Safe, Strong & Green for up! Seatbelt System
When you are developing a lightweight, environmentally-friendly vehicle like the Volkswagen up! subcompact, those characteristics have to be considered for every little part, all the way down to things like the ratchet wheel in its seatbelt retractor system. So Key Safety Systems (KSS; keysafetyinc.com) selected a low-emission polyoxymethylene, Hostaform S9364 XAP2 from Ticona (ticona.com) to produce the wheel, as well as the ejector in the belt buckle.
This is a 1979 Mercedes-Benz G-Class, the first year the model appeared with its Schwarzeneggerian robustness, which happens to be incased in a block of amber-colored resin: Unlike the insects that are sometimes found encased in actual amber, objects that you can hold in your hand, this object measures 5.50 meters long, 2.55 meters wide and 3.10 meters high.
There is a lot of discussion about how 3D printing/rapid prototyping/additive manufacturing is revolutionizing manufacturing, including automotive manufacturing.
A problem with plastics and steel structures is a difference in the coefficient of expansion. Some material modifications may ameliorate that problem.