I see robots/automation as a solution to a problem. That problem is safety. Either repetitive work that slowly breaks down the human, or "this is not good for you"-work that's directly dangerous.
I like that question from the sensei in that goldratt book: "did the robots make you more productive?".
Trying to invest your problems away is a waste of time and money if you don't know, and continously work with your processes. Or what they call kaizen in the article.
The big issue is improvement of standardized work. If you automate early you get tethered by subpar standards. This is natural when you have workers: you iterate work instructions and what tools to use together as a group. This is basically how Toyota is so good at producing: every worker know what to do and when to do it. They haven't always been like this; they have slowly iterated into what they are today.
Improving on work instructions for a robot is tideaus at best, and really, really costly as a worst case: you either re-program, or you're forced to reinvest if the robot isn't capable of the new movements/steps.
Musk also had to learn some lessons Toyota learned years ago, because he trusted a bit too much in automation.
If you want to automate something, you need to know exactly all the corner cases, every step of what the human is doing to make it work. The robots are precise enough, but it's often not that easy to describe the tasks to them.
Think about a company that produces screws, they don't have a program for every possible screw they make. Same goes for a more complicated item like a metal box with a door on it.
Robots also only really work in stop stations, not on moving vehicles (with a few notable exceptions like paint shop).
Does all of this cost more than hiring a person? More than twice as much?
How often does your automation fail? Is it more than 1 out of 1000 cycles? You have over 10,000 automation steps. That would leave 10 errors per vehicle. When automation fails, it often stays down for a while for investigation and repair. Any station down will stop all stations both before and after it (eventually)
With 10,000 automation steps, and a run rate of 1 vehicle per minute, how often can you lose a robot?
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Disclaimer, I work for GM; any opinions are solely my own.