Operator not picking closest item

Question

question

Adil M asked Nov 28, '22 Adil M commented Nov 29, '22

Operator not picking closest item

In the model the operators are to pick from the conveyor, however I notice as the volume comes in they start following a FIFO method despite having the min. dist. option selected on the dispatcher. The are letting boxes pass them on the conveyor and going all the way to the bottom of the conveyor to pick packages. I tried testing 'pick prediction' checked and unchecked but that did not help.

Is there something that can be to done to optimize the picking strategy for the operators. In real case scenario the operator will grab two packages closest to them and place them on pallet positions based on type. Then return and repeat the process.

Mech Accumulation Model.fsm

Software Version:

FlexSim 21.2.4

picking stratergy

mech-accumulation-model.fsm (113.0 KiB)

Answer 1 · 2022-11-28T12:45:32Z

Jason Lightfoot answered Nov 28, '22 Adil M commented Nov 29, '22

First of all you are selecting based on distance to the queue by having task 4 involved 1. Is that what you wanted? If you want to select an operator that is closest to the item you should use task2 involved 1.

I think a better approach would be to use a process flow to handle the assignment to operators and the movements.

· 6

Felix Möhlmann commented · Nov 28, 2022 at 02:01 PM

Similar to Jason I see two main reasons to go for a different approach involving a Process Flow.

- Using a dispatcher means that essentially the items are choosing an operator to pick them and not the other way around. This will often lead to inefficient matchings, where an operator might have been better to pick a different item, but the other task was dispatched first.

- This gets exacerbated by having multiple conveyor sections and thus multiple exit transfers. Meaning items will periodically abort the picking when they move past the edge of a transfer and then start a new task when they arrive at the next.

Attached is an example of using a list and Process Flow. The items are pushed to a list when they enter the conveyor. The tokens in a Process Flow, each representing one operator, then pull items from that list, with items being ordered by distance. (The "distance" field of the list is customized to accomodate the model).

Next, the pickup location is determined (approximately, taking into account the acceleration of the operators would be a whole lot more math). The operator then moves there and the item is moved into them (not "loaded" since that would have the operator travel to different location).

After an operator has picked two items, they unload them to the corresponding queue. For this I ordered the queues in a group, so their rank coincides with the item type, which allows for an easy way to reference the unload location.

mech-accumulation-model_fm.fsm

1 ·

mech-accumulation-model-fm.fsm (118.1 KiB)

Adil M Felix Möhlmann commented · Nov 28, 2022 at 08:27 PM

Thank you Felix- in the example you shared I see that in the process flow a loading delay is included however I don't see any unload delay which was a part of the operators load and unload time. Is that considered somewhere and I'm not able to find it or is that something we would need to add? If so, where would we add it?

0 ·

Jeanette F ♦♦ Adil M commented · Nov 28, 2022 at 08:35 PM

Hello @Adil M ,

The Delay activity sets the state as loading, so in the state chart you will see the loading state.

0 ·

1669667703122.png (13.0 KiB)

Show more comments

question

Operator not picking closest item

1 Answer

Write an Answer

Things to know…

question details