The triple-layered structure manufactured from thermoplastics is characteristic of the sandwich moulding process. The outer skin is formed using novel materials, which determine the surface structure of the part. Regranulates can be used as a core component to cut costs, while a material containing a blowing agent can be used to avoid sink marks and to reduce the clamping force. In both cases, identical material is used for the skin and core components. Other adaptations are the insertion of a barrier layer or the creation of a solid core in a soft or galvanised skin layer.