For ICE vehicle production, there exist well-established supply chains and each generation of vehicles builds incrementally on the previous generation.
Yep. Most folks have already said it all so need to repeat it all.
Ramping up production is not as easy as turning up a dial to 10 or 11. The upstream suppliers (for everything from bolts and screws to plastic panels, switches, headlights, taillights, etc.) also need to ramp up their production as well, and they might have constraints in terms of production capacity (e.g. # of lines, amount of equipment factory space, speed of equipment and processes including quality control), staffing, hiring (where and how quickly can you hire possibly hundreds of worker (screen, interview, application, acceptance, start date, training, etc.), input parts and raw materials, etc.
What if the ramp WAY up only to have the orders fall off sharply or to have the buyer (automaker) suddenly say "stop! we don't need any more until ____"?
Only a complete car can be built and shipped to a customer if all its parts are ready and properly assembled. The part(s) that aren't ready for any reason (e.g. production bottleneck, low yields (too many defective parts), shortage of some component/input), etc. will likely hold up the entire car.
And, there's this problem:
Tesla's real capacity problem: Too many people.
For background, OP might want to watch these videos, even though it's Nissan:
REPORT: Oppama Style
For every one of the processes shown and not shown, someone had to come up with the procedures, train the workers, program the robots, set up the equipment (e.g. installing correct dies for stamping, installing correct nozzles for paint robots, etc). And, all the incoming parts need to be sequenced just right to be available at the right time and place.
There needs to be the right level of quality checks and statistical process controls in place. See
Door needs to be slammed to shut? on the latter, and if you don't have time to watch all of that video, just watch less of it via the time indexes suggested there.
Ford produces somewhere over 6 million vehicles/year and the other largest automakers (Toyota, VW Group, GM and Nissan-Renault Alliance) do about 10 million/year EACH. And, they've all been doing it for a VERY long time.
Every automaker has no doubt run into countless issues while producing prototypes, during pre-production and production phases. Every established automaker doing this for many decades and longer I'm sure has plenty of folks w/experience who have seen the problem before and has experience in what might work or not work to solve it.
I've (unfortunately?) never worked in the automotive industry but have taken auto plant tours of Toyota Tsutsumi, Mazda in Hiroshima, Nissan Oppama, Ford Rouge (they build the F-series truck there), NUMMI (when it was still NUMMI), BMW in Munich and Porsche in Stuttgart.
