Pallet buffer positions: stop exactly in the middle of a conveyor before a split

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Kaspar Chabot asked Sep 30, '16 Sam Stubbs commented Oct 19, '16

Pallet buffer positions: stop exactly in the middle of a conveyor before a split

Hello

The system I am trying to model is using a sideways transfer type from a roller conveyor to a chain conveyor (the opposite of this Youtube movie conveyors). The whole conveyor is set up to be a buffer, with photo eyes stopping pallets at certain fixed positions on the belt system (usually one belt contains just one position).

For merging pallets onto one line I could manage to set up some scripts that made it work. For splitting I have some more problems (see attached files).

I want the transfer position itself to function as a buffer position. When trying to model this in Flexsim using Decision Points, I bumped into the problem that sending the item from one decision point to another decision point apparently needs to happen before the x location of the decision point and half of the item size (in case of a center item-edged DP) line up with the sideways transfer.

If the x location of DP3 is too far to the right (in the split model included), all items will continue straight down the line.

Is there any way to solve this?

Thanks!

test-palletposities-split.fsm

test-palletposities-merge.fsm

Software Version:

FlexSim 16.2.0

conveyor decision point split send item dp

test-palletposities-split.fsm (26.1 KiB)

test-palletposities-merge.fsm (28.1 KiB)

· 2

Kaspar Chabot commented · Oct 03, 2016 at 07:14 AM

The issue is that I want the position for the box to stop to be exactly in the middle of conveyor C3, not before that, and then make the decision to send it to the upper conveyor (C5). This allows a correct simulation of the type of 'sideways transfer with fixed pallet positions' system that I'm trying to model.

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Kaspar Chabot commented · Oct 03, 2016 at 08:29 AM

I found a fix myself with the use of photo-eyes for the stopping logic and decision points for the destination logic. It should also work just with decision points if you add separate decision points for the sending logic, but photo-eyes look different so it is easier to visualize the separate logic. I will try to post the solution here after I fix another issue in the model with blocking the item in the center if there is an downstream item on the next position, regardless of its destination (left or straight). EDIT: Solution added as attachment

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test-palletposities-final.fsm (28.1 KiB)

Answer 1 · 2016-09-30T17:42:49Z

Sam Stubbs answered Sep 30, '16 Sam Stubbs commented Oct 19, '16

If I'm understanding what your issue is, I think you can resolve the splitting issue by setting the decision point's "Item Edge" setting, to leading edge, instead of center.

I've reattached your model below.

2757-test-palletposities-split.fsm

leadingedge.png (15.1 KiB)

2757-test-palletposities-split.fsm (25.5 KiB)

· 4

Kaspar Chabot commented · Oct 03, 2016 at 07:18 AM

I tried using leading edge before, but still it doesn't work to align the box exactly with the sideways transfer like I want it to.

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Sam Stubbs ♦ Kaspar Chabot commented · Oct 18, 2016 at 08:33 PM

You have to "wiggle" the point so it snaps to the edge of the conveyor in the right place. My attached model should show the point in the right place.

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Kaspar Chabot Sam Stubbs ♦ commented · Oct 19, 2016 at 07:19 AM

@Sam Stubbs It worked until I had to use the decision point both as a split and a merge. At a crossroads the flow can split up (forward or left) or be joined from the right. I fixed this by making the 'send to destination' decision before the crossroads alltogether - this seems to have a large influence on how the item behaves - and then having the decision point to stop the item 1 mm before the center of the crossroads. This will fix the splitting problem. For the item joining the conveyor from the right, I made it move slightly to the left (2 mm) so the center of it would touch the decision point on arrival and it could stop when required. I included a small model to show how I solved my problem. The logic in the center isn't ideal because it would take me too much time to do it properly, but it shows how not to have items bump into eachother when solving this kind of problem. It also works perfectly with larger flowitems.test-conveyor-split-merge.fsm

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test-conveyor-split-merge.fsm (29.2 KiB)

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