(FORTUNE Magazine) – Amassive cage sits tucked in the back of Hydro Automotive Structures' aluminum-extrusion plant in Holland, Mich. On first glance the apparatus looks about as clunky as any shop-floor machine tool. But look more closely and you'll see a multilegged red creature thrashing wildly, its big beak piercing aluminum windshield frames at a rapid clip. This metal-cutting beast, known as the Tricept, is working on the windshield frame of a Cadillac XLR Roadster. It drills and mills 107 holes and slots in just ten minutes, leaving mounds of tinsel-like shavings in its wake.

By combining the flexibility of a robot with the power of heavy machine tools, the Tricept is changing the way metal is cut. It can reach around corners and drill bumpers or shave composites off airplane wings--faster and more cheaply and accurately than some of the conventional tools it replaces. "It lives in between where robots leave off and where machining centers take over," says Paul Sheldon, a Milwaukee manufacturing industry inventor and consultant.

The Tricept's novel design is what lets it inhabit this middle ground. Inventor Karl-Erik Neumann gave the device a center tube--an extra leg--that serves as a stabilizer while its three active legs position its tools for cutting or drilling. The arrangement enables the Tricept to bring much more force to the task at hand than simple robot designs.

The machines are made by Sweden's SMT Tricept and cost between $300,000 and $1 million apiece. That makes them a tough sell in today's depressed machine-tool market. But big names in the aerospace and automotive industries have been putting in orders. Hydro uses 15 of the machines at the Michigan factory; Boeing uses several to drill holes in landing gear, floor beams, and wings; and General Motors has just purchased two Tricepts.

Tricept's flexibility helps sell it. For one thing, it can maneuver fluidly around a part, machining multiple areas. Perhaps more important, it can adapt quickly to different jobs. That's crucial to manufacturers that are turning out cars or planes in smaller and smaller batches. Kenneth Duty, a numerical control programmer at Boeing's Wichita factory, uses the Tricept on several airplane models. With conventional machine tools, switching from one model to another used to take a month, he says. With the Tricept he can do it in days.