“Cool” moldings are decorated with real metal

Experts from the labs of Germany’s IKV (Institute for Plastics Processing; Aachen, Germany) say they have simplified the process of decorating an injection molded part with real metal, a move they predict may find welcome takers in the automotive industry because, although a car’s interior is now almost 100% thermoplastic, true metal’s haptics remain in high demand.

Such multimaterial parts also could see use in exterior automotive parts as well as in other industries such as the white goods or consumer goods sectors.

Metallic-look parts formed by back injection molding against a metallic-look thermoformed film are not new, but these films do not give a consumer the cool feel of real metal. Molded parts have been decorated with metal but usually at a relatively high cost and requiring some sort of secondary processing. The IKV’s project also involved back injection molding, but onto a sheet of metal. The real novelty of the process is a coating on the metal that helps standard thermoplastics such as PC/ABS to adhere to the metal. Additional adherence can be created by forming, for instance, mechanical joints between the metal and the plastic. During the process, the pressure of the plasticated melt forces the metal sheet against a mold cavity’s wall, where it takes on the structure of the cavity.

The IKV has worked with another Aachen-based institute, the IBK (Institute for Production), to test its new back injection molding technique, and says initial results indicate that integrated parts using 0.2-mm-thick aluminum or stainless steel sheet are possible, with the quality and detail realized on the metal surface dependent on the thickness of the metal sheet. Ongoing tests are using metal sheet of other thicknesses, and efforts are being made to integrate injection molding simulation software with software used for simulating metal forming so that users can reliably predict results from the process. —Matt Defosse