love that e-stop

dlweber said:

I hate when operators use E-stop instead of cycle stop, especially since a lot of what I work on is robotic

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All you got to do is design it so that the operator has to set up everything from scratch again whenever they hit the E-Stop. They'll learn.

Jeev said:

I was on site recently to do some program changes. Upon opening the cabinet I noticed some odd wiring, and checked the program to confirm... Yep, safety contactors removed from the safety relay and now put on the PLC outputs, feedback from the safety relay on a PLC input and some timers that made absolutely no sense whatsoever in the code. Effectively, they put a TON between the safety signal and the contactors, but the way it was written assumed that one contactor was for E-Stops and one for guard doors.

Moral of the story. We should stop putting E-stops on machines and let the problems sort themselves out. "I might be a commissioning engineer, but I can't fix stupid."

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That sounds like something highly illegal and if there was an injury or death there'd be serious consequences. The good part of it for you is that clearly the machine was tampered with and the company changed the design specifically making it unsafe, so all the heat would be on them, essentially.

ppb1487 said:

Its quite funny to see the machinery that is around me at the moment does not even have an E-Stop. There is a Red Mushroom push button but the operators use it as a means to stop the air in the pneumatic cylinders.
And these machineries have been running since the past 15 years! Perhaps no one cares!!

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Just because something works doesn't mean it was built correctly and/or safely. This is doubly true with anything electrical. Just because your machine has been running for 15 years doesn't make it safe. It may kill someone tomorrow or it may go into the scrap yard 20 years from now without injuring anyone. For the company that owns that machine, they're taking a gamble. So far, they've won. I don't know how things are where you live, but when someone gets injured or killed on the job here in the US or Europe, the company has to pay big money in fines, workman's comp, insurance, etc. This is often to the tune of hundreds of thousands or even millions of dollars.

So, yeah, a company can save a few thousand bucks on a machine by not having any safety equipment installed. Then, if or when someone gets killed by it, and OSHA or whatever other governing agency fines them a few million bucks, they'll realize that all they did was spend a dollar to save a penny.

I'm just glad the engineer that designed one of my lines put an aux contact and wired it to a seperate input on each so I can quickly tell which one of those 14 estops were pressed.

If you're trying to engineer your machine to estop smoothly, you're missing the point, IMO. If the results of an estop are messy and kill production, remember they are only for.... (wait for it) EMERGENCIES!

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I am not trying to engineer the cell to estop smoothly, the reason I hate it (other than the obvious misuse of an estop) is it jerks the robot to a stop, kinda the opposite of smooth. I have thought of making a deterrent to using them but the setup is minimal on the cells, so not much to use as leverage.

FactoryTalktotheHand said:

That sounds like something highly illegal and if there was an injury or death there'd be serious consequences. The good part of it for you is that clearly the machine was tampered with and the company changed the design specifically making it unsafe, so all the heat would be on them, essentially.

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That's why my first action was to inform my project manager, and then the customer in my site report. I don't know how relaxed the legislation or regulations may be in that particular country, but it's typical to see this sort of stuff, or machines being operated without guarding for "Easy access" in many parts of Asia.

Worked with a guy a couple of years ago; he was with the company for 15 yrs. before they let him go. He was installing a new PLC into a machine and was supposed to correct and update the magnetics cabinet in the process. This included the new installation of a safety relay. I asked him if he knew how to install the unit, "yea, no problem, I got this." Five weeks later when the machine was still not running and he had been fired it all fell into my lap. The entire cabinet looked like a spaghetti bomb had went off and every time you pushed the E-stop button it killed control power to the safety relay.

Worked with a guy a couple of years ago; he was with the company for 15 yrs. before they let him go. He was installing a new PLC into a machine and was supposed to correct and update the magnetics cabinet in the process. This included the new installation of a safety relay. I asked him if he knew how to install the unit, "yea, no problem, I got this." Five weeks later when the machine was still not running and he had been fired it all fell into my lap. The entire cabinet looked like a spaghetti bomb had went off and every time you pushed the E-stop button it killed control power to the safety relay.

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Well least you know if the safety relay caught on fire it was easy to isolate its power...

I am rewiring a control panel now....
The E-Stop was ONLY AN INPUT to the PLC and the plc code turned off the outputs.

I'm going to do like the OP...

An Emergency Stop push button is not a safety device.

Discuss...

Geospark said:

I'm going to do like the OP...

An Emergency Stop push button is not a safety device.

Discuss...

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I've got one......

I'm crazy about those motion controllers!

Thoughts......

I believe it is classified as a complimentary device.

If my memory serves me right safety devices are devices that make a process safer, ESTOPs do nothing to make the process safer they are in place to minimize damage or injury in the case an unsafe event takes place or is imminent. Safety devices (once implemented) should be passive.

How did I do Geo?

I've enjoyed this thread on e-stops with all illegal, stupid things that people do. However, I think I might have the best one. A machine that a customer had me retrofit had a lighted red mushroom PB to START the machine. The light even came on while it was running. So it was basically an emergency start button.

Geospark said:

I'm going to do like the OP...

An Emergency Stop push button is not a safety device.

Discuss...

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Well the guy whose arm was caught in a conveyor (due to a bad hand placement while tracking the belt) might disagree with you. A belt was used to stop the bleeding enough until the ambulance got there.

The Estop did just what I explained, light curtain that would of shut the conveyor down before he got his hand stuck in it would be a safety device.

The Estop made nothing safer it just minimized the damage once the accident happened. Safety devices are to prevent accidents.