Nearly everyone who’s driven the new F25 X3 has remarked upon its solidity and high-quality feel. Indeed, the new X3 might be the best-built BMW ever thanks to an unprecedented degree of automation in the body assembly process. By using robots to perform tasks previously done by humans, BMW is achieving greater precision while also reducing the injury rate among assembly line workers.
“We’ve gone from about 30% automation to about 98%,” says Bobby Hitt, spokesperson for BMW Manufacturing in Spartanburg, South Carolina. “What we really see the machine as doing is helping us with increased volume and quality. Humans can’t do what those machines do.”
What the machines do, of course, is to build new X3s to an exacting standard, something for which the original X3 wasn’t really known. To improve the vehicle once built under contract by Magna-Steyr of Austria, BMW brought production of the new F25 in-house to Spartanburg, to the line that built first-generation Z4 roadsters. (Production of the second-generation Z4 now takes place in Germany.)
Normally, the introduction of a new model would mean a complete line replacement using all-new equipment. For the F25 X3, however, the associates (as BMW terms its employees) managed to engineer a state-of-the-art body assembly line using much of the existing equipment from the old Z4 line: conveyors, platforms, lights, air lines and even 120 assembly robots.
“With each life cycle, we’re keeping our assets, spending more wisely on capital investment and integrating more components into the existing line,” says Chad Johnson, project manager for the X3 body shop. “It makes it more difficult for engineering, but the capital savings should get us into a better position.”
Instead of donating them to a technical school as might otherwise have been done, BMW was able to refurbish and reprogram 120 assembly robots from Z4 production to build X3s, extending the life cycle of each robot from seven years to 15 and saving millions of dollars in the process. Built by ABB of Norway, the six-axis robots could actually be used far longer were it not for advances in control technology.
“After two life cycles, there are so many technology changes with the IT, not the hardware, that you have to ask whether it’s obsolete or not,” Johnson says.
Even though they’re no longer new, the robots are performing cutting-edge functions designed to increase the accuracy of X3 body assembly while improving ergonomics for the line workers.
“Traditionally, a lot of the robotics were driven by the way we used to build cars,” Johnson said, explaining that body shop workers had previously been required to lift heavy weld guns and large parts like hoods and tailgates, which often led to injury.
Humans were eliminated from much of the welding process some years ago, and these days, they MIG-weld only a few spots the robots can’t reach. The X3 line takes that a step further by having the robots do the heavy lifting, as well. Where assembly line workers were previously required to handle heavy objects like the 45-pound doors whose weight is compounded by an awkward size and shape, today that work is done exclusively by robots, leaving humans to lift nothing heavier than a screw gun or the front fender that weighs just seven pounds.
In addition to their ergonomic advantages, robots perform their task exactly the same way every time, improving the quality of construction by eliminating a variable.
“From a quality point of view, to make a process repeatable by a human being is very difficult,” says Don Dickerson, who led the design and engineering of the X3 production line. “The fitting process is very difficult, and it has to be performed precisely to eliminate variations. With a human, you add a massive variable.”
Part I: Body