Production & Design

Ignore this one Ooopps

My PC's throwing a woblly

Isn't there an old quote/saying that goes something like...

"No matter how idiot-proof you make the design, there will always be at least one idiot that can break it."

I designed the control system for a moving test fixture that could easily injure/maim/kill someone if it was abused or malfunctioned. Ignoring many comments of "you don't need that", I used 4 layers of "stop" protection. A kill switch at control panel, primary and secondary stop sensors on tracks, and "Oh SH#T!" stop sensors at the END of the tracks. In 12 years of operation, we only had one incident where the carrier reached the "Oh SH#T!" sensors at the very end of the tracks and was stopped before any damage or injury occurred. Someone had opened the control panel to make an unauthorized adjustment and accidentally fried the controller board with a large "static discharge". I never planned for that, but the redundant safety features I used still worked. I consider myself lucky that the system wasn't tested by a better idiot.

Hi MJB,

If you consider people as IDIOTS, they will be as you want for you. The creator or manufacturer of your equipment was a human being helping people and you to do something valueable, isn't it?

So, you improve your equipment to be better, and someone, later by using it will discover that your improvement wasn't perfect, so someone do another improvement. This is the way of life in both side of your machine. Let people to improve it and also let them criticize or misuse, Gil.

NB: Don't forget to improve again!

The quote I always liked is....

"As soon as you make something idiot proof, the world makes a better idiot."

This was much less dramatic in effect, but still enough to stop a system ...

A PLC running an unwrapping machine ran happily for 4 years. Plenty of minor mechanical and electrical problems, most fairly easily fixed (worn bearings, broken sensor leads etc.), but no trouble with the PLC.

Then one day it faulted. On investigation, the monitoring I'd included to keep running totals of total ops, successes, failures etc. halted with an overflow. I'd only allocated a 16-bit signed integer counter for the number of times the START button was pressed. On the 32,768^th push - Overflow!

I'd allowed long integers for the total number of unwrapping operations (which was up to about 500,000 and climbing steadily) but had overlooked the number of STARTs required.

A full 25%-30% of the programming I do involves making sure that external data is viable - particularly data entered by operators. Silly stuff like: NO, I will not accept that the month is 15, the switching point from using one chemical tank supply to another cannot be 0.0" (on a 30' tank)...

An old story I heard 35 years ago working in a Copper processing plant:

Trying to find ways to increase production the company hired an outside efficiency consulting firm. First they brought in an accountant and gave him 3 steel ball bearings. The accountant took them, added them up, then moved them off to the side one by one until the balance was zero, then he sat back happy. They then brought in an Engineer. He took them, lined them up in the vertical, horizontal, angle, and finally in a triangle pattern, then he sat back happy. Finally they brought in an operator. He broke one, he lost one, and he took the third home in his lunch bucket!

2 years ago I started a new job with this company. I was tasked with building a control panel for the Quarantine room. After 2 weeks of trying to pry all the information out of these folks I again went to them and stated all required operations this panel had to do. I did this with each of the 5 people involved and was told yes, that is all. So I put the BOM and sent out for quotes. Ordered, fabricated, installed and connected all pumps, heaters, UV's, and Ozones. Weeks later they added so many more components I now have 6 enclosures on the wall and conduits everywhere. Next panels became 60" X 48" X 20" after I again was told all that would be controlled by those panels. And again in the weeks following, I have added so many more to these panels, but had the room and still have a little room left.

I am now in process of designing a control panel that will be used to start the 4 500KW gen-sets, Open and Close the 4000A Utility Breaker and Transfer Breaker in our switchgear. Being I know the people that will ultimately be operating this panel when the utility is down and re-transfer back to utility when it is back on line. What should have been a simple $300.00 panel is now an $1100.00+ cost with all of the redundancy I have added so there is no possible way that both breakers can ever be closed at the same time. And as much as I think I have this so idiot proof, I am going to also add 2 more push buttons that also have to be pushed at the same time as the closing button for that much more redundancy. What I have learned in the past 2 years: No matter how hard you try, YOU CAN NOT FIX STUPID.

I've finally come to the conclusion that the idiots sorry production workers are far more ingenious than engineers. No matter what we do they'll find a way to bend, break, loose or misinterpret it.

I started in the quarrying industry, give a bunch of idiots giant Tonka Toys and just watch the fun http://outdoors.webshots.com/album/556596065SjrGYz
My electricians mate parked up the pick up, came back to find it as flat as a pancake. The driver of the 170-ton dump truck never even noticed as he backed over it!

There are people who walk up behind graders, dozers and on the 'boom side' of excavators that become 'formally' a qualified tradesmen, or university graduates.