Picking up boxes from a rack

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David Dorantes asked May 17, '17 Trex commented Aug 23, '17

Picking up boxes from a rack

Hello.

I am doing a Simulation in a Warehouse, I have 15 racks and there are 5 resourses picking up the boxes from the Racks, but when the transporter goes to pick up a box, it travel to the center of the Rack and then goes to the Bay and Level to pick it up.

I configure the forklift to "Travel offsets for load/unload tasks" because i want to simulate how the forklift travel to the specific location where its located the boxes (Bay and level).

But for example, when the Transporter have to pick up 4 boxes from Rack 1 Bay 5, it travel to the center of the rack and then goes to the bay 5, pick up only 1 box and then travel to the center of the rack, come back to the bay 5 to pick up one more box, then come back to the center of the rack, etc.

How can i do to the transporter stays in the same bay until pick up all the boxes in that rack??

rack

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Matt Long commented · May 17, 2017 at 10:22 PM

You'll have to share your model because it works correctly when I build a simple model with a rack and transporter. The transporter never moves to the center of the rack and picks up all of the items in the bay before moving. See my sample model:

racktest.fsm

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racktest.fsm (22.6 KiB)

David Dorantes Matt Long commented · May 18, 2017 at 03:26 AM

Can you share your sample model in version 17.0 please? i haven't been able to update the last version because of administrator permission.

I share you my model.warehouse.fsm Thanks.

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warehouse.fsm (1.7 MiB)

Sam Stubbs ♦ David Dorantes commented · May 18, 2017 at 02:29 PM

You should still be able to view his model if you download the express version of 17.1. In the future it is helpful to us if you can indicate which version of the software you are using by selecting your FlexSim version in the drop down field in the Ask a Question. That way we don't have to assume what version of the software you are using.

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David Dorantes Matt Long commented · May 18, 2017 at 05:21 PM

Hello. I am seeing your model and it function correctly, but i forget to say you that the Racks are connected to a Combiner/transporter instead to a Queue. So, the combiner has 15 connections (15 racks) and the Transporter moves the combiner to the racks to pick up the boxes, but the Transporter always travel to an specific place of the rack and not to the correct bay.

Is there a way to do it??

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Matt Long David Dorantes commented · May 18, 2017 at 06:08 PM

You're going to need to send your model if we're going to see exactly what's going on and how to correct it.

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Answer 1 · 2017-05-18T20:19:34Z

Matt Long answered May 18, '17 Matt Long commented May 22, '17

The issue comes from the AStar Navigator. When you give a travel task to a TE that is attached to the AStar, it travels to the center of the object. Since a standard task sequence for moving a flowitem includes a Travel task, the transporter always moves back to the center of the object. (This is something the development team is currently looking at changing.)

In order to work around AStar's standard logic, I replaced all of your Rack's Use Transport field with Process Flow: Use Task Sequence Sub Flow. I then created a Sub Flow that builds the task sequence for each item being moved from a rack. This gives you the ability to make decisions about how to travel at the time of execution (as opposed to when the task sequence was created).

I created a label on each Transporter called TravelToRack that is set to 0 when the transporter has not yet traveled to the rack, and 1 when it has. This allows me to only call the initial travel task once. I also use a Travel to Loc task instead of a Travel task so that instead of moving to the center of the rack, I move to the end of the rack. The rest of the activities build the standard task sequence and then reset the TravelToRack label on the transporter.

Hopefully this helps. If the logic I put into the Sub Flow is not quite right for your model, you can easily change it.

warehouse-correccion-updated.fsm

warehouse-correccion-updated.fsm (1.7 MiB)

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David Dorantes commented · May 19, 2017 at 01:25 PM

Hello Matt, thanks for your support. I think that model functions better, but i don't know why the TE traverses the racks in some cases.

Also, i would like to know how to use the function "Process Flow". Do you have any information about that?

Thanks, regards.

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Matt Long David Dorantes commented · May 22, 2017 at 03:50 PM

There's a ton of information and tutorials in the User Manual on Process Flow. I'd start there.

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David Dorantes commented · May 19, 2017 at 01:49 PM

This often happens, the TE picks up all the boxes needed and then travels to the end of the rack and lifts up the load, then travel to pick up the next delivery (pallet). I would like you to travel for the next delivery when you pick up all the boxes.

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wharehouse-correccion.png (1.1 MiB)

Matt Long David Dorantes commented · May 22, 2017 at 04:10 PM

I just noticed your Forklifts have Combiners inside of them. This is likely the cause of some of your issues. You should not put FR's or other TE's into a TE. Since you've got Process Flow, you can very easily do what the Combiner is doing without writing a bunch of code. You just need some Move Object activities to move the loaded boxes onto the Pallet. The Pallet already has logic for places the boxes in the correct locations.

Try removing the Combiners and see if that removes the odd behavior.

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