A factory worker drives a forklift carrying a four-ton metal casting across a polished concrete floor. Surrounded by looming robotic equipment, he’s the only human in sight at DMG Mori Seiki’s gleaming machine-tool plant in Northern California.

Three rows of towering, growling machines carve out precision components from rough metal castings weighing anywhere from a few pounds to a few tons. It’s the kind of almost-deserted vista you would expect in advanced manufacturing.

This is the plant’s automated half, but on the other side of a wall with windows, assembly lines swarm with people in white helmets and navy uniforms. There, 40 workers build bedroom-size machines by hand, assembling 2,000 parts to create the computer-driven instruments that will form the hearts of auto, aircraft, and electronics factories across America.

The Japanese call them “mother machines,” because they make other machines possible. Also known as milling machines, they use spinning tools to carve complex shapes out of roughly cast pieces of metal. The results include molds for die casting, gears for transmissions, and cases for smartphones.

The Davis factory builds some of the most advanced computer-numeric-controlled (CNC) milling machines in the world. Fast, durable, and accurate to the micrometer, they are able to move both the cutting devices and the parts they’re shaping in multiple directions. Manufacturers can use DMG Mori tools to make more products, make them faster, and use less energy over longer periods of time.

The quality and productivity of the Davis machines put them “at the upper end of the industry,” says David ­Dornfeld, chair of the mechanical engineering department at the University of California, Berkeley.

DMG Mori’s decision to build the $50 million factory in Davis says important things about the future of U.S. manufacturing, according to Dornfeld. As automation makes labor costs less important, producers of everything from smartphones to artificial knees to electric cars are increasingly able to choose local production, he says.

Among the key advantages of locating in California: the factory is closer to customers—not trivial when shipping products that weigh tens of thousands of pounds—and to the company’s innovation center and local university research partners. Building some of its machines in the United States also insulates the company from losses on currency exchange and has helped to improve its sales, profits, and share of the U.S. market. The United States now accounts for 25 percent of DMG Mori’s global sales.

The tidy white-and-gray DMG Mori plant sits unobtrusively next to Interstate 80. Flatbed trucks carrying its 20,000-to-40,000-pound products can take the road west to Silicon Valley or east to auto, aircraft, and oilfield-equipment factories. A map in the assembly hall sprouts tiny white, yellow, navy, and orange flags representing the products’ destinations.

The factory grew out of a relationship between the company and the engineering school at the University of California, Davis, according to Zachary Piner, general manager of the plant’s technology department. The company established its Digital Technology Laboratory in Davis in 2000. Piner and the factory’s managing director, Adam Hansel, were completing graduate degrees when they were hired as two of the first four employees.

“For this combination of software, hardware, and precision manufacturing, companies need proximity to educational infrastructure,” says Enrique Lavernia, the dean of the Davis engineering school. “This high-value manufacturing of sophisticated technology is an opportunity for us in this country.”

One reason for placing the factory on the same site was to capitalize on this talent, Hansel says. With more than 60 engineers, the center designs machine tools and software for DMG Mori worldwide. One smartphone app they designed enables customers to monitor their machines, displaying red, yellow, and green lights next to tiny images of the devices to show their operating status.

The laboratory’s engineers also helped design and set up the factory itself, inventing fixtures for use in product assembly and developing software for the automated lines. Now the laboratory uses the factory to test next-generation prototypes.

Inside the plant, steel-reinforced floors are 40 inches thick to prevent vibrations. The air is almost odorless and free of dust, an enemy of precision and a safety hazard as well. There’s so little noise that people can converse without raising their voices.

Two workers operate a crane to load castings onto the machining system. Six hours later, the parts emerge with precise grooves, tracks, threaded bolt holes, and other shapes carved into them. A system designed by the Digital Technology Laboratory uses yellow robotic arms to vacuum up metal shavings and chips.

Machines verify quality at every step. As parts enter the assembly hall, they go through a $1 million coördinate-­measuring station that’s accurate to within four micrometers.

The factory goes months without a quality problem, Hansel says. Half of the factory’s products go to small parts-making shops with 50 workers or fewer. They can’t afford malfunctions on machines that anchor their production and cost $120,000 to $500,000. White-shirted quality-­assurance workers conduct 100 hours of rigorous tests at various stages of assembly, Hansel says.

Starting with the foundation casting, workers attach major subassemblies that hold the moving parts. They add electrical controls and wiring, hydraulic pumps and piping, and sheet-metal covers. From start to finish, the whole process takes 14 days. There are usually 30 machines under construction at a time.

On one machine, Jeff Gagne installs a shiny rotary table machined on the other side of the plant. He connects the electrical controls and uses sensors to verify that the table is square to the machine’s spindle, which spins cutting tools.

Like the other assemblers, Gagne rolls a cart with a rack of hand tools from machine to machine. There are torque wrenches, box-end wrenches, socket wrenches, and Allen wrenches. Small abrasive stones that can shave off tiny layers of metal are there, too. “About 20 strokes will remove a micron,” Hansel says. “There’s an art to it.”

The DMG Mori plant has about the right balance between automation and assembly by hand, UC Berkeley’s David Dornfeld believes.

“It would be crazy to try to build a machine tool with robots,” he says. “This is instrument-making, and each machine does have its own personality.”