Mold coating solves PC glazing problemMold coating solves PC glazing problem

It’s everyone’s nightmare—parts that stick to the mold. But when mold-release sprays just won’t solve the problem, the time comes to coat the tool. For the mold that produces polycarbonate rear windows in the MCC Smart Car, chromium nitrite coating proved to be the answer.

Polycarbonate glazing products are just beginning to appear in vehicles, and the colorful Smart is one of the first to use molded windows. The tool consists of a highly polished surface (almost optical in quality), which presented a problem for typically sticky polycarbonate. To complicate matters, the windows were a two-shot molding, with a black overmolded border framing the clear window.

Moldmaker Scheffenacker uncovered the problem when trialing the molds. Balzers Ltd. (Liechtenstein) offered several options from its Balinit coatings line, finally settling on a chromium nitrite (CrN) to solve the problem.

Balzers has been involved with wear-resistant coatings since the 1970s. Its wear protection unit has 38 centers worldwide that offer contract coating services. According to Rainer Wild, product manager for wear protection, the annual cost attributable to tool wear is staggering. "Machine downtime, defective products, and expensive repair and maintenance work hold down productivity and drive up costs," he says.