Yeah, then that’s probably the River Rouge facility that you visited.
So…I’ll be honest - I’ve never actually done the public tour, but I’ve been through that plant, getting to other areas that aren’t open to the general public, on official, company related business.
Having said that, modern assembly plants (at least as I recall from my detailed walk through of GM’s Lansing-Grand River Assembly plant (which used to make the Cadillac STSes, but I don’t really know what they make nowadays) – a lot of them are structured like this:
There is a body shop area where the body-in-whites are assembled. Sometimes, everything is “dunked” into paint (well…that’s how it was like 15 years ago, now they probably spray), and so sometimes they would assemble the vehicle and the disassemble them for paint in order to make sure that everything fits first. Paint shops are also usually sealed in order to prevent contamination.
Then there are also usually two lines that run in parallel, but vertically (second floor vs. first floor). LGA had it where the chassis and underbody stuff would be assembled on the first floor while the second floor would assemble the body. Once they’re both built up, the conveyor would bring the body to be married with the chassis at which point the engine would basically slip in underneath the entire car and for example, again, if I recall correctly, they would drive the first 12 screws/bolts of the suspension strut into the body before anything else.
So in your game, you have those operations as being sequential to each other, but in many final assembly plants now, the reality is that many run in parallel. That’s probably what you were seeing with the conveyors. So, it’s not uncommon for the carrier (a.k.a. “clamshell”) to be carrying to body around for different operations (along with its associated parts). Thats probably what you saw.
Another example as I mentioned is that they might put the doors on the vehicle once to make sure it fits properly, and then take them back off for it to be painted (so that it will get exactly the same colour as the rest of the body) and then once it dries, might be sent so that the door could be built by adding the glass for the windows, motors, controls, switches, speakers, handle, latch, and door trim, for example, all separately before the door goes back to be mated back up with the original body that it was “paired” with. (Again, as I recall, LGA was set up that way.)
re: manual vs. automation
That’s actually usually quite the debate. A lot of people tend to think that many of the repetitive tasks (of which, there are countless), can be automated, but the reality is a lot more complex than that. Setting aside the human element for a moment, it wasn’t that long ago that Toyota and Mercedes, both replaced some of their automation by putting more people back into their respective processes probably because automation wasn’t helping them in those areas.
Elon Musk (Tesla) is famously having said that he was oversold on automation and he too, also had to hire more people in order to address the production problems that they’ve been having - the extent that he’ll talk about how he’s sleeping at the factory to get stuff done.
Musk fans thinks that’s nobility. As someone who’s been in the industry for a while, I think that it means more that he doesn’t know what he’s doing or talking about (because no other CEO has to PERSONALLY get involved like that which means that some of their processes are massively broken if the most expensive guy has to step in). But that’s just my take on it. (IF things work as they should, the CEO shouldn’t need to be at his own factory, fixing things.)
And the UAW would always want more people involved, so like so many things, there’s a time and place for it all.
The ground “belt” that you’re talking about - that’s also pretty much an industry standard as well, but to varying degrees. Some would have a lift so that it would raise or lower the height of the thing they’re working on in order to accommodate the worker, while other resolve this using alternative methods/means. So it depends. In-ground conveyor systems tend to be favoured, mostly due to their load carrying capacity. You’ll also note that some final assembly plants, where the workers stand, they’re also standing on a moving conveyor belt as well so that the car is never actually, truly stationary.
Some of my mates in university studied industrial engineer, and went on to become some of the engineers that would be part of the team that would design these plant systems. If you think engineering a car is difficult, try engineering the stuff that’s needed to build said car. It’s quite the sight to behold.
If you get a chance to visit as many plants as you can, you should take every opportunity you are presented if this is something that interests you.