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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I'm NOT denying or disputing your comments. Your analysis may well be more accurate than mine. As an electronics engineer who "cut his teeth" designing high power (1 KW >< 10 KW) / high frequency amplifiers (2.0 MHz >< 400 MHz) for radio communications applications many decades ago, I VERY WELL understand proper grounding, spurious radiation, random noise, etc. Considering that the subject was a "K-car", built in the early 1980s, the level of sophistication of control of robotic devices was at the same level as today's technology. At this point, it doesn't make a lick what the cause was, since it is ancient history. It remains a story for entertainment at most.
I had several instances where the robot was accused of incorrect or random wrong positioning. The root causes were bad parts, inconsistent presentation tooling, human (loading) error, or a damaged end-effector / end-of-arm tooling. The robot controller and mechanical arm ALWAYS went to the correct position.
All of the servo systems that I have seen rectify the AC source to DC, and then chop it to high frequency AC. The AC supply would have to be so bad as to cause the robot controller to shut down to cause a problem. Yes, then you would have a problem; a dead robot, not a random misplaced weld.
How about one of the parts in the assembly was in error and that a chain of construction caused a weld flange to be in the wrong position? To quote an earlier post, a human welder would have just adjusted his bead.
Good point, Old Curmudgeon. There's a very good chance that is exactly what happened. We can see from the Sherlock Ohms entries, the source of the problem is often surprisingly simple.
While many of the comments are interesting & pertinent to the probable cause of this manufacturing error, COULD IT BE, given the era of robotic manufacturing, that there was a power glitch in the power line feeding the robot which caused it to make an errant motion along one of its axes? Considering the overall environment of a major assembly line, it is highly likely that the A.C. power lines were highly toxic w/ noise from multiple sources.
Many of us have experienced non-reproducible glitches occurring in systems design during our careers, I suspect this incident may be classified into this category also.
Andrew; I worked in the General Motors Scarborough Van Plant, and the Oshawa Truck Plant, and at a couple of suppliers, and I have seen some robot applications.
The Van Plant had ABB IRB 2000's using 'seam finders' to find the overlap of the metal pieces to lay the MIG weld. One of the problems was some of the parts were designed for right-side-up manual welding. The robots were trying to weld the same fit-up upside-down, which caused major problems.
Quality improves with robotic applications, because robots don't work with 'junk' parts - the parts and the fixtures must be right. Humans can (and do) compensate for poor fit-up.
It was always a problem, as a 'robot programmer', to try to educate engineers as to the correct application of robots. And many times, I had to 'defend' the robot, and prove the problem root cause was bad parts or poor fixturing.
exactly.. which is WHY robots crash... unless there was a way to SEE that it was not correct.. and there are systems for that but right now our technology isn't the best for this.
Right if we had manual welders doing this job it would not be missed, but we do not have to pay the robots to do almost a perfect job all 3 shifts with out breaks :/
Yes, Chuck, it was Iacocca. He first proposed the concept when he was at Ford. They said no. When he was at Chrysler, he implemented the K Cars successfully. It could have been the timing, since it was an American response to the booming Japanese cars. Iacocca's bigger success, though, came with the Caravan and Voyager minivans.
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