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Chris.J

FIFO Explination?

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The project consist of loading 7 separate products into boxes with the load counts of each updated in a database daily. Each box will be labeled with a barcode. Boxes travel down a conveyor that has 7 stations where products are loaded from feeders. We’re scanning the box at the first station, and selecting corresponding barcode and inserting load counts into tags on the PAC 3000. This is where things become fuzzy. How should I track load counts from station to station? I was planning on using arrays for each station and having the counts shift through the array. I am new to Programing and having a difficult time figuring out what is the best method of attempting this. Should I use FIFO? If so, can someone explain how to use it or better yet share and example. I have read the help for the FIFO instruction but have had a hard time understanding how it works. Any and all feedback is greatly appreciated! Happy to elaborate if anything is unclear. Thanks, Chris Edited by Chris.J

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i would start by getting better description of the process. that would allow making easier choices when selecting important things like control strategy, tracking etc. for example is each box making stop at each of the seven stations? do all boxes get some quantity of each of 7 products or one box gets only number of products from one station? how is indexing done? are there stoppers at each station or conveyor is divided into sections? there is a difference between indexing all stations at once and asynchronous indexing. the less you know about process, the more flexible system you need to use. if i understand correctly: 1. process starts at station number 1 where scanning takes place. 2. each station dispenses different product 3. based on scan (recipe) box can receive certain number of products at any station. what i would do is create an array of sufficient length for each station (and include some spares too). for example single array could be say 10-20 byte (or integers, if byte is too small). for example elements could be: 0 - optional ID or recipe index (barcode) 1 - required qty for product1 2 - required qty for product2 3 - required qty for product3 ... 7 - required qty for product7 8..10 spares 11 - actually dispensed qty for product1 12 - actually dispensed qty for product2 ... 17 - actually dispensed qty for product7 18..20 spares alternatively one could cut them dows and only have 7 elements where elements 0..6 contain quantity of each product (if minimalistic/efficient memory use is required). you can set required quantities as negative values for example, then at station that dispenses product1, increment correcponding array element until it is at zero. at the end of line all boxes should have all ellements at zero. any element negative, means box is short of that product by that quantity. any value positive - there is too much of some product. idea is to create such array for each station and as the box moves from stn0 into stn1, just copy content of array stn0_scan into array stn1_prod1 (record moves with box). no FIFO needed. keeping things in several arrays rather than one long one is more flexible because: - you can any time add another station (you just create anoter array) - you can increase size of arrays without having to rename any of existing variables - you can support any type of indexing (cannot do that with FIFO operating on single queue)

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