When my father took delivery of a brand-new 1981 Reliant K Car, he asked me to give him a ride down to the dealership to pick it up. Everything went fine as he pulled off the lot.
As I followed him home on that maiden voyage, I couldn’t believe my eyes. The car's muffler and tailpipe fell off on to the road in front of me. It was a good thing I was there to stop and block traffic. He pulled over to retrieve the errant equipment. Once we had picked the muffler and tailpipe off the road and dragged it to the side, we inspected the clean equipment to see what the problem was.
We both laughed heartily when we realized what the problem was. That very morning, my father and I had been talking about recently deployed robotic welders on automotive assembly lines. We discussed the speed and precision of the new robots. The robots were able to put a bead of weld on a sheet metal seam at good speeds without missing a spot.
As we stood on the curb that day, neither of us could believe that the perfect bead of weld was precisely one inch from the end of the muffler tube. The bead was fine and tidy. It just happened to be in the wrong spot, thus completely missing the spot that would attach the muffler assembly to the car. It simply didn’t manage to do its primary job of keeping the muffler from falling off.
The errant weld on the Reliant K Car must have been an isolated instance, as my dad didn’t receive any subsequent recall notice to correct the muffler and tailpipe weld. Apparently, it was just one robot having a difficult day. I guess monkeys cause problems in the robotic world, just as they do in the human world.
This entry was submitted by Kevin Otte and edited by Rob Spiegel.
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That was 30 years ago, which was around the beginning of the age of robot welding. Since this type of story didn't become widespread -- this is the first I've heard of an incident like this -- I would imagine the robots generally did a better job of getting the weld on the right spot.
Didn't K Cars have a reputation for fairly, how shall I put this, low-end craftsmanship? Even so, very good illustration of the super simple miscues that plague even the best and brightest technologies. Also shows how far robot technology has come over the last few decades. An entertaining tale!
I think you might be correct, Beth. Growing up, my family had a K car wagon and I seem to remember being broken down on the side of the road a lot. That said, it's not too hard to imagine that a robot could, even today, miss a step no matter what assembly line it's working on. After all, nobody/nothing is perfect.
I am a Robotic Welding programmer and to give a little bit of insight... The robot never "forgets", but what usually causes this type of thing to happen is that when the muffler came doun the assembly line it was probably not in its correct location, meaning not in the fixture correctly in the first place. That would cause this too happen.
All parts are not the same, as my company also stamps parts, an employee might not have seen a defective part which was longer and passed it through. Every day I find my self "editing" programs because the parts are just not the same.
And finally a cause for this are possibly 2 of many other things such as.. The robot crashed on a previous part and it through the "TCP" off (tool center point). this would throw the welding "goose neck" off by a few cm or an inch. This problem would have to corrected by me and would take some time adjusting back. Another problem is the Welding "whip" which is where the wire is fed to the contact tip could have caught on an object from whipping around and snagging. That would cause a "close linned" effect and prevent the robot hitting it's weld point.
Robots are only as good as their fixturing. A great robot that has poorly designed or weak end of arm tooling will be non-repeatable and can miss welds or part placement. Part nesting is also a key component to a quality robot cell.
I think the type of mistakes is what differentiates robots from humans. A robot is going be more consistent. Therefore, if it is programmed correctly and the task is a repeatable task with little variability the robot will consistently perform the task. However if you program the robot to do the task 1" off. Iit will do it again and again.
Humans on the other hand have the ability to adjust from situation to situation but the variability in human performance can make it not perfect.
These two simple principles are just a few of the things a good design engineer will realize when they are putting together the design of the part. How is the part going to be assembled? Will it be with human labor or automated? What are the strengths and weaknesses of those assembly techniques and how does your design integrate with them?
Good points Robo Weld. Sounds like a number of things could have caused the weld to hit the wrong spot. The computer running the robot is literal. It will do what it's told, whether the parts are in the right place or not.
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