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MINI Factory, Monster Mechanics

Historic MINI factory relies on robotics

OXFORD, England — When BMW decided to revive the MINI in modern form, after buying the old Rover company, they needed a factory that could handle the task. What better choice than the facility on the outskirts of Oxford, where original Minis were produced from 1959 into the beginning of the 21st century.

M-Robot

MINIs are manufactured in three buildings at the sprawling 112-acre facility, located on the Oxford Ring Road at Cowley. As you walk into the first one and look around, an eerie sensation takes over. Where are the workers? There's plenty of typical factory noise, but few people visible. In the next building, it turns out, assembly workers are engaged in the usual tasks of an auto manufacturing company. Through the first stages, however, robots basically do all the work.

A total of 256 robots are on-site in this "body-in-white" area. Here, you find "more robots than people," said John Strange, who's worked at the Oxford factory since 1962 and conducted this tour for a single visitor.

Because BMW is the parent of the MINI operation, comparisons are often made to the German automaker's factory operations. Obviously, they want the MINI to gain a reputation for quality comparable to that of BMW models. BMW's factory in Spartanburg, South Carolina uses considerable automation, yet it doesn't give off the weird sensation that robots are in charge.

"Body in white" is the term used to describe the unfinished basic car body, before it's painted or has any components installed. The underframe goes through a series of preliminary steps, before it's ready to move into Framing areas 1 and 2. "One of the key features of body-in-white is measurement," Strange said. The body "must be accurate before it goes to the assembly hall."

Human Factor

Like other manufacturers, MINI uses Perceptron equipment to confirm dimensions electronically. The underframe moves through five measuring stages, to make sure everything is within limits. "Automation is 100 percent on welding," Strange explained. They might not need tea breaks, but the welding robots need to be replenished in other ways. Workers stop every two hours to change welding caps.

Human employees, known at MINI as associates, must "keep lots of spares for the robots," Strange said, because they require extensive maintenance. Six-axis robot heads aren't easy to change, either. There's a "four-hour window each day" for maintenance: from 2:30 to 6:30, plus time on weekends.

How many imperfections are found? System efficiency is 88 percent, Strange said. "That's no secret."

Body panels arrive from BMW Swindon, which is a separate facility. One in four of the MINIs produced at Oxford is a convertible. Unlike the saloon (sedan), which relies on its pillars, the convertible's "strength is in the underframe," Strange said. The MINI convertible is 100 kilograms heavier.

Some brazing is done, at the waistline, for small sections that are subject to flexing and are beyond the reach of a robot. After the developing MINIs have left Framing 2, they're positioned on body bars. They "sit on those through the system," Strange said. Only a handful of robots can be found in the Assembly Building. At one point on the assembly line, the powertrain/frame is wedded to the body, using two robots to tighten them together.

The Chosen

Petrol (gasoline) engines come from Brazil, while diesels are made in Japan. Gearboxes hail from Germany.

Bodies are painted in a separate building. Doors are fitted and painted, and then removed before additional work is done. Farther along the line, each door "comes in on an assister," Strange said, fully trimmed with all hardware installed.

Glazing of the windshield is done by a robot. Expanding "biscuits" are inserted into panels to absorb noise. Cardboard is used as gusseting for the saloon's roof, because it's cheap, efficient and environmentally friendly. Two pieces are inserted automatically, after glue is applied by a robot. Ergonomic aids help ease the assembly associates' tasks. All tools are electric, not air-powered.

One randomly selected body per day goes to the "Wenzel room" for a 1500-point check, independent of the Perceptron system. On the final line, Strange noted, associates are "checking the details, checking the gaps ... what the customer wants." If a problem is discovered before painting, the car goes to the Rectification Area. Some 600 bodies are typically on hand. Planners need to keep the "bank full," Strange said.

Shift Business

Customization is critical. MINI customers often spend 2,000 pounds ($3,000) on extra-cost items, said corporate communications manager Alexandra Brooks. A head-up instrument display will join that list later, Strange noted. There are 365 options for the wiring loom, "all bespoke to the car" and made by girls in Romania, Brooks added.

Half of the completed MINIs are shipped by rail and half by truck, without delay. Freight cars are waiting right outside the door. Altogether, it takes 24 hours to build a MINI. One out of 10 MINIs is test-driven before shipment, and 10 percent must pass a water-ingress test. MINIs leave the factory at a rate of 38 units per hour, 500 to 600 per day.

Two shifts have been operating: from 6:30 a.m. to 4:30, and from 4:30 to 2:30 a.m. Associates go back and forth between the two, and many couples who are employed here work different shifts. "Weekenders" work Friday to Sunday.

About 4,500 employees work at MINI, including 1,300 temps on the second shift and weekends. More than 100 apprentices are employed, and workers average 37.5 hours a week. For training purposes, mobile classrooms come to the associates.

MINI Parts

More than 3,000 parts for the MINI are provided by 200 suppliers (119 of them in the U.K.). The dashboard is the largest component that comes from an outside supplier.

Unlike most factories, the MINI facility has a dress code for visitors, who are obliged to wear specially-colored jackets. Supplier observers are sometimes on-site, as are independent auditors, who wear distinctive red coats.

William Morris built his first car at Oxford, a two-passenger Morris Nine, in 1913. A row of historic photos demonstrates that today's facility is actually far smaller than it was in the '50s. When the Cowley plant was turning out a broad range of memorable models, including Morris Minors, about 24,000 people were employed. "In the '60s, '70s you couldn't hear anything with this noise," Strange said. Now, the sounds are more tolerable.

Today, MINI buyers in the U.S. can choose the 115-horsepower Cooper or 168-horsepower Cooper S. In the U.K. and elsewhere, a MINI One with a 90-horsepower petrol engine went on sale in July 2004. The MINI One D (diesel) debuted a year earlier.