Efficiency, Variety And Quality–keys At webasto

Although some may consider sunroofs commodities, at the Webasto plant in Utting, Germany, that word is eclipsed by "variety," "productivity," and "quality." Just look at the facts.

The plant employs 354 production workers and 19 apprentices, and this group productively produces an array of products. Specifically, on a daily basis, the shipping dock at the 12,200-m2 assembly plant receives:


  • 200 outer-slide roofs for DaimlerChrysler.
  • 1,150 glass sliding roofs for DaimlerChrysler.
  • 80 "Lamella" (multi-pane tilt-slide) sunroofs for DaimlerChrysler.
  • 2 large module glass roofs for Maybach.
  • 135 convertible tops for SMART.
  • 1,500 glass sunroofs for VW.
  • 50 moveable rear spoilers for VW.
  • 280 powered side "flaps" for the VW Beetle Cabrio.
  • 150 powered rear spoilers for Porsche.


The variety continues in terms of customer-specific requirements. For example, the VW Group wants the seal on the sunroof itself, while DaimlerChrysler insists that it be placed on the vehicle. Then there's the variation that happens within corporations. According to Franz Lindinger, operational unit manager at the Utting facility, "DaimlerChrysler's Bremen plant wants the roofs delivered upside down because they are manually inserted into the vehicle, while the Sindelfingen plant wants them shipped right-side-up because they are robotically inserted."

Then there's the quality side of the coin. Although some might think of a sunroof as nothing more than a piece of glass that slides up, down, fore and aft, there often is much more to it than that. Take the Mercedes E-Class, which offers an integral solar panel and a silver UV-blocking foil embedded in the transparent section of the glass. According to Lindinger, dust infiltration during the encapsulation process–that point at which the seals are added–produced "stars" along the sealed edge when viewed from the outside. Approximately 70% of the E-Class sunroofs had to be scrapped when Webasto started production, a number which has fallen to less than 1.5%.

The encapsulation takes place in a two-piece die set in which the glass is inserted upside down in the lower half, and the steel support frame is placed in the upper half of the die set. An internal measuring system makes certain both pieces are centered, and a low-velocity air jet removes any dust before the die is closed and rubber injected to seal the assembly. The completed part is placed in a rack and travels just a few feet–Webasto is interested in productivity, so there's no wasted travel–to another station where the glass is polished and the flashing removed, and the opening panel is fitted to the rest of the sunroof assembly.

Productivity also is enhanced when the OEM is a believer in component commonality. The sunroofs for the VW Phaeton, Bentley Continental GT and Audi A8 are the same except for their interior sunshades. Another more extreme example of commonality extends to the moveable rear spoiler Webasto makes for VW's Beetle: the same mechanism is used to activate the spoiler of the Bentley Continental GT. But the ultimate commonality comes from Webasto itself. The aluminum side rail extrusions on every sunroof have the same cross section, and are delivered to Utting in 10- to 15-meter lengths. "These pieces are stretched approximately one more meter to give them the proper profile," says Lindinger, "before they are drilled and cut as needed for the application." Finally, the aluminum extrusions used throughout the Utting facility to frame the fixtures and assembly areas at the Utting facility are framed with a common star-shaped cross section extrusion. This reduces the amount of change required to alter production cells, which also increases productivity by reducing downtime.

Developing a Sunroof—Without a Prototype Vehicle

A sunroof is a fairly significant part of any new vehicle program (imagine the consequences if it didn't seal properly), yet they often enter development long before the OEM is willing to release a prototype vehicle to Webasto. "The OEMs can't afford to release an early testing prototype to us just for sunroof testing," says Webasto's Franz Lindinger, "so we must improvise with a technically correct package until we can gain access to the actual vehicle."

For example, a full-length panoramic sunroof for a future high-performance SUV was mounted in a base that mimicked the curvature of that vehicle, and fitted to a Mercedes passenger van. Close in size to the target vehicle, the Mercedes van allowed Webasto engineers to test the unit without disrupting the OEM's test schedule. An important point when you realize that the average sunroof takes a minimum of one year to design and develop.