machine superstition

[unsaint33]

Its a silly question but I wonder if anyone else experience this... Our plants make thermostat devices, almost all of its parts made in house so we have a lot of different machines, new and old. Here is the strange part... More often than not, when I get service calls, within a span of 2 or 3 days, the nature of the problems tend to be very similar. Yesterday and today, I got four service calls, all for different machines; a metal-cutting saw, grinder, roll metal dispenser, stamping machine. All of them had a bad limit switch. Something like this happens to me with photoeyes and safety relays. What gives?

 

[TheWaterboy]

Warranty must have JUST expired.

 

[Mickey]

Sunspots.

 

[TheWaterboy]

Global Warming

 

[parky]

It's a well known fact that even well designed products have a life cycle, for example a relay may have a guaranteed 300,000 operations many could last even longer, but some are not so good, for example we had 3 machines that were almost identical, two with Mitsubishi PLC's (Relay type) & one with an IMO the Mitsi's ran for 10 years without a failed relay (probably 30,000 operations per day), the other the relays would fail every 4 months incredibly you could almost set your watch date by them, we would replace the relays on the 4th month, all three macines would produce 30,000 products a day within very close tollerances i.e. the machine cycles per day were almost identical with the exception of faults on odd occasions, eventually, instead of fitting the exact make of relays we found ones that physically were exact same fit, never had ther problem again, I would personally have replaced these units with Transistor outputs but as usual the accountants had their say. So, it is probably due to either poor design i.e. wrong parts that will not stand upto the required intended operations or the design is wrong. so probably not you, just murphy's law.

 

[Ken Roach]

I try to play at being dead serious with my customers when we're doing particularly frustrating troubleshooting.

"Gremlins weren't endemic to central Florida until well after the war. Whatever you've got is descended from invasive colonies established in the Sixties, especially so close to the Cape."

 

[TheWaterboy]

... And all the lesser species have been killed off so you have a resistant genetic line here.

 

[Lare]

Planned obsolescence

 

[Ken Roach]

Five years ago I was sweating in a cleanroom "bunny suit", a few meters from the Sea of Japan, a hot and humid August day between Osaka and Kobe. I was leaning into a cutout in a machine frame (we built the controls inside empty spaces, not control cabinets) in the dark, looking at a safety relay.

It looked like it was breathing.

I mean, the input LEDs did. the Channel 1 input would, at intervals, glow slightly and increase in intensity, then dim and go dark. Every few seconds, but not on a perfect time interval.

The machine was shut off at the main disconnect. The machines next to it were shut off at their main disconnects. The incoming distribution vault was shut off at its main disconnect. All the lights in the building were shut off. All the air handlers were shut off. All the heaters, all the ovens, all the air conditioners. The adjacent cafeteria was closed. The streetlamps were off. My headlamp. My computer. My phone. The only thing within a hundred meters that should have had any chemical or electrical energy in it was me.

But there was that light, glowing and dimming.

I was able to get the safety relay to stop nuisance-tripping by installing a small RC network to bleed off that induced voltage in the e-stop series circuit. But it remains one of my most frustrating troubleshooting experiences. There was no reason for it, yet there it was.

ゴジラ.

 

[padees]

Its a silly question but I wonder if anyone else experience this... Our plants make thermostat devices, almost all of its parts made in house so we have a lot of different machines, new and old. Here is the strange part... More often than not, when I get service calls, within a span of 2 or 3 days, the nature of the problems tend to be very similar. Yesterday and today, I got four service calls, all for different machines; a metal-cutting saw, grinder, roll metal dispenser, stamping machine. All of them had a bad limit switch. Something like this happens to me with photoeyes and safety relays. What gives?

It's just the nature of the beast you are working with. That's all.

 

[Steve Bailey]

All of them had a bad limit switch. Something like this happens to me with photoeyes and safety relays.

The explanation for the limit switches and photoeyes could be due to the same forklift operator driving in the vicinity. Equipment failures sometimes follow certain operators like the black cloud over Li'l Abner's Joe Btfsplk.

 

[Rob...]

More likely explanation is the mind loves to see patterns in things.

An we aren't any good at statistics off the cuff.

How many times have you run into a friend in a random city unplanned. "small world huh". Well no, you just don't remember the millions of other random people you see.

 

[padees]

More likely explanation is the mind loves to see patterns in things.

An we aren't any good at statistics off the cuff.

How many times have you run into a friend in a random city unplanned. "small world huh". Well no, you just don't remember the millions of other random people you see.

As I mentioned, It's just the nature of the beast, and It's up to you to determine what that beast is.

 

[Puddle]

The machine spirit is displeased.

The one at my plant doesn't like the following:
-Replacing obsolete parts with currently available ones
-Running slow
-Grease

What it does like:
-Running absolutely flat out all week until it runs out of material to digest
-Panels that are inexplicably full of relays which switch four times per second
-Dust

We regularly see that if the production target is 100% of capacity, it will be nailed. If it's 60%, it will be a long, long week full of minor breakdowns which usually involve a part that's nigh-impossible to get hold of in the 21st century.

 

[cardosocea]

The only superstitious person I found took it really seriously so every time we had a new machine installed, he'd come around with holy water and sprayed it with it.

As to your example, I have a similar one. I worked in offshore drilling in West Africa. Our winches had proximity switches to assess the position and also to stop it before hitting the derrick. We had two winches, so 6 of these P+F proximity switches installed. One Sunday I get a call that one failed, when I get there I realise it's actually two and by the time I finished the call three had failed. All in, four failed on our ship that Sunday afternoon in sequence.

I didn't have four spares, so installed whatever I had in the warehouse and kept the machines running... come to my office thinking to write to the nearest ship to us (2 years newer) to pinch their stock thinking that since they have redundant proxes, they'll have enough for me to get up and running. Lo and behold, I already had an email from them saying that 8 of their 12 switches failed and they needed my stock to get back up and running.

Worst? Went to the workshop, wired the proximity switches and all of them were working but clearly did not work when in the derrick. We sent all of them to P+F in Germany and got told that these things don't like tropical weather and it's ikely the cause of the failure. Bear in mind that the proximity switches were installed nearly 2 years apart too.

it was one of the most stressful times I had but also pretty cool as I had them replaced without going into downtime.