Production & Design

[Knobhead]

This must have happened to some of you.

You’re asked to design a control system for a machine, you think you’ve taken every thing in to account. Finished you hand it over to production.
You’ve taken every thing in to account?

I’ll start the ball rolling:
The foundry I worked at had an extensive rail system, all points on the main run were electro/hydraulic operated by the loco driver via a “slap” push button mounted on a post at the side of the track. All the driver had to do was hit the button as he drove past if he wanted to change the points direction. Signal lights were at the side of the points and repeated on a post showed the direction.
Over time the original control panels began to fail so I was asked to build new panels for them.
Now this may seem a weird way to go about it but I used a PLC program for the original design and then transferred it to relay logic. It meant I could make changes quickly.
Back to the story, all panels in and working for about 6 months without trouble. I arrived at work one afternoon to find the place in chaos. The one set of points that there was no alternative rout around had a 60Ton iron transfer car and loco derailed across them.
So what had gone wrong? The driver of the loco had hit the “slap” button that hard he bent and jammed it so the points are turning Left, Right, Left, Right. During change over the signal lights turn off to indicate no clear road. No clear road, did that stop our intrepid loco driver, like hell it did! So he arrives at the points pushing the transfer car. First axle goes left, second right, loco left!
It only took a one shot timer to sort the problem.
I hadn’t taken in to account just how brutal, heavy handed and stupid our operators could be!

 

[Deleted member 26818]

Place I worked at, had high speed shutters that worked off of pirs.
The fork lift drivers would race the shutters to see if they could catch them.

 

[MarkieSparkie]

I used to design electrical and electronic equipment for the Royal Navy, it was build in the normal way to industry standards for experimental trials, but before going into production always had to be 'Jolly Jack proofed'. Everything fail-safe, large panel warning lights and covered switches, etc. I swear they could destroy equipment just by looking at it. If a push button switch required a finger to operate it, you could guarantee someone would use a stick. You get the picture. Of course the poor old tax payer had to pick up bill for all this over engineering.

 

[Knobhead]

You can’t break that it’s totally indestructible!
Give it to a production worker, he’ll find a way!

 

[Deleted member 26818]

Reminds me of Tonka toys.

 

[grantr37]

This must have happened to some of you.

You’re asked to design a control system for a machine, you think you’ve taken every thing in to account. Finished you hand it over to production.
You’ve taken every thing in to account?

I’ll start the ball rolling:
The foundry I worked at had an extensive rail system, all points on the main run were electro/hydraulic operated by the loco driver via a “slap” push button mounted on a post at the side of the track. All the driver had to do was hit the button as he drove past if he wanted to change the points direction. Signal lights were at the side of the points and repeated on a post showed the direction.
Over time the original control panels began to fail so I was asked to build new panels for them.
Now this may seem a weird way to go about it but I used a PLC program for the original design and then transferred it to relay logic. It meant I could make changes quickly.
Back to the story, all panels in and working for about 6 months without trouble. I arrived at work one afternoon to find the place in chaos. The one set of points that there was no alternative rout around had a 60Ton iron transfer car and loco derailed across them.
So what had gone wrong? The driver of the loco had hit the “slap” button that hard he bent and jammed it so the points are turning Left, Right, Left, Right. During change over the signal lights turn off to indicate no clear road. No clear road, did that stop our intrepid loco driver, like hell it did! So he arrives at the points pushing the transfer car. First axle goes left, second right, loco left!
It only took a one shot timer to sort the problem.
I hadn’t taken in to account just how brutal, heavy handed and stupid our operators could be!

sounds like he was behind schedule and was angry as well, so just kept racing on... 60 Tons? Splat!

 

[Spoon]

A bit ago we had problems with the guys on the printing press hitting the emergency stop (also used for maintenance & cleaning the units, to stop any movement) so hard and that the contacts came off the stop button behind the control plate. Had to tell the manufacturer of the pushbuttons.

 

[malcolmsanford]

When I was doing my apprenticeship we had loads of conveyors dotted around the place. There was one that must have been easily 700 yards long and the start stop button was in the formans shop. dotted along were emergency stop buttons but if these were used to stop the belt it would sound off an alarm in the formans shop and all hell was to pay.

The belt had a huge motor which was fitted with a slip clutch arrangement, that if the belt snagged or caught, instead of the motor seizing up on the bearings and then burning out it will slip and the belt would just stop and ride over the clutch . I had the job with the sparks to change sections of the conveyor one day, and as we were taking the old part off I noticed loads of little holes in the belt all over just random. what are these I asked inquisitive apprentice as was, the loonies stop the belt with knives pushed through the belt into the rubber below on the table ...........................

 

[Knobhead]

A bit ago we had problems with the guys on the printing press hitting the emergency stop (also used for maintenance & cleaning the units, to stop any movement) so hard and that the contacts came off the stop button behind the control plate. Had to tell the manufacturer of the pushbuttons.

That is down right dangerous. BUT if things come to push and shove it shouldn’t have been in that state. If an E-Stop falls apart it breaks the circuit!

 

[Spoon]

That is down right dangerous. BUT if things come to push and shove it shouldn’t have been in that state. If an E-Stop falls apart it breaks the circuit!

The problem was mate that the whole contact assembly behind the switch came away from the front mushroom button, so the wires were still connected. The safety relays still saw the N/O and N/C contacts 'correctly.' It was like the pushbutton hadnt been pushed. Very dangerous. The only indication was that the Safe and Ready lights were not showing what they should have been.