Achieving high standards of interior trim and general ambience has taken on an increasing significance for all car manufacturers, but for high-volume models it is always necessary to achieve quality together with appearance (including design variety), durability, and, particularly, thoroughly efficient and cost-effective processing.
To help OEMs achieve these requirements, Johnson Controls Inc. has introduced a high-frequency (HF) welding system that enables designs and 3-D imprints to be applied to trim covers of different quality via a simplified process but with the ability to achieve aesthetic personalization.
Interior design is likely to generate a sense of customer loyalty to a particular brand (Audi, Jaguar, and Mercedes-Benz are particular examples) because it creates a “family” identity across model pricing strata.
Marc van Soolingen, Senior Design Manager at Johnson Controls’ Automotive Experience at Burscheid, Germany, explained that seat covers are a significant part of this: “Whether it is sporty, robust, or elegant fabrics, decorative applications or the type of seams do give an interior a distinctive look, and special seat covers have an underestimated effect on the consumer’s perception of added value and their identification with the brand.”
To help achieve these identities within necessary cost:benefit ratios, Johnson Controls focused on simplifying the process and learned how to apply HF welding techniques to do so and to achieve required quality.
A complication with car seat design and build is that it usually comprises at least a dozen pieces—and often up to four times that number. Typically, though, distinguishing designs are just applied to the central panels of a seating surface and on backrests. These are achieved by weaving patterns into the material panels via a flatbed or “round-knit” process. They are then filled with a foam layer and facing material is applied.
This process is complex because different colored yarns and qualities must be used. “HF welding is a relatively simple application process, with complete seat appearance impact,” said van Soolingen. “Covers can be created in a uni-color fabric because all design elements are applied at a later stage. The desired designs in each case serve as the template for molds made from brass or aluminum produced via a 3-D CAD process."
Ready-to-cut pieces of the seating panels and a thin plastic foil are placed between the mold and an equally electro-conductive carrier plate. The HF welding process is then applied and an HF electromagnetic alternating field develops between mold and carrier plate.
“The dipoles of both materials are heated and consequently welded together,” van Soolingen explained. “The part is then taken out of the mold and any non-welded remnants of plastic foil discarded.”
OEMs may specify designs of numerous colors and materials. To meet such requirements, separate molds are constructed for each of those steps. Although this may sound complex, Johnson Controls’ Foam and Trim Product Business Manager, Peter-Gerd Müller, says that it is still faster and more efficient than having to include the colors and designs in the weave of the fabric and then apply further design elements of 3-D structures at a later stage.
He described the company’s HF welding technique of individual cover panels as being of such a high precision process that when different panels are sewn together they provide a perfect fit.
Following what is termed as a “rigorous” testing program, Johnson Controls is now manufacturing car seat covers using the HF welding process. It is also used for door panel applications.