The SKZ Plastics Center, in cooperation with the Institute of Psychology at the University of Würzburg, has completed the OFHarmonie research project on the relationship between the surface structure of plastic components and color perception. This issue is of considerable importance for industries that use plastics in applications with high aesthetic requirements, in particular the automotive sector, where adjacent components with different surface textures are expected to appear visually consistent. The key challenge is that structural differences can impair the subjective color matching of components installed next to each other, even when their nominal color values are similar.
Within the project, researchers analyzed up to which level differences in surface structure are acceptable to observers and which compensation approaches can reduce the negative impact of these differences on color perception. The long-term objective is to develop a method that can predict how colors must be adjusted to achieve the highest possible continuity of color perception for different surface structures and thus user acceptance. Developing such guidelines is relevant both for design and for quality control in the production of plastic components.
Scope and methodology of the study
The research work was based on a broad analysis of test specimens in which both surface structure and coloration were systematically varied. Classical measurement techniques were used to record color, brightness and gloss parameters, as well as parameters describing surface properties. These were supplemented by advanced industrial image processing methods, which enable a more detailed visual characterization of the tested components.
An important element of the project was psychometric studies aimed at systematically capturing the subjective assessments of observers. The data obtained were then compared with the results of instrumental measurements. This combination of objective measurements and subjective ratings made it possible to determine limits of acceptable differences and to better understand the mechanisms of color perception depending on surface structure. The conclusions from these analyses form the basis for developing practical recommendations for industry.
Project results and further work
The results obtained in the OFHarmonie project show that color measurements carried out in isolation from other parameters are not sufficient to explain the differences caused by varying surface structures. To achieve a more complete description, it is necessary to consider brightness, gloss and surface parameters together. The researchers emphasize that only such an approach enables a more reliable link between measurement data and the actual visual impression of components as perceived by users.
The image processing methods used in the project proved to be a promising tool for describing and differentiating surface structures in the context of color harmony. In the future, these techniques may complement classical quality control procedures, especially where a high level of visual matching is required for parts produced from different plastics or with different manufacturing technologies. The results suggest the possibility of further development of predictive models that will take into account more than one type of measurement data.
Timo Grunemann, head of the spectroscopy group at SKZ, points out the significance of the project for industrial practice: "The findings from OFHarmonie are an important step for the industry. They show that we cannot control visual harmony solely on the basis of pure color values, but must actively take surface structure into account. This opens up new possibilities for design and quality assurance." According to Grunemann, the project has established important foundations that can now be used for further research work.
Relevance for industrial applications
The conclusions from the OFHarmonie project provide important impetus for industrial color and surface design. The developed approach can support companies in optimizing the visual harmony of plastic components, especially in applications with high sensitivity to appearance, such as vehicle interiors. By combining color measurement results with surface structure parameters, it is possible to achieve better matching of components installed next to each other, even if they differ in texture.
Knowledge of the thresholds of differences that are acceptable to users can also be used when defining production tolerances and drawing up material specifications. The research findings are relevant for plastics producers, processors and end users who place emphasis on repeatability and visual consistency of products. Potential applications also include segments such as consumer electronics and other products in which plastic components with different surface structures must form an aesthetically uniform whole.
Project 01IF22811N, carried out by the research association Fördergemeinschaft für das Süddeutsche Kunststoff-Zentrum e.V. (FSKZ), was funded by the German Federal Ministry for Economic Affairs and Energy through the project management agency Deutsches Zentrum für Luft- und Raumfahrt e. V. (DLR) under the program for the promotion of industrial collective research IGF, based on a resolution of the German Bundestag.
How does the surface structure of plastic components influence the visual perception of color? SKZ and the Institute of Psychology at the University of Würzburg investigated this question in the OFHarmonie research project. (Photo: Luca Hoffmannbeck)
