Odd issue with photo eye/decision point to reject item

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Steve McDonald asked Feb 8, '17 Sam Stubbs commented Apr 12, '17

Odd issue with photo eye/decision point to reject item

I have an issue where I want to reject two items on a conveyor that are stuck together. I am creating extra items and randomly inserting them onto the conveyors and allowing 2 items to overlap simulating being stuck together. I am using a photo eye and have the block time set to allow a single item to pass, but two items will block the eye due to taking to long to clear. I have decision points on each conveyor good (green) and reject (red). Of my two parallel lines, the right side seems to work fine, but the left side sends an item into space instead of side transferring to the next conveyor after the photo eye is blocked.

The decision points do not always seem to work as far as sending the item to the correct conveyor. I also tried rejecting based on item type passing a decision point instead of a photo eye (type 1- ok, and type 2 - reject) and creating a small percent of item type = 2 to reject and didn't always get a successful reject. Is there any rule of thumbs as far as where the decision points have to be placed or a min distance from entry/exit points. Or if the conveyors are not joined, and using connectors can that cause an issue

Thanks.

Steve

Software Version:

FlexSim 17.0.2

decision points

mergedecisiontest.fsm (29.8 KiB)

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Sam Stubbs ♦ commented · Feb 08, 2017 at 04:49 PM

I'm looking at your model, and it looks like if you slow the model down considerably, that the redirect does work, but it's only working on the first item not on both overlapping items. It also looks like you may have uncovered a bug with your conveyors. Sometimes it seems like items run off the conveyor and "float" on forever.

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Steve McDonald commented · Feb 09, 2017 at 05:03 PM

So, my entry transfers on the conveyors I was deciding between had the "Max Transports in Transit" set to "0", and was causing the items to pause or stall at the exit. My conveyors were not joined as they are at different elevations and the decision points were sending items to those entry transfers.

As far as the item floating off the conveyor, not sure what caused it exactly, but went back and confirmed all conveyor locations and elevations as there may have been a slight mismatch when joined (less than a half an inch), but it has been eliminated.

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Answer 1 · 2017-02-08T18:28:32Z

Sam Stubbs answered Feb 8, '17

Looking into your model, with the current issues, I thought that maybe I could recommend a different approach to the model. Here is an example using Process Flow and a little bit of custom code that tackles the same situation, but bypasses some of the other errors and issues you ran into.

rejectconveyor.fsm

rejectconveyor.fsm (23.4 KiB)

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