question

Jeff's model from the other thread always sends the item to the processors. You want to add a condition to the "Send Item" option that checks whether the processor is available or not.

A simple way to do this is to use the content of the processor.

current.outObjects[1].outObjects[1].stats.content.value

"current.outObjects[1]" points to the ExitTransfer. Adding another ".outObjects[1]" thus references the first output of the ExitTransfer - the processor. "stats.content.value" then returns the current content of the processor.

If that value is 0 the processor is available and the item is send there, otherwise nothing happens and the item continues on.

Here it is important to position the Decision Points close to the Exit Transfers as otherwise a second item might arrive before the first has entered the processor leading to the second item also being send to it.

Attached is a model in 19.2 demonstrating this.

Send_If_Available.fsm

Addendum:

If you want to put the items back onto the conveyor after processing you would have to identify them as already having been processed so they are not send to another processor down the line. Adding a label in the Exit trigger of the processors and checking for it in the condition of the Decision Points would a a way to do it.