Andreas Loderer

Experimental Verification of a Benchmark Forming Simulation

Forming of near-net-shaped and load-adapted functional components, as it is developed in the TransregionalCollaborative Research Centre on Sheet-Bulk Metal Forming SFB/TR73, causes different problems, which lead to non-optimal manufacturing results. For these high complex processes the prediction of forming effects can only be realized by simulations. A stamping process of pressing eight punches into a circular blank is chosen for the considered investigations. This reference process is designed to reflect the main aspects, which strongly affect the final outcome of forming processes. These are the orthotropic material behaviour, the optimal design of the initial blank and the influences of different contact and friction laws. The aim of this work is to verify the results of finite element computations for the proposed forming process by experiments. Evaluation methods are presented to detect the influence of the anisotropy and also to quantify the optimal blank design, which is determined by inverse form finding. The manufacturing accuracy of the die plate and the corresponding roughness data of the milled surface are analysed, whereas metrological investigations are required. This is accomplished by the help of advanced measurement techniques like a multi-sensor fringe projection system and a white light interferometer. Regarding the geometry of the punches, micromilling of the die plate is also a real challenge, especially due to the hardness of the high-speed steel ASP 2023 (approx. 63 HRC). The surface roughness of the workpiece before and after the forming process is evaluated to gain auxiliary data for enhancing the friction modelling and to characterise the contact behaviour.

Automated extraction and assessment of functional features of areal measured microstructures using a segmentation-based evaluation method

In addition to currently available surface parameters, according to ISO 4287:2010 and ISO 25178-2:2012—which are defined particularly for stochastic surfaces—a universal evaluation procedure is provided for geometrical, well-defined, microstructured surfaces. Since several million of features (like diameters, depths, etc) are present on microstructured surfaces, segmentation techniques are used for the automation of the feature-based dimensional evaluation. By applying an additional extended 3D evaluation after the segmentation and classification procedure, the accuracy of the evaluation is improved compared to the direct evaluation of segments, and additional functional parameters can be derived. Advantages of the extended segmentation-based evaluation method include not only the ability to evaluate the manufacturing process statistically (e.g. by capability indices, according to ISO 21747:2007 and ISO 3534-2:2013) and to derive statistical reliable values for the correction of microstructuring processes but also the direct re-use of the evaluated parameter (including its statistical distribution) in simulations for the calculation of probabilities with respect to the functionality of the microstructured surface. The practical suitability of this method is demonstrated using examples of microstructures for the improvement of sliding and ink transfers for printing machines.

Measuring Systems for Sheet-Bulk Metal Forming

In order to fulfil today’s demands on fast, efficient and sustainable production processes the sheet-bulk metal forming is being developed as a new forming technology within the scope of the SFB/Transregio 73. Characteristically for the sheet bulk metal forming is a three dimensional material flow, which allows for extensive freedom in the design process. To ensure maintaining all the advantages, provided by sheet-bulk metal forming, new inspection concepts for the produced parts as well as for the forming tools have to be developed. For a production-related inspection of produced parts a multi-sensor fringe projection system is under development, which will be employed to detect deviations of features’ form and size. With its sensors of varying measuring range and resolution a feature adapted inspection is possible. Additionally an optical fibre sensor is projected to detect small parts of interest in a very high resolution to enhance the possibilities of the multiscale multi-sensor system. A newly developed endoscopic fringe projection system is used to inspect parts that are out of reach for common optical measuring systems such as the forming tool of the process. This allows for a continuous measurement of tool features and thus the detection of slow growing wear. Challenging for measurement tasks in the sheet-bulk metal forming process are not only the complex geometries but also the harsh environmental conditions and especially for the parts’ inspection, the different surface parameters. In this article the surface parameters of the some sheet-bulk metal formed parts and forming tools will be explained, followed by a description of the different measuring systems. Finally an exemplary evaluation of the influence of the surface properties on an optical measuring system will be shown.

Ganzheitliche dimensionelle Messung von blechmassivumgeformten Bauteilen

Zusammenfassung Im Zuge der Erforschung und Weiterentwicklung des Fertigungsverfahrens Blechmassivumformung wird ein geeignetes Messverfahren zur Qualitätsbeurteilung benötigt. Dieses soll aufgrund der Prozessanforderungen eine ganzheitliche fertigungsnahe Prüfung der Bauteile ermöglichen. Dementsprechend ist ein Messsystem erforderlich, das auch in unmittelbarer Prozessnähe zuverlässig Ergebnisse von allen relevanten Bauteilmerkmalen liefert, welche sich signifikant in ihrer Größe und Form unterscheiden. Durch den mehrskaligen Multisensor-Ansatz, der die Kombination mehrerer Sensoren unterschiedlicher Messverfahren, -auflösungen und -bereichen erlaubt, konnte ein Messsystem für die Anforderungen der neuen Fertigungstechnologie entwickelt werden. Ein eigens angepasstes methodisches Vorgehen erlaubte eine strukturierte Messsystementwicklung mit verschiedenen Entwicklungszielen als Zwischenergebnis. Das resultierende prototypische mehrskalige Multisensor-Messsystem, basierend auf drei verschiedenen Streifenprojektionssensoren erlaubt dimensionelle Messungen von Merkmalen, deren Größe den Messbereich eines Sensors überschreitet. Hierdurch werden ganzheitliche Messungen von Bauteilen der neuen Fertigungstechnologie ermöglicht.

QUALIFYING MEASURING SYSTEMS BY USING SIX SIGMA

The technology of sheet-bulk metal forming enables the production of complex workpieces with filigree surface structures in only a few forming steps. In order to provide a rapid and production-related workpiece inspection of not only large workpiece features, but also small features in an appropriate quality, a multi-sensor optical measurement system with different resolutions is required. Workpiece features of medium size can be measured by two types of fringe projection sensors. With a structured approach according to Six Sigma, which is based on the five phases design, measure, analyze, improve and control complex tasks are divided into smaller individual problems. In each phase the Six Sigma method recommends tools for solving the individual problems effectively. With the support of the Six Sigma guideline an exemplary sheet-bulk metal forming workpiece feature is used in order to qualify the two measuring systems for a production-related measurement. After defining the explicit goal for the investigations, a detailed analysis of the measurement process leads to a couple of relevant influences. These are input factors for the design of experiments. By a full factorial design, not only an influence of a factor itself, also the interactions between multiple factors can be detected. In the analyze-phase, these results are calculated by different statistical methods. To present the results in a comprehensible way several types of diagrams are used. The shown approach gives an example for a traceable and methodical way to qualify a measurement system for challenging measurement tasks.