Smart machines/PLC overlap?

[Tharon]

I stopped building systems without HMI's (Human-Machine Interface, btw) a long time ago because that's a great place to show why a system is not doing what it's supposed to be doing. I've designed systems where fully 1/4 to 1/3 of the program in dedicated to monitoring or alarms. A properly used HMI will let operators know if they should correct a situation or call for help. It can also let Maintenance know what to go look for, thus, in both cases, decreasing downtime.

Production data can also be displayed on the HMI and let's not forget about batch processing and recipes.

I work with some pretty simple machines, very small hydraulic punches, drillers, etc. Each machine has a small HMI. The Monitoring/Troubleshooting/Production Reporting portions of the program make up well over 75% of the program. The rest is a simple 5-15 step state program.

We have to cater to the lowest common denominator. Lack of training for production employees forces us to tell the operator word for word exactly what the machine is trying to do and exactly what sensor is not in the right state, and reasons why it may not be in the right state.

 

[Rube]

We have to cater to the lowest common denominator. Lack of training for production employees forces us to tell the operator word for word exactly what the machine is trying to do and exactly what sensor is not in the right state, and reasons why it may not be in the right state.

I understand your point Tharon but "the lowest common denominator" actually goes hand in hand with "I don't have a clue, I'm not technically inclined". or similar.

In reality, machine or system operators in all lot of cases just "turn 'it' on" and 'it' goes and does its thing--all day, all night. That operator on a pick station, for instance, might be the most productive picker on the shift but can't tell you what a PLC is. If they have a problem it's "I don't know what's wrong--it just stopped". They may be intelligent; just in another field.

I have obviously run into the smart guy/gal that wants to tell you what to fix when you get there and they're WAY off base. I had a Manager (who got hired on 9 months after the commissioning of a large conveyor system) try to tell me what had been occurring at shift change several times a week on that system. He actually proceeded to tell me what I should do to fix the anomoly. He had worked around conveyors all his life and knew what to do--lol. After a VERY patient 4 minutes of listening to him impress himself with his wisdom, I finally interrupted him and told him that I had designed the system, built the system and tested the system. I also told him that if his second-shift order picker would stop hanging her sweater on the red emergency stop cable on the conveyor next to her workstation the intermittent conveyor stops would go away. After a bit of non-technical training, the order picker stowed her sweater elsewhere and the stoppages ceased to occur. She was, however, consistently the highest producer on the line.

We program our HMIs down to the word, like you, when possible. If it's a jam on a conveyor, we have screen on the HMI that displays a "looking down" view of the conveyor with a flashing dot in the area of the fault. The HMI will also display something like "Jam at Pusher #2. If it's a tripped overload inside the panel we tell the operator to call maintenance and when they arrive, the HMI will tell them which one.

HMIs cost money up front but I would hate to think how much money and time would be later spent diagnosing a system without them.

 

[Tharon]

I really meant the people in charge of repairing and setting up the machine. Ones that should at least know what the machine is supposed to do.

Like just last night, I got a call from one of the off shift maintenance crew that one of the machines weren't working. A rodless cylinder would push a part, then retract, and then jump forward 2-4 inches. The HMI would tell them that the cylinder is not retracted, so it can't continue on. I told them to check for an air leak on the cylinder that would be causing it to move once the valve turned off. They argued with me for a few minutes about how that wouldn't cause it. Finally convinced them to check, they did, it was an air leak, they patched it and away the machine went.

It just seems to me like they (management) seem to think that HMIs can replace proper training and knowledge. The more "complete" the HMI is the more likely they think they can just hire anyone to take care of it without any technical know how or any training from production on how to properly run the machine.

It has got to the point that even on machines that state exactly what is wrong, the people in charge of repairing the machine still have to call and say "Ok, it says this isn't where it should be. What do we do now?".


(Sorry, a little off topic rant about companies not wanting to spend time/money on properly trained employees).

 

[Rube]

I really meant the people in charge of repairing and setting up the machine. Ones that should at least know what the machine is supposed to do.

It has got to the point that even on machines that state exactly what is wrong, the people in charge of repairing the machine still have to call and say "Ok, it says this isn't where it should be. What do we do now?".

How right you are--that's funny as hell!

Nothing amamzes like when a tech calls and says the HMI is telling him what's wrong but he doesn't know what to do.

Typically I 've been the technician AND the builder/programmer and maybe that gives me an edge when it comes to diagnosing problems. But come on guys--my HMI has partially diagnosed the problem! Now it's time for them to earn their money (and a little respect, maybe?).

I still stand behind the moniker on my signature--"Automation is not a corrective action for a lack of discipline". That was born out of just such a scenario. We can't make 'it' stupid-proof...

 

[carwashblues]

Funny stories. Reminds me of my automated test station days. We had a technical term for those situations, "operator headspace"! Anything and I mean anything the computer didnt do automatically and was up to the operator was a certain service call sooner or later.

All they had to do was drop a fixture into the I/O part of the station, pull a lever locking it in place, and hit a green run button on the console and the computer done the rest. HP equipment is state of the art and the operator tasks were as minimal as possible.(almost)

The HP engineers made one assumption too many however. The lever to lock the fixture in place and establish electrical contact between the fixtue with the thing being tested on it and the test station was just a lever operating a rod that used an overcenter cam approach for the task.

Well the lever had no microswitch to tell the computer it was engaged so If the operator dropped the fixture in and didnt pull the lever and started the test run, the computer would see everything open and abort.

They would call maintenance and go take a smoke break.

Literally 3 steps here. 1) drop fixture into its hole, 2)pull lever, 3) hit green button on console. (green button eliminated typing "run" on the keyboard, thank God!)

When there was a real problem I wished they all smoked because the ones that stayed liked to watch over your shoulder and keep telling you what the problem might be and always seemed to think whatever was wrong last time when they watched over anothers techs shoulder just had to be wrong this time too. Heaven forbid you didnt just take their word for it and pull the gear out that failed the last time supposedly.

Anyway, I blame HP. Operators cannot be relied on for any task where a decision they make has any possible negative outcome. The engineers at HP assumed the operators would pull a lever and caused a lot of downtime as a result.

Hopefully on the newer stations, all you have to do is drop in the fixture and hit the green button and a solenoid automatically locks it in and runs the test.

We couldnt modify the software to display a "check the freakin handle" message flash on the screen because of red tape. To change a production program you had to go thru more bureaucratic hoops with the Navy and all so it was easier just to pull the handle for the operators every now and then.

 

[bulletin blues]

Best wishes CWB!

 

[carwashblues]

Thanks BB!