General Automation Discussion

[twohowlingdogs]

I have a rather tough issue to automate and thought all my friends out there could help give ideas on how to do this or possible solutions.

I am automating a spinach warehouse. I have one line of empty cartons that feeds 8 filling stations. When a filling station needs a carton, I have a bit set saying so which triggers the stopper to pop up, when a carton gets in place, I push the carton down the line for the filler and waits until it needs another one. Easy huh? Well that part was! The difficult part is I don't want a couple stations to get all the cartons so I need to figure out how to force the 8 stations to take turns yet I also don't want one station to starve because another station is going slower for one reason or another. (I can set an Enable/Disable bit if we aren't using the line.) 

In all reality, I can have all of them asking for a carton at the same time. So I give one station a carton and by the time I get to say, the fourth station, the first one could want one again and with logic read like it is, the first one could get another carton before the fifth line gets one.

I hope you are following my problem here. I've considered using an INT and having one bit in the int for each line and once all the bits have been set for active lines, then the first line can have another carton by resetting the INT to 0. But that could be difficult to follow since a line could be disabled thus making this INT a different value. That's a lot of options!

Anyway, if you have an idea or have done something like this, I'll take in any ideas out there. Thanks in advance!

Paul

[Flames]

Hello,

i would do some kind of logic base on first in, first out you have to deserve every station in order if not, one of the filler line will stop by missing cartons. I create a flag associate with a number on every station, raise the flag when missing cartons and log in order that flag to deliver the box. You should be out of toruble with something like that.

[gardens]

Look at the process time of each filling station it should be long enough to allow other following station get a carton. If not then the rate at which this plant can process exceeds what you can supply from a serial carton filling line.

The solution may need a step back and take a holistic view of what the process is trying to achieve, which I gather is process rate.

There may be a solution by feeding empty cartons from each end of the empty carton line, and concentrate on keeping the high process rates at each entry point of the empty cartons line.

Another view would be to look at not feeding empty carton serially but in parallel, I mean that if a rack of 8 empty cartoons can be maintained above the 8 stations and dropped in when required then the empty carton control become a simply matter of keeping empty cartons available to be dropped when required by each processing line.

I am trying to say that the processing rate is dependent on the serial fashion of the supply of empty cartons.

Change from serial supply to parallel supply and each process station can process at max rate.

I feel any solution you implement will cause a reduced process rate because a station will need to be stopped outputting while a carton is delivered to a station wanting one.

This wait will reduce processing rate.

[Stikstof]

Hi Paul,

I don't know if you still have an issue with this, but at my job we have a case former that supplies 3 case packers.  Here is how we do it. 

- The belt that supplies the case packers runs continuously.   The belt has a smooth surface so boxes can slide over is when a stopper is up. By default all stoppers are up.

- At case packer 1 the stopper is up and we have 3 cases waiting.

- If case packer 2 needs boxes, the stopper at 1 goes down, and the 3 boxes are moved from 1 to 2.

- If case packer 3 needs boxes, the stopper at 1 and 2 goes down, and boxes are moved from 2 to 3 and from 1 to 2.

- If a case packer needs a box, the pusher pushes one box in the case packer.

If you need to supply 8 case packers I would increase the size of the buffer to 4 or 5 boxes if possible.

[Vong]

You could create a DINT for each filler. When the filler gets a carton, it adds one to the DINT. Give priority to the cartoners with  the lowest number. If the cartoner is disabled, you can ignore that one, and when it comes back online, take an average of the running cartoners and push it into its DINT.

When the line goes down, you could zero them all.

[laundry]

Hi Paul,  I don't know if you still have a problem?  I had a similar problem with the plant I am in.  I have 5 - 200 pound dryers that are feed with one automated shuttle.  I want to keep the number count as close as possible for each dryer with out a loss in production.  I set up a shift reg. that is loaded after the dry is empty, as on one can empty at a time.  (the dry times vary between 3 min and 20 min).  the order that each dry is loaded depends upon the order that each dryer becomes available or is unloaded.  the faster the dry time the more often that dryer is loaded.   this seams to keep the number count close for each dryer while at the same time no loss in production.

I hope this might help.