ISOlating test standards

Everyone's talking about how automakers and suppliers are consolidating parts and standardizing quality standards to streamline operations and control costs, but there's more to the story -- way more.

Think of the number of different kinds of materials that go into a vehicle and assume that each automaker has different measurements and methods it wants suppliers to use. It's easy to imagine how much money could be saved by standardization, so understandably U.S. automakers and their plastic resin suppliers are moving quickly in that direction.

An early 1996 letter from the United States Council on Automotive Research (OSCAR) consortium to all Big Three thermoplastic material suppliers advises that by June 1, 1998, all material specifications will be converted to International Organization for Standardization/International Electrotechnical Organization (ISO/IEC) test methods.

Most nylon resins were converted in January 1996, followed by polybutylene terephthalates (PBTs) and polyethylene terephthalate (PETs) in June. By June next year, acrylonitrile-butadiene-styrenes (ABS) and acrylatestyrene-acrylonitriles (ASA) resins are scheduled to adopt the standards, with other automotive plastics converting by June 1998.

"It comes down to economics," explains Ranganath K. Shastri, a development leader at Dow Chemical Co. "In order to remain competitive, we have to be able to provide all the (testing) services at the lowest cost possible."

Each of the Big Three has different standards for testing the same properties of the same material, he says. And because each supplier tests differently, automakers don't trust the results and they do their own testing. "There are now 20,000 grades (of resin) out there," Mr. Shastri observes, and "you have to have a way to make an apples-to-apples comparison."

At least initially, he says, standardization will be more costly as suppliers purchase new equipment and perform tests both the old way and the new way.

"It'll cost more as the transition is made," he explains. "We have to show people both sets of numbers for awhile to build confidence in the new system. The people who buy resin from us have to be comfortable that the material has not changed."

Over the long run the cost of testing will come down, he says, citing a report by DuPont in Germany that claims a 50% savings in testing after converting to ISO standards.

"OEMs, on the other hand, will be able to trust the data and not have to retest the material," says Mr. Shastri. "And if everyone is talking the same language, the data is comparable."

The cost increase during what is expected to be a tree or four-year transition period will include double testing and one-time charges for a new test mold to create the small, dogbone-shaped test specimen ($10,000-$15,000) and possibly an up-to-spec 50- or 80-ton injection-molding machine ($50,000). Other costs likely will include modification of physical testing equipment and training technicians.

One reason for standardization is that automakers, suppliers and 26 other regional and national authorities worldwide require varied test specimen preparation and dimensions when testing the measurement of thickness-dependent properties such as impact strength, heat-deflection temperature and flexural properties.

ISO 3167 requires the use of a balanced, two-cavity mold with a defined gate design to prepare test specimens used to measure the properties of plastic materials. Identical cavities with large gates and a balanced runner system will fill and pack the mold consistently, minimize shear effects and produce uniform specimens.

By using ISO standards, testspecimen dimensions, process parameters and the injectionmolding machines used remain the same and therefore test results will be uniform, resulting in a fair and accurate comparison of materials.