What's the funniest joke you've ever heard about your industry or type of business?

Actually that is starting to get some attention...

It is now called "Predictive Maintenance Logic".


I would bet if you programmed a HMI to display a Change The Left Upper Bearing every couple of years the managers would be amazed at the insight and knowledge of the programmer. Then if something unannounced does fail just write it off to a premature failure.
 
Even funnier is when you hear that the program of the said machine must be changed.

I have had exactly that discussion with a client shortly before Christmas indeed. Client was 100% sure that it was a software issue. The cause of the problem turned out to be mechanical, as I had stated from the get go. Similar thing has happened to me several times before. It would be funny if it wasn't so sad.

A couple of years back, I heard from a colleague from where I used to work about a PLC that we had programmed in the late 80's. The program hadn't changed in all those years but it took them almost thirty years to hit the right (wrong?) combo of switches to uncover a bug in the programming. I would have wagered a tidy sum that software was the last thing to suspect in a system that had worked daily for decades without an issue.
 
A couple of years back, I heard from a colleague from where I used to work about a PLC that we had programmed in the late 80's. The program hadn't changed in all those years but it took them almost thirty years to hit the right (wrong?) combo of switches to uncover a bug in the programming. I would have wagered a tidy sum that software was the last thing to suspect in a system that had worked daily for decades without an issue.

Had a similar issue but not decades long but anyway, programmed a gantry that fed an index table. There were interlocks that prevented the devices from crashing into each other. I wrote them as gantry positions that would let the index table move and an index in position that let the gantry move. After the initial startup, the customer flipped the the orientation of the part coming into the machine which resulted in the gantry being in a different position to pickup a new part.

For the most part the gantry and index table got along but about twice a day they would lock each other out for no apparent reason. I'd sit there for hours and nothing would happen then I'd go back to the shop and get a call from the customer that it was locked up. I really felt stupid when I figured out that I hadn't adjusted the interlock points when the part orientation change came through.
 
I had a similar one about 5 months ago
I have a long time client that has a pair of spring machines with SLC 150 PLC they have both been running without any problems since before is have known them ad that well over 15 years.
So I never had a reason to even look at the programs or do a back up. We have talked about upgrading
them both in the upcoming year, not a priority by any means. They have other issues in the plant to deal with first. The material 3/8 to 1/2 in spring steel wire.
As very simple program advance he feed to a preset length. The length is set in an external counter the counter just triggers an input to stop the feed and cut the wire. The cut is completed with a hydraulic sheer. Advance for 5 sec and retract for 5 sec. Reset the counter and feed the next spring and repeat.
When I got the call the shear would only advance a little and retract without cutting the wire. And continue to feed the next spring making a real mess.
Getting into the program is a challenge itself because the software for them will only run in DOS and doesn’t play well in windows.
When I finely did get in the program it was running just as it was programmed no errors. But what I did discover was the cut advance and retract timers preset was .5 sec way too short to complete the cut.

Now on the SLC 150 you set the time base for the timer when you program the timer it cannot be changed after that. To change the time base you have to delete the timer and reprogram it using the new time base the preset for the timers and counters is only 3 digits 999 is max. The time base for .5 would be .sec would be .1 and the time base for 5 sec would be 1 selectable so for .5 sec time delay you would program the timer with a .1 time base with a preset of 5 and for a 5 sec delay you would program the timer with a time base of 1 with the same preset of 5.
What I found that the time base for both was .1 with a preset or just 5.
I just adjusted the preset on both to 50 and everything worked as it should and still is.
The only thing I can figure is for some reason the time base on both timers shifted.
I know nobody I the plant has the software or the cable to connect to change anything nor would they have any idea how to use it if they had.
I don’t know if other timers in the program shifted the time base as well or not, the way they were used it would not make a difference with the time base.
I recommended that they accelerate the upgrade because the processor may be on it’s last legs but as with everything is not a priority until in brakes down, then they need to today.
 
I had a situation that in all likelihood should have been exactly the same, but for an enormous fluke...

Basically, this system has three modes. In normal running, it would switch from mode A to mode B and back again maybe a couple of times a day, and from mode B to mode C and back again very rarely. Probably around once a month, if that. This issue would only ever arise if the system switched from mode C to mode B within 15 seconds of 10am, and since that mode change was a "once-a-month, if that" type of mode change, you'd imagine that it'd probably take years for it to fluke a 10am changeover.

Until, about a week after I left site having commissioned the system, someone manually switched modes because they wanted to take a screenshot of the SCADA in the other mode for the user manual, and then switched it back - at 5 seconds past 10am. Could not believe that they managed to catch it, but I was sure glad they did before it went into full blown production mode!
 
Or the timed bug I discovered in a large conveyor system I did.
They told me it goes nuts (their words) every now and again.
Usually around lunchtime.

I went down at that time and sure enough, lots of strange things happened
then it settled down.

The outside workers came in for their lunch all wearing Hi Viz jackets and as they walked across the floor they triggered lots of photo cells with the reflecting strips on their jackets.
 
I got called back to a machine with a conveyor that had been running for years and suddenly went haywire.


The conveyor start and position were controlled by photoeyes and worked fine until the shop replaced all the sodium vapor high bay lights with LED lights. The spectrum of the LEDs triggered the photoeyes. I had to install non-optical proxy's.
 
A priest, a doctor, and an engineer were waiting one morning for a particularly slow group of golfers. The engineer fumed, "What's with those guys? We must have been waiting for fifteen minutes!"

The doctor chimed in, "I don't know, but I've never seen such inept golf!"

The priest said, "Here comes the green-keeper. Let's have a word with him."

He said, "Hello George, what's wrong with that group ahead of us? They're rather slow, aren't they?"

The green-keeper replied, "Oh, yes. That's a group of blind firemen. They lost their sight saving our clubhouse from a fire last year, so we always let them play for free anytime."

The group fell silent for a moment.

The priest said, "That's so sad. I think I will say a special prayer for them tonight."

The doctor said, "Good idea. I'm going to contact my ophthalmologist colleague and see if there's anything he can do for them."

The engineer said, "Why can't they play at night?"
 
This one isn't really an engineering joke, but it cracks me up:

An infinite number of mathematicians walk into a bar. The first orders a beer. The second orders half a beer. The third orders a quarter of a beer. Before the next one can order, the bartender says, "Hold on guys, two's the limit!".
 
And one more...

A mathematician and an engineer are called in for a psychological experiment. They're sat down in two chairs at the end of this incredibly long room. At the end, a door opens and a naked woman steps out. The mathematician and engineer squint, and even then can just barely see her.

An intercom on the wall announces, "at the sound of the bell, you may move your chair half the distance between you and the naked lady."

So the bell rings, and the engineer scootches halfway down the entire hallway (mime out scootching here for added laughs when telling the joke). However, the mathematician doesn't move.

Again, the bell rings and the engineer scootches halfway between him and the woman, but the mathematician doesn't move.

The experiment is stopped and one of the scientists behind the experiment says to the mathematician, "the instructions were clear! Why didn't you move?" The mathematician replies, "I'm not an idiot. Obviously if we only move half the distance, we'll never get to the naked woman."

So the scientist says to the Engineer, "Well if that's true, why did you move?" The engineer replies, "Well, I knew that, but I figure I'll get close enough for practical purposes."
 

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