High-precision optical coordinate metrology for punching tools by using a digital twin for the measurement strategy

The requirements in optical dimensional coordinate metrology are often not only to fulfill the measurement task but also to define the measurement strategy. One application of relevance is the automatic quality assurance of punching and stamping tools, which is often directly integrated into the manufacturing process. The measurement of surface finishes and micro-geometries with tolerances down to the sub-mu m range has a decisive influence on the quality, reliability, and durability of such high-precision components. The challenge of the measuring task consists of measuring complex micro geometries on free-form surfaces on the top as well as the vertical reference surfaces on the side. Existing tactile methods often do not allow high-resolution measurements of such free-form surfaces or require long measuring times. Existing optical measurement systems typically have a limited performance with respect to measurable slope angles. For an automatic measurement process, measurement planning as e.g., the number of measurements, their positions and probing directions are essential for high-accurate and repeatable measurements. The proposed measurement solution based on an optical micro-coordinate measurement machine (mu CMM) using advanced focus variation offers advantages in terms of the complete application including the measurement strategy. Focus variation and vertical focus probing enables the measurement of the free-form top-surface and the measurement of the vertical surfaces by optical lateral probing. The mu CMM metrology software provides algorithms that support the user in technology-based optimal measurement planning on CAD data by e.g., suggestions in terms of measurement method, probing direction or offline collision detection using a digital twin of the mu CMM.