Contact Area Evaluation of Digitalized Spotting Images as a Criterion for Die Tryout

Abstract

Increasing demands on the quality of outer car body panels and shortened product development processes of car models fundamentally challenge automotive manufacturers concerning international competition. In this respect, the tryout process carried out during the manufacturing of dies requires special consideration. Die tryout is generally characterized by time-consuming manual grinding operations aimed at producing homogeneous contact areas of the die surface zones. Here, blue color paste visualizes the contact areas of the dies and provides a spotting image. Afterward, the toolmaker uses his experience to qualitatively evaluate the different spotting images on both sides of the die and the blank in order to rework the tool surfaces appropriately. In this context, this paper presents a new approach for evaluating spotting images by using optical measurement technology and image processing. The method leads to a measurable quantitative size during the tryout of dies and standardized evaluation. For this, the active contact areas of die components are measured first in order to compare the current die performance with the forming simulation subsequently. Thus, a specific tryout state can be numerically defined, leading to a shorter and more efficient tryout by reducing manual grinding processes. During the investigations presented in this paper, spotting images of series dies were analyzed by implementing an image processing tool. Furthermore, a threshold value specification for the blue color of the measured spotting images was defined in order to distinguish between active and non-active contact areas.