In an industry increasingly obsessed with cutting curb weights, Audi’s two assembly lines for aluminum cars in Neckarsulm, Germany, are at the spear tip. No other automaker has pursued aluminum body construction as doggedly as Volkswagen’s upscale subsidiary, which assembles the R8 mid-engine supercar and A8 luxury-liner here from aluminum alloy and has operated a lightweight development center since 1982 devoted largely to lucky number 13 on the periodic table. A highly enlightening day spent walking these two lines proves that lightweight materials carry a lot of weight at Audi.

Lying along the Neckar River in southwest Germany, Neckarsulm is about an hour’s drive south of the country’s financial hub in Frankfurt. It owes much of its livelihood to Audi Aktiengesellschaft and the many local suppliers that feed it. A hand-me-down from when Volkswagen absorbed the car and motorcycle maker NSU in 1969, it was home to the rotary-powered NSU Ro80 of 1967–1977, and some 330,000 Porsche 924s and 944s also emerged from its gates. The plant currently employs 13,630 people on a campus that is almost two miles long and a half-mile wide. Besides the R8 and A8, its various lines currently zip together A4s, A5 cabriolets, and A6s. It will also be home to the forthcoming A7 four-door coupe.

The R8 and A8 lines are a study in contrasts. Just 17 R8 bodies per day roll out of the small welding hall where 49 men and 1 woman (her name is “Sandra, I think,” said our guide) plus eight robots weld, rivet, and bolt up the R8’s aluminum space frame. Next door, another 100 workers perform final assembly on the R8 shells after they emerge from the paint shop.

Over on the A8 line, which is 80-percent automated, 300 robots weld up the big space frame at the relatively frenetic rate of 87 cars per day. That’s actually a tiny number—I was once in a Ford plant that slammed out 66 Tauruses per hour—but compared to the R8 line, the level of noise and activity on the A8 line is, at first, startling, and orders of magnitude greater.

Here’s how an R8 is born: the front, middle, and rear sections of the space frame are first welded up as separate modules, mostly from aluminum extrusions and sheets but with a few strategically placed and incredibly complex die-castings serving as joining nodes, much like the wood wheels do in an old Tinkertoy set.

The blue haze, popping, and sparks are from the metal inert gas (MIG) welding guns held by the workers. The only automated operation is the insertion of 308 “flow drill screws” into the R8’s floor and cabin walls. These small, spike-tipped, self-tapping screws are spun in at such high speed that they flash-melt the aluminum into creating an elongated threaded shank on the back side, which adds greatly to the pull-strength.

At various points, the sub assemblies and fully assembled frames are inserted into booths where laser alignment rigs check the accuracy. Rarely do you see the actual movement of the line—each frame sits at a welding station for up to 30 minutes before moving on, a veritable eternity in the car business. It takes two working days to complete a frame and clad it with exterior panels, four days to get it painted and cured, and another two days to complete the final assembly.

Naked R8 shells fresh from the paint shop sit outside on huge racks bagged in plastic. Look close and you’ll also see a few Lamborghini Gallardo shells. The Gallardo’s body—an older and somewhat different aluminum-space-frame design from the R8—are assembled at a nearby supplier, but Neckarsulm’s paint shop paints them before shipment to Lamborghini’s factory in Sant’ Agata, Italy.

When the R8s are ready for assembly, they move inside and then sit for two hours to come up to room temperature. There are 17 steps on the assembly line, which operates under a “supermarket” parts-feed system. Each shell has a coded build sheet listing the colors and equipment options. When a new shell rolls up, one or two workers from each station leave the line and go into an adjacent area where parts are stored on racks. They pull the needed bits from the racks and put them on carts to wheel back to the line. It’s a slow, careful process, but with a half-hour to get the job done, nobody rushes. The workers move in a deliberate, efficient manner but take their time.

We were stripped of cameras before leaving the lobby, and there’s a reason the few company-issued photos accompanying this story are of the R8 line and none are of the A8 line. The A8’s much faster and more automated assembly is far more modern and complex—and potentially more interesting to Audi’s competitors.

Most of the A8’s automated body assembly happens behind opaque spark curtains. Towering, thickly armed robots pick up, move, and spin the various subassemblies through the air as if they’re made of paper and in seamless ballets of machinery. As in pretty much all modern, high-volume car plants, the welding of the A8’s floor pan and body sides is done in one booth densely packed by a surgical team of giant robots and their associated brambles of wires and plumbing.

On the A8, just a few short welds are done by hand, always in little crannies where robot arms can’t reach. One technical leap Audi is very proud of in the A8 is a single, 4.6-foot-long, thin-wall die-casting which stretches from the rear cabin to the trunk. There are two of these castings in the floor of each A8. They are highly complex parts doing the duties of many by serving as most of the rear support and crash structure as well as the rear suspension perches. Audi says it has taken 28 years of development to realize these die castings.

Whereas an R8 sits for 30 minutes, an A8 reposes for just six minutes at each station, moving through the body shop, paint shop, and final assembly plant in about six days. The A8’s final assembly is much longer owing to the car’s greater complexity, and the line snakes back and forth through the hall. Parts feed to the line using a far more common “kanban” system of baskets on racks that are refreshed by dedicated re-supply workers—basically the lean, highly organized system pioneered by Toyota. When our group moved through, a few of the previous-generation A8s were still moving down the line, thanks in part to a last-minute 1400-car order from China for the old model.

Like the R8, each completed A8 is subjected to a 30-mile test on Neckarsulm’s roads before shipment.

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