I guess I am going to add my 2 cents worth of info.
First, I really like this update and am very pleased that we are now 3 days out and no major glitches!!! Thanks for new crops. YAY!
I do not have all of the facilities that require metal, (car parts) but do have all of the others, including the newest Explorer Accessories Factory. I have only ONE of each facility. I just
calculated that I need 1920 sheets of copper, 4590 sheets of Stainless Steel and 4710 sheets of Aluminum just to fill those one time.

I also calculated that the mineral mine can only
produce 28,980 iron ore, 4200 chromite ore, and 15750 copper ore in 7 days. (the limit) And the open-pit mine will
produce only 4200 Aluminum ore in 7 days. (YES, I KNOW that I can keep clicking every day to keep it in max production)
I agree that the metal factory is really not the problem, since we COULD keep it filled, and post often to let neighbors work for us....IF WE HAD ENOUGH RAW MATERIAL!
I REALLY don't like having multiple mines on multiple farms for the same reason most have said. They simply don't fit with my farm theme.
I don't understand the devs reasoning (I'm sure it is a good one) why our neighbors are not allowed to help with the production. If they cost FC, like the semi-truck does, I could almost understand. (They want everyone to buy a semi-truck to get their supply of meat, leather, etc.)
But the mines are for coins, and if neighbors were allowed to work them, it SURELY would help somewhat with the production problem.
My suggestion is to either increase dramatically the output from the mines, or let neighbors work them. Please??
Thanks,
Deborah