In the auto industry, changes in manufacturing processes are difficult. Material certification processes can be long and expensive, especially for parts designed to comply with government safety regulations. But when Quadrant CMS (Tielt, Belgium) recently introduced a thermoplastic composite that dramatically reduced airbag container cost, no re-certification was required.
Eight years ago, Quadrant helped pioneer polyamide (Nylon) 6.6 with 30 percent glass loading for use in molded steering column airbag containers, which hold the uninflated bag and gas generator used to inflate it. The molder developed one of the first large-volume, composite-for-metal replacements for the part, on the 1996 Ford Focus. Today, 30 percent glass Nylon 6.6 is the material of choice for this part for several automakers, based on its significantly lower weight and cost, compared to previous steel and magnesium designs. But Quadrant's Ivan Meersman points out, "There is always a cost pressure, so automakers were looking for a cheaper solution." The answer was a toughened (rubber-modified) Nylon 6 with 40 percent glass, supplied by DSM Composite Resins AG (Schaffhausen, Switzerland) and DuPont Nylon Intermediates & Specialties (Bad Homburg, Germany). "Nylon 6.6, in general, has better mechanical and thermal properties," Meersman explains. "But tests have shown that the Nylon 6 duplicates pretty much the performance, with 15 to 20 percent savings in part cost."
The first Nylon 6 for 6.6 replacement was for the Renault Laguna. The Nylon 6 parts can be injection molded in the same matched, hardened steel molds used for the Nylon 6.6. With fiber length of only a few hundredths of a millimeter, the increased reinforcement load poses no mold-flow problems during injection, which takes just 30 seconds. "We make a slight modification in the molding parameters, but other than that, it's fairly a 'drop-in.'" Meersman maintains. "You'll notice a slight difference in part dimensions or other parameters, but most of the time, you can simply replace the material. But in the end, the design of the part is an important factor in judging whether Nylon 6 or 6.6 is the preferred option."
Since then, Quadrant has completed or initiated the switch for airbag containers on several other airbag products.