Model comparison with pick off vs without pick off

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Adil M asked Dec 1, '22 Adil M answered Dec 1, '22

Model comparison with pick off vs without pick off

Hi, I have two models which represent a packaging warehouse. One model utilizes "pick offs" wherein an operator generates WIP- the scanner would then need to pick the package up and scan it into a pallet location based on 'Type' of package. In the other model the scanners are directly picking 2 packages from the belt and placing them on the pallet position based on package 'Type'.

So the main difference/advantage in the pick off model over the mech accumulation model is
1.) WIP generated on buffer zones closer to where the pallet position for a certain package would be- reducing travel distance.

2.) Lower loading time- since the operator now needs to choose from 12 pallet locations if picking from a buffer as opposed to 60 if picking up from the main belt. The loading time is 3.5 seconds( normally distributed) instead of 4.5 seconds.

Still after running both the models it seems that the 2nd model performs better, furthermore the distance travelled but the operators in the non pick off model seems lower with higher throughput. Is there something I'm missing. I would have expected the opposite results. @Felix Möhlmann

With Pick off.fsm Mech Accumulation without pick off.fsm

Software Version:

FlexSim 21.2.4

pick off comparison

with-pick-off.fsm (148.4 KiB)

mech-accumulation-without-pick-off.fsm (123.6 KiB)

Answer 1 · 2022-12-01T08:08:17Z

Felix Möhlmann answered Dec 1, '22

In the model without pick offs, the operators are pulling the items (via Process Flow), ordered by distance, so they will always choose the item closest to them.

In the model with pick offs, the transport tasks are distributed by a dispatcher in FIFO order. So essentially, the items are "pulling" an operator to move them. While the closest operator is chosen, there might still be other items closer to that operator which should be picked first to avoid unnecessary travel.

So to make the models comparable, I would suggest you use the same task distribution logic in the model without pick offs: Items are pushed to a list by the pick off queues and then pulled by tokens representing the operators. Since the items are not moving, you can use the default "distance" field in the list and simplify the Process Flow since the calculation to predict the pick up location is not needed anymore.

with-pick-off-list.fsm

with-pick-off-list.fsm (147.2 KiB)

Answer 2 · 2022-12-01T14:40:21Z

Adil M answered Dec 1, '22

That makes sense! Thank you.

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Model comparison with pick off vs without pick off

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