Spring change.

Auto seat maker Porter Engineered Systems improved reliability of a seat back adjuster by switching to wrap springs from Reell Precision Manufacturing Corp. of St. Paul, Minn. The move saved money by reducing the number of parts scrapped for faulty actuation.

It was the precision of

the Reell manufacturing method that made the difference. Manufacturers usually sort wrap springs by tolerance once they are made, but the Reell process builds the tolerance into the part. That was a key step for Porter because the two wrap springs it uses in each adjuster must release their grip on a shaft at exactly the same time. Release is controlled by a single lever.

A manufacturing engineer at Porter in Westfield, Ind., said the springs can be tested only after they're assembled onto fine seat-back mechanism. If the springs don't release in unison, then the whole assembly must be scrapped.

Reell vice president Rob Jackson attributes the tight tolerances that his company holds on its wrap springs to a special manufacturing method. By closely monitoring its winding machine and adjusting it continually as the spring is made, Reell has helped Porter to reduce its rejection rate by 30 percent.

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