GREER, SC – Who would have thought a decade ago that a medium-size German auto maker would be among the top U.S. exporters of cars?

For the third consecutive year in 2012, BMW’s assembly plant, located in Spartanburg County, led the U.S. auto industry in exports. The year’s total rose to $7.4 billion as an estimated 211,000 X3, X5, and X6 cross/utility vehicles were shipped to 130 countries. The plant turned out a record 301,519 units.

In volume terms, Ford was the leader that year, exporting 371,409 vehicles, although they were from multiple production sites.

BMW says a $900 million expansion, raising cumulative investment at the plant to nearly $6 billion, will boost capacity once again to 350,000 units in 2015. And with it will be the addition of the new X4 reportedly due out in early 2014.

Through June, the factory was on track to build more than 325,000 units this year.

The Spartanburg facility comprises more than 1,150 acres (465 ha), including 4 million sq.-ft. (372,000 sq.-m) under one roof. It consists of three main shops – welding, painting and final assembly. Stamping is done by suppliers.

The plant produces the X3 and X5 Sports Activity Vehicles, X5 M, X5 xDrive 35d, X6 M and X6 Sports Activity Coupe.

The auto maker operates about 750 robots, including 400 in the 3-year-old X3 shop. The plant introduced its first unit welder in 2010 with the launch of the X3. Prior to that, main body components were welded together manually. Welding now is 98% automated. The unit welder is supplied by Kuka.

Unlike Japanese and Korean auto makers setting up shop in the Southern  U.S., BMW outsources stampings mostly from local suppliers such as Spartanburg Steel Products and Spanish transplant Gestamp South Carolina.

In the 700,000-sq.-ft. (65,030-sq.-m) paint shop in which 90 robots and six miles of conveyors are installed, the auto maker has integrated primer-coat and topcoat processes. The result is that three of 12 steps have been eliminated, including primer, primer-over and primer finish, along with one of the shop’s ovens.

Combined with the installation of new robots and improvements in ventilation technology, energy consumption in the shop has been reduced 30% and carbon-dioxide emissions more than 40%.

The paint- shop expansion, which began in 2008, was completed in 2010. Much of the process technology came from BMW’s Oxford plant in the U.K., where the auto maker manufactures the Mini.

BMW U.S. spokeswoman Kelly Wamsley says productivity increased 40% and process time per vehicle was cut 80 minutes. Each car receives five coats – phosphate, electrodeposition, two base and one clear.

Unlike most Japanese and Korean auto plants setting up shop in North America, Spartanburg does not make components in-house with the exception of doors and instrument panels.

The door subassembly line consists of four sub-lines, one for each door. Wamsley says ‘supermarket kitting’ is used to supply need parts to the lines. Front doors go through seven stations each, rear doors, six. The operation assembles nearly 2,000 doors a day.

BMW has about 40 suppliers in the state and 170 throughout North America. Included are Alps Electronics (audio equipment), Autoliv North America (airbags), Calsonic Kansei North America (compressors), Lear (seats and body control units), Siemens VDO Automotive  (instrument clusters) and Valeo Climate Control de Mexico (air conditioners).

Engines are produced at BMW and Magna Steyr plants in Munich. Magna Steyr made 1 million engines in 2012 including both 4-cyl. and V-6 diesel mills, as well 6-cyl. gasoline engines. Included in the total are 700,000 diesels. The Munich factory provides a motorsport engine.

BMW launched diesel cars in the U.S. in 2007 and currently sells diesel versions of the X5, X3 and X5 being produced in South Carolina. Diesel-powered 3-Series and 5-Series cars will be added to its U.S. lineup.

Transmissions mostly are imported from ZF Friedrichshafen in Germany, although the supplier opened its first U.S. plant in Gray Court, SC, last month. The facility, which builds 8-speed and 9-speed automatics, has capacity to produce 1.2 million units.

BMW has not announced whether it will source transmissions from the U.S. plant. That’s the expectation, although the new X5, which officially went into production Aug.1, uses an imported gearbox.

BMW ships some 700 cars daily from the plant by rail mostly to the port of Charleston. Norfolk Southern is the rail operator.