Fixing Fixtures

No one involved in a vehicle program benefits when it flops in the marketplace.

Nobody, that is, except perhaps tooling suppliers that win new business when an auto maker decides an emergency redesign is necessary.

One tooling supplier, Tesco Measurement Solutions, is in the unique position of helping auto makers reduce tooling costs with a new technology that eliminates the hard fixtures that have been used for decades to check the dimensional accuracy of parts produced with that tooling.

A division of Japan's Hirotec Worldwide, Tesco has supplied flexible body-in-white (BIW) assembly manufacturing tooling since 1989. Tesco produces hemming presses and hemming dies for closure panels (doors, hoods and decklids).

In 2003, at the urging of General Motors Corp., Tesco joined with CogniTens Inc., a company founded in Israel in 1995 that specializes in 3D non-contact measurement equipment. Until that time, Tesco had been producing traditional coordinate measuring machines.

Together, Tesco and CogniTens began developing a measurement system specifically tuned to the needs of automotive BIW assemblies.

The result is the I3 Measurement Cell, which uses CogniTens' OptiCell 3D non-contact measuring technology in cell configurations that Tesco says are “100% compatible with OEM plant requirements.” I3 stands for Industrialized Image Information.

Tesco says it designed the cells to reduce auto makers' cost for developing, proving out and monitoring expensive product-specific tooling.

The I3 system is new to the market and is winning significant buy-in from General Motors, which has purchased eight cells since July 2005, says Gary Krus, vice president-measuring systems at Tesco.

As of mid-March, Tesco was assembling a ninth cell for GM, and a tenth was to be delivered to the No.1 auto maker later this year.

As GM warms to the I3 system, it has abandoned the use of hard checking fixtures altogether for certain vehicle programs.

Krus says GM used extensively the I3 approach to evaluate fit and finish for the interior and exterior of the Pontiac Solstice roadster and the all-new Chevrolet Tahoe SUV, which is the first vehicle to launch from the massive new GMT900 fullsize truck platform.

The fully automated I3 equipment typically is used for problem solving during launch, as a vehicle program is ramping up to high volume.

In addition, GM is using Tesco equipment at die shops to test certain dies. Once the equipment confirms the die is doing its job correctly — based on imported computer-aided design (CAD) data for the panel being evaluated — GM approves payment to the die shop.

When the dies are moved to their “home” vehicle assembly plant, the measurement cell moves to the plant as well, where it is used for part sampling, Krus says.

Checking fixtures are common in stamping and vehicle assembly plants. Costing up to $200,000 apiece, a checking fixture is like a large picture frame, custom crafted with precision to hold a closure panel after it has been stamped and hemmed.

Once the panel has been mounted in the fixture, a quality-control staffer takes dozens of measurements to ensure the panel will fit properly when it is installed on the vehicle assembly line. Every vehicle's hood, door and decklid has its own checking fixture.

This manual system is not a panacea, however. Sometimes, costly fit-and-finish problems are not detected until late in a program.

The I3 system is fully automated for repeatability and high throughput. A robot-mounted optical head with three charge-coupled device cameras uses a white light pattern to capture up to 1 million surface images in less than 1 millisecond.

The information gathered is delivered to the operator in a user-friendly color map that pinpoints areas of dimensional inaccuracy.

“Typically, production metal for a closure panel never meets up with the CAD data 100% of the time,” Krus says. “But you can match it electronically.”

CogniTens developed the camera technology and software in Israel specifically to help the auto industry shorten development times.

The business case for I3 is compelling. Twelve conventional checking fixtures for right and left inner and outer doors and bodyside panels would cost an auto maker $1.6 million, Krus says.

A robotic I3 cell, which can measure all 12 panels, costs $600,000, plus $80,000 for software; $30,000 for installation; $170,000 for training, support and other expenses; and $500,000 for holding fixtures. The total price is $1.38 million.

The biggest savings, however, arrive when the I3 cell is reprogrammed and reconfigured for a new model launch.

“You will see cost savings of 46% for all new models,” Krus says.

A conventional checking fixture, on the other hand, is not recyclable. It is custom made and scrapped once it has fulfilled its job. A new vehicle program requires a new checking fixture, adding cost to the bottom line.

Although checking fixtures have been used for years, the industry is beginning to migrate to computer-controlled devices.

A Tesco competitor, Perceptron Inc., has been marketing its Flexible Ring Gauge, a scanning device that uses a closure panel's CAD model to project a “virtual gauge” over the panel to replicate the body opening with which it mates (see WAW — Jan. '05, p.25).

A digital non-contact scanner mounted to a robot takes 1 million measurements with the Perceptron system, checking gaps and body flushness, within four minutes.

In addition to the I3 system, which is a fixed cell, Tesco and CogniTens also sell a portable Optigo 200 scanner that runs on the same basic software as the I3 cell. The Optigo 200, however, is not automated, and the scanner must be used manually.

By way of comparison, one customer had used a coordinate measurement machine with a laser scanner for competitive-vehicle analysis. “The process would take two weeks,” Krus says. “They have purchased this portable system, and now they are doing that work in 50% of the time.”

Tesco's relationship with GM began in the late 1980s, when the auto maker recruited its tooling expertise for body panels.

Today, Tesco tooling produces the hems for all of GM North America's closure panels. In the past 10 years, Tesco has installed 400 hemming presses for closure panels in GM North America facilities.

In China, Tesco also supplies tooling for doors to GM for its Shanghai vehicle assembly operations.

About half of Tesco's sales in North America are to GM. The second largest customer is the Chrysler Group (34% of sales). Sales to Tier 1 suppliers make up about 11% of revenues.

GM is not the only domestic auto maker interested in Tesco's system. Krus says Ford Motor Co. is conducting trials with the I3 cell for stamping operations.