I was tasked by a conveyor company out of Tampa, Fla., to investigate whether a parts-delivery system's throughput could be improved beyond the specified four totes per minute. Information about the system was sketchy at best, but with some home-brewed adapters to the I/O, I was able to determine what the position indicators, laser scanners, pickers (a small elevator), and RS232 command station were doing.
I created my own I/O using some devices provided by a US manufacturer and adapted them to an Everex step 32 computer system. I used QBasic's compiler basic to generate the bulk of the structure with some assembly to handle the laser scanners interrupts.
The delivery system consisted of a 432 tote (two foot x two foot plastic bucket) divided into six layers of 72 totes each and two small elevators, one on each end of a long loop of approximately 60 feet. The picker's job was to receive a tote extracted by a pneumatic piston or insert a tote via a set of belts aided by a paw that helped push the tote on to the chain-linked tray. Each pair of 72-tote layers was controlled by a separate embedded computer. Another computer handled the pickers, and another computer handled the RS232 communications between the delivery system and the host... five computers in all.
The problem was the brute force approach used to drive the now-disconnected I/O system. Each command from the host had to be parsed, and the pickers had to be directed to either go to a certain level and pick up a tote and deliver it to a conveyor level or vice versa. The first cut was to divide and conquer, so all of the extraction commands were divided from the insertion commands. That provided a reasonable outlook as to what the true nature of the requirements of movement were.
From there, I was able to create one single movement and used it twice regardless of the type of command received -- it was "move the picker, move the tote." Now, simply by providing a target for the picker, the routine knew where to move the picker. From that point, if the target was a conveyor, the software would move the picker to the conveyor level and generate the signals needed to drop the "K" stop to pick up the tote and center it on the picker. The second pass parsed from the host command was the delivery of the tote. In this particular example, the software would direct the picker to a storage layer and insert the tote.
This is, of course, very simplified, as there was a layer movement (using a shortest-route algorithm) to get the proper tote number to the correct end for the picker, locking the layer and either executing an extraction or insertion.
All in all, the system was now capable of delivering nine-plus totes per minute, instead of the manufacturer's four. The story doesn't end there, however! Because of the increased delivery speed, the host system had to pace the requests, because the totes would jam the exit conveyors, causing them to buckle and leap off the conveyor!
This entry was submitted by Rick MacLean and edited by Rob Spiegel.
Rick MacLean is a design consultant now working with a motion product company located in Longwood, Fla.
Tell us your experience in solving a knotty engineering problem. Send stories to Rob Spiegel for Sherlock Ohms.
I agree with Nancy and the comments about all of the junk that microsoft has dumped on us over the years. PLUS, they never release an operating system that is not buggy any more, if they ever did. And all sorts of things work the way that programmers think, and programmers are NOT NORMAL PEOPLE. We all know that, most are too polite to say it, though. What was so hard about launching a program by calling it's name? And using a file for more than one program is something that I was doing back with DOS 3.???, and it worked quite well. Plus, the programs were written efficiently and they were fairly small, and the operating system was just a tool to use with things, it did not have it's own 40 foot tall ego, like most versions of window do today.
The intensely bloated software is the reason that the 50 MHz computer is not fast enough any more. We really don't need all of the stinking little features that we always get, and there is really no reason that a person to lazy, or to dumb to learn how, should be using a computer.
Now the OS is tending toward controlling what we do and how we do it, and attempting to say that the only right way is the windows way. I see problems with that, it sounds a lot like thought police to me. Shades of "1984" (the book, not the year).
Problem here is being the guy stuck in the middle. The ultimate reason for the log jam is two-fold. They couldn't speed up the conveyor that took away the totes plus the Navy or original conveyor manufacturer never planned on the delivery being that fast.
Result was that the host computer that handled all of the parts ordering had to be throttled down so that they didn't request any more than the conveyor could handle!!
Nancy: I have access to two PCs, both loaded w/ WINDOWS XP (SP3). For the most part they work very reliably, and I've become very familiar w/ some of the "behind the scenes" options, etc. A couple of years ago, I bought an H-P laptop w/ WINDOWS 7 for exclusive use of storing & editing my digital images. From day one, I became VERY frustrated. For one thing, OUTLOOK EXPRESS was gone!.... replaced by WINDOWS LIVE MAIL. It didn't look or act like OUTLOOK EXPRESS. Creating storage folders, etc. was vastly different. The whole operation of the software was cumbersome. That aside, while working on an application (PHOTOSHOP, etal), the screen went totally dark. No one could determine the cause, and H-P wasn't interested either. In total disgust, I contacted a fellow who provides support & hardware. I TRADED the H-P for an ACER FERRARI laptop w/ WINDOWS XP PRO. The screen is excellent; the PC works fine, and I can buzz through my tasks with ease & CONFIDENCE!
It IS unconscionable to me that AFTER almost THIRTY years of WINDOWS, MICROSOFT still distributes a decidely FAULTY product, and NO ONE has provided an acceptable alternate to date! The closest anyone ever came was when I-B-M offered OS2!
TOOL_MKAER: I enjoyed reading your technical description of a screw. While you ARE absolutely correct in that description, I think it is taking my comment to extreme. I don't believe that the noun "screw" is jargon anymore. The physical item has been with us for too long. It deserves its place with all the other legitimate nouns in the dictionary. However, that does not change my opinion of so many of these posts wherein the author gets so tangential in their description that it takes a dictionary to determine what's being described.
Those days are gone for most electronic products. Consumers don't think in terms of repair, they think in terms of replacement. New features win the audience, so after just a couple years, the idea of repairing consumer electronics becomes out of the question. I would guess that most of those buying the iPhone 5 are replacing an iPhone that already works fine.
There are occasions when the fastest speed is not the optimum speed. In the process described, the slowest step in the sequence should have been the first addressed. Your example of horse power was a good one. I had a friend who dropped a big engine in an old Ford. All the increased power did for hole shots was overcome a rear end not designed for that much torque and it would spin the splines off of the axel. Once the vehicle was rolling it was a different story, but there was never a time the vehicle was able to fully utilize the increased horsepower. Perhaps this conveyer system will never be able to fully use the increased speed.
I miss the days where you could just tear into something to fix it - just swap out a cap that had fried and brag to your friends LOL. I do feel sorry for the youngsters today - they board swap instead of having the fun of troubleshooting...
Nancy, I think what we're seeing is another example of disposable consumer electronics. Consumers don't fix computers, TVs or phones. They throw them away and get new ones. Consumer electronics go obsolete quickly.
Ain't that the truth, Rob! That goes for PC HW too! I remember being in Comp USA a few years ago (well, maybe more than a few LOL) looking for a motherboard. I was so aggravated to find out all the ports were integrated onto the board instead of the old days where we could buy what we wanted and drop it into a slot. Back in the day - card go bad - take a shot at fixing the old one and if not - just replace it with a new one...Want to upgrade your video card - swap it out...I just could not believe anyone would integrate everything directly onto the motherboard!
I agree with your comments about jargon, but sometimes the only language one knows to relate the issue is jargon. For example: If someone wants to describe the phenomonae of moving things in a linear attitude with circular motion he can describe an inclined plane wrapped around a cylinder, or he can say a screw. The first in technically correct while the second is jargon that has worked its way into our mainstream language.
Those that know the jargon get the solution and those, me for example, who do not know are clueless about both problem and solution, but enjoy reading about the engineer's effort to correct.
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