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Old April 25th, 2013, 09:17 PM   #9
United States

dalem is offline
Join Date: Sep 2005
Location: NE Wisconsin
Posts: 101
Well, here goes. This will either clarify or confuse the task at hand.

By the way, I have another FIFO/data table in this program I'm not currently using. I'm going to borrow it next week and throw in a quick COP scheme as stated above. I think it will work just fine and I can compare along side the 4 existing individual FIFOs. Main goal here is to get rid of 4 and replace with the one single data file, combining that which is now in those 4. The program is doing nothing with the control file bits so I see no need to stick with the FFL/FFU.

As for those discharge points down stream, that's something down the road, so we don't need to consider much on that now. As long as the data table takes care of the parts entering, it will no problem sorting it out to the new exits. At that time, the values I move into the entry points will be coded some way for varied actions at exits.

As for details on this conveyor, it is an over head power and free conveyor. This particular conveyor/drive is roughly 300' long. We have 18 drives throughout the plant some consideraly larger others smaller.

Parts we make get hung on these load bars which are 25' long each. Each of those load bars have a set of trolleys on each end and are either staged in various tandem load and unload cells and are released into these single transport lines. The area I'm redoing is the transport line these carriers/load bars have to merge into and be tracked all the way down to the end. (sometimes, I'll explain later.)

As stated, the entry points are aprox 28' apart with the last 2 (furthest up stream) being 40'. The load lanes, 7 total are tandem lines. Once the carriers are loaded, the operator press a release button, their stop gate opens and the carrier moves up to another stop just before the transport line.

These carriers then sit there until the section in the transport line is clear. When clear, gate opens, carrier drops out. There is a counter that's reset and that needs to count to some value before the PLC thinks that carrier (load bar) is out of the way.

As for carriers coming from up stream, as carriers come along down this line, they hit a limit switch just before each up coming entry point. That resets another counter to zero and that counter needs to count up to some value so that the lane it's passing thinks/know that carrier is past and the exit point is clear again. This is the physical carrier detection which works when the loads hung are <25' long.

On 4 of these entry points (was originally 2, I added 2 more), we regularly hang parts which are up to 40' long. This is where the tracking FIFOs come in. When one of these long carriers enter the transport line, the string of 333,333,333 or 444,444,444, etc move along down the line with the carrier and in a sense compensates for the additional 7.5' of product overhang off each end of the load bars. (The 3's and 4's only represent which load cell the carrier came from. Many 333s or 444s used (I think) just to make it look like one long carrier moving down the through the data file. Value bein gmoved in these data files can be any thing but 0 (zero). Each entery does not consider 0s as being a carrier in the way and prevent another carrier from merging in.

Other areas (drives) in the system also use FFL/FFU to deliver carriers to multiple powder coating booths, unload lanes, etc. Most do not use the control file bits/values but particular FIFOs do use 4 do the control POS value.

FYI, I've been programming, tweaking, optimizing on this system since 98. The project above it to redo the whole traffic control coming out of these load cells and get more load out per hour. As it is, it's not uncommon to loose 1/4. carrier here, 1/2 carrier there, with wasted spaces, not large enough to merge into. I have other plans with other parts of the merging scheme but need to fine tune these LONG loads first.

Hope this helps and thanks again for any suggestions.

Thanks again,


Last edited by dalem; April 25th, 2013 at 09:27 PM.
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