In the 1980s, GM spent $45 billion replacing factory workers with robots. One of its own executives pointed out that was enough money to buy Toyota and Nissan outright. The robots painted each other and welded car doors shut. What Toyota did in the same years is the part worth studying. In 1984 it took over GM's worst plant, in Fremont, California. Same workforce that had 20% absenteeism, almost no new automation. Within two years that plant was building the best quality cars in GM's entire…