlmann_fe · Accepted solution]

When the token enters the Find Item activity, the query is evaluates against all items in storage. After that point only newly entering items are evaluated. 

Instead of using Find Item you can just check if the pallet is empty each time an item is loaded. If so, create an extra token that controls the transport of the pallet.

[stayhometown]

Hi @moehlmann_fe big thanks for helping me. Though I still have a few questions about your reply.

When the token enters the Find Item activity, the query is evaluates against all items in storage. After that point only newly entering items are evaluated. 

Could you explain more detail about this ? 

If the query evaluates all items in storage,then why only the newly entering items are evaluated? I thought all items in the rack could be detected by query whether the item is newly entering or already in the rack?

Besides I'm also confused about this one. I thought the quantity input field should fillin a value,but this looks like a conditional expression. How does this work?  

[moehlmann_fe · Accepted solution]

When the query is first run the pallets are still full and thus do not qualify for the condition. When a new item enters the storage, the query is only evaluated against it to safe performance. FlexSim is a Discrete-Event-Simulation software. It is based on reacting to events in the simulation. An item exiting the pallet is not something that would cause the query to be reevaluated by default. It is up to you to determine a good event to react to when you are waiting for changes in the simulation.

The same would be true if you wanted to find an item with a specific label value. The label of an item already in storage changing would not be detected automatically.

As I said, in this case you know when a change occurs - when the load task finishes. So you can then check if the condition is now true and remove the pallet.

A condition can be used as a stand-in for a number and vice versa. "True" becomes 1, "False" becomes 0. 0 is in turn interpreted as false, whereas any non-zero number reads as true.

If you wanted to use a different quantity when the condition is true you could use the expression "condition ? (value if true):(value if false)"

[stayhometown]

Got it!Thank you very much,I have learned a lot from your answer.