Case Study: Dimensional stability, low-warp properties and abrasion resistance were the main reasons DuPont™ Crastin® LW9020 thermoplastic polyester was chosen for sunroof frame sections on BMW’s Series 1 and 3 models.
Webasto Elects DuPont™ Crastin® for BMW Sunroof Frame
Application Description
The front section of the frame for the sunroof on BMW’s Series 1 & 3 models is made of DuPont™ Crastin® LW9020 thermoplastic polyester. The 1 metre long injection-moulded part weighs only 0,87 kg thanks to its strengthened walls that are 2,5 mm thick.
Benefits Gained
High stiffness, strength and creep resistance: Crastin® LW9020 ensures that vibrations made by the electric motor mounted on the frame do not generate harmonics in the part. At the same time, it allows the frame to absorb tensile, compressive and bending stresses resulting from the sliding roof’s operation.
Abrasion resistance: Crastin®’s very good resistance to abrasion withstands stress caused by the driving cable of the moving roof with minimal wear, while keeping good acoustic damping of the sliding roof.
Heat resistance: Being on a car roof, the part is exposed to high temperatures and sunshine, but the Crastin®’s high resistance to heat distortion, heat aging and UV radiation ensures that it keeps its dimensional stability.
Materials Selected and Why
DuPont™ Crastin® LW9020 was selected for its dimensional stability, non-warping properties, abrasion resistance, high resistance to heat distortion, UV radiation, excellent price/performance ratio, high stiffness, strength and creep resistance, acoustic damping, resistance to moisture and cleaning materials.
Designing and processing strengthening ribs into the part was easy, thanks to the good flow properties leading to short cycle times. The material’s good mechanical properties also ensure that the usual assembly processes do not damage the long, thin-walled front portion.
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