question

I built something like this using a combination of labels and trigger functions on the conveyor and a decision some time ago.

The decision point is responsible for stopping further items if the next target batch is reached until it receives a message from the exit conveyor which resumes any waiting item. The decision point has the following labels and trigger logic:

The "QtySequence" and "SequencePos" determine how many items should be let through. Each time an item continues past the decision the "CurCount" label is incremented. If it reaches the target number, the SequencePos is increment (1 -> 2 -> 3 -> 1) and the counter is reset. Additionally, the "StopNext" label is set to 1. This has the decision point stop the next item in the arrival trigger (so before the On Continue trigger). The Conveyor.Item reference is also written to label, so the On Message trigger has access to that value and can resume the stopped item once a message is received.

The exit conveyor has the following logic attached:

The first two labels serve the same purpose as on the decision point. They determine if all items of the current batch have reached the end of the conveyor in the On Item Bump trigger. This then causes the input of the connected queue to be opened, so the items can exit the conveyor. (You can use many different ways of moving the items from the conveyor: push them to a list, create task sequences, implement this logic in a process flow by listening to the item bump event in an event-triggeres source, ...)

When the last item is exiting the conveyor, the On Exit trigger closes the input of the queue again and sends a message to the decision point, letting it know that further items can now continue.

Finally, in this example, the input of the queue is closed in its On Reset trigger, so it starts the model in a closed state.