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brisutterfield

Conveyor flow logic

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Does anyone have any code for a 3 to 1 conveyor merge? Attached is a file of the layout of the conveyors. The existing code is to long and and causes boxes to crash at the merge frequently. I am trying to have one line release for 15 seconds. Then stop releasing and wait 3 seconds so the boxes can clear the merge, then have the next line release for 15 seconds. This process would repeat for the third line also. If one or two of the lines do not have any cases on them they should be skipped in the release cycle. We are using AB PLC5 w/RSLogix 5. Input are from 3 photo eyes. Outputs are to 4 motor starters.

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Having lived with warehouse conveying for a couple of years on a previous job I can tell you that a "simple" 2 to 1 or 3 to 1 merge is anything but simple. I'll see if I can dig up some of my old code examples. If you've never written one from scratch I'd encourage you to try. It is not as easy as it sounds. Especially when you want to skip lanes.

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Bob is right, it starts out as one of those "all you gotta do is..." tasks. There are a lot of variables to play with. Then give the lanes different priorites. Or after a lane times out for lack of product, use the timeout value as part of the clear out timer for the next lane. I can get my hands on a pretty fancy 3 to 1 program, but not until Friday. To be honest, they are fairly hard to follow if you didn't write it. Mine makes perfect sense to me, but my boss hates it.

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I am trying to figure out the existing code which is 241 rungs, just for this merge. The existing logic consists of: Training logic, release timers, no carton present timers, merge sequencers, pre-release enable logic, pre-release calculations, merge clear calculations, hiccup fixes, merge run enable logic, package present latch, last box delay stop and a few other things. There is alot that goes into a simple 3:1 merge.

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Last year we upgraded a 200 tray conveyor with 6 belt driven feed conveyors. The trays would run at 155 F.P.M. We used photo-eyes to check for a empty tray before each loading conveyor. Each loading conveyor would run independent of each other. Each loading conveyor would use the one photo eye before it's loading point. We then would track the bundle to 13 user selected dump stations. The system was built on a Control Logix plateform. The extra photo eyes made life a lot easier. thanks, drusso

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USER BEWARE. This is a very simple 3 to 1 merge. You will have to adjust the addresses for your process. It also does not have mtor overload and fail to start logic. it is bare bones. 3_1_MERGE.zip

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A photo-eye at the merge point to detect that a released box cleared the merge point would allow ome control reliability.

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"The existing logic consists of: Training logic" Is this logic to train the merge how long the run-out timers should be for each lane to clear out the last box released? If you are going to the effort to re-write the logic to solve merge issues, I would also add two photoeyes to act as jam detecs at the merge points on the second two conv's. This makes your runout timers more accurate and any jams you do have, less of a pile up. It currently looks like you don't have any jam detect PE's. Which surprises me if they were serious enough to write 241 rungs of code. Edited by Charlie Maher

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The PE at the discharge end of each of the three lines is used as a package present PE and to detect jams. The PE should see a gap between each case as it goes by. If the conveyor is running and no gap seen for three seconds the line shuts down. There is also a long range PE running down the length of the Merge to detect jams and for personal safety protection.

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Thank for the code. I have no way to look at it untill I get back to work on Monday though. I'll check it out then. Thanks again.

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