Highly-Automated Mexican
Producer of Automotive Body
Panels Relies on Servo-Controlled
Coil Feeding to Support Quality
Mandates and JIT Operations

One of 24 stamping facilities operated by components supplier Oxford Automotive (Troy , MI), the 330,000 sq. ft. plant in Ramos Arizpe, Mexico has a unique distinction: it is the first Mexican facility to produce aluminum hoods with a class A surface finish. The state-of-the art, QS 9000 certified plant produces various body panels (doors, hoods, lift gates), as well as rear and underbody components, for the Pontiac Aztek and Buick Rendezvous models assembled at nearby GM Ramos. There are other customers also, including OEM and Tier 1 suppliers. Over 60 part handling and welding robots, and 38 stamping presses, assist 611 employees in round-the-clock operations.

Key to today's critical automotive fit and finish expectations is precise handling of the material, from coil to completed part. At Oxford, quality assurance is complimented by a commitment to production efficiency, including the flexibility to run a variety of parts with fast changeover response to meet Just-in-Time delivery requirements. Automation is seen as a tool for achieving uptime and scrap reduction goals.

500 to 1000-ton Verson presses, for instance, run a mix of progressive and single-hit dies, and are also used for blanking operations to produce blanks that are stamped on other presses. Wide, medium and narrow width coils are fed to the presses by coil reels, power straighteners, and servo roll feeds supplied by Coe Press Equipment (Sterling Heights, MI).

A full compliment of automation "assists" minimize coil changeover downtime and part changeover time on two 30-inch and three 72-inch width capacity press lines. Frequency of changeover on these lines is high, ranging from 35 to 60 changeovers per week. Adjustments for widths must be fast and simple, since coil width variation is as much as 61 inches (11 inch to 72 inch range) on one of the largest capacity press lines. The 30-inch press lines run the thickest material, processing a range of 1.0 mm to 3.5mm steel and aluminum.

Vee-deck style coil cars, integrated with the traveling coil reels, are used to cradle incoming coils, keeping them close to the reels so that they can be mounted quickly when coil is depleted or removed due to part changeover. Peeler/threader/hold-down units also simplify and speed up the coil changeover process. The powered coil straighteners pull the coil off the reel, using seven polished chrome straightening rolls that prevent marking that would affect surface finish quality.

A threading table, with adjustable passline, rises to guide coil over the loop area during changeover. Coil is fed into each of the five presses by Coe servo roll feeds equipped with ServoMaster controls. On one of the 72-inch lines, up to 12-foot lengths of coil are fed at 240 ft/min through the Coe CPRF-672 servo feed, to allow stamping of large parts at 16 spm (strokes per minute). Feed speeds of up to 365 ft/min are possible on the 30-inch lines, with feed accuracies of up to +/-.003".

The servo control allows the width and thickness changeovers to occur without the need for time-consuming trial-and-error adjustments, a big downtime-reducing factor in this JIT environment. "Embracing the concept of lean manufacturing is a key element of continuous improvement," said Engineering Manager Fabian Velazquez . "Customers are asking for JIT deliveries, with only 4 hours of inventory, on average. At times, we'd like to carry 20-32 hours of inventory, but our customers always push us to go lean."

The birth of this impressive facility two years ago was one for the record books. Velazquez explains: The Coe equipment was delivered very quickly to meet our aggressive timing demands. Our goal was to be up and running in less than a year. It took our combined US and Mexican teams to meet this goal—and to achieve the full roll out in 18 months." The pace of expansion, with a focus on advanced automation, has continued during 2001 at Oxford. Their newest tandem line consists of five 1,500-ton presses that are configured with ISI Pathfinder between-press transfer units, as well as blank destacking equipment from Atlas Technologies.

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