Fraunhofer-Institut für Produktionsanlagen und Konstruktionstechnik IPK

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Automatic design and synthesis of control for a plug and play active vibration control module

2018 , Uhlmann, E. , Kushwaha, S. , Mewis, J. , Richarz, S.

In this paper, a technique for automatic robust control design and synthesis for plug and play active vibration control module is presented. Robust control theory offers the uncertainty analysis and graphical manipulation of the frequency response as well as analytical solution approach. The prior knowledge of the plant model imposes limitations on the fast and effective implementation of the robust control. Moreover, the design of the weight functions for the robust control is usually a trial and error process. The plant identification and subsequent control design becomes even more tedious for modular devices with plug and play capability. In the present paper, the plant model is identified by using polyreference least square complex frequency estimator and an innovative automatic pole clustering algorithm. The HIF loop shaping robust control is designed, where the parameters of the weight functions are optimised using genetic algorithm. An experimental evaluation is also presented on a prototype modular structure.

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Twisted deep hole drilling tools for hard machining

2016 , Uhlmann, E. , Richarz, S.

The availability of high performance twisted deep hole drilling tools has been a significant innovation achieved some years ago. The use of these tools in machining centres permits substantially higher productivity and flexibility compared to existing deep hole drilling tools or alternative manufacturing processes for holes with a high aspect ratio. The aim of the present work is the systematic consideration of twisted deep hole drilling tools for reliable and economical hard cutting operations with a high level of quality assurance. In particular, a detailed analysis of manufacturing flaws and tolerances in tool making as well as their influences on the tools performance and the dynamic process behaviour has been conducted. It is shown that twisted deep hole drilling tools can be successfully applied not only with a high productivity but also for a high quality production of hardened components. A prerequisite to this, however, are holistic and precisely controlled process steps including appropriate clamping devices and a suitable high pressure lubrication strategy as well as the availability of high performance tools manufactured with high precision and low tolerances. In this context the symmetry of the tool shown to be of vital importance for the tools performance and the quality of the drilled holes.

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Zerspanung von Titanmatrix-Verbundwerkstoffen

2012 , Uhlmann, E. , Roeder, M. , Richarz, S.

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Oberflächenvorbehandlung und Kantenpräparation an Hartmetallwerkzeugen

2009 , Uhlmann, E. , Richarz, S. , Mihotovic, V.

Durch die geeignete Auswahl der Bearbeitungsstrategien für die Oberflächenvorbehandlung und Kantenpräparation lassen sich die Standzeiten von beschichteten Zerspanwerkzeugen deutlich steigern. In diesem Beitrag werden die Ergebnisse experimenteller Untersuchungen vorgestellt, bei denen das Strömungsschleifen und das Laserstrahlabtragen als Vorbehandlungsverfahren für Hartmetallsubstrate vergleichend gegenübergestellt werden. Für die Untersuchungen wurden Proben aus Ultrafeinstkornhartmetall mit 7 % Kobaltanteil mit einer AlTiN- Modifikation im PVD-Arc-Verfahren beschichtet (Schichtdicke 3 Mikrometer). Durch das Strömungsschleifen von Hartmetallwerkzeugen konnte eine Verbesserung der Oberflächengüte, eine Reduktion der Kobalt-Binderphase und eine Erhöhung der Druckeigenspannungen erzielt werden. Dagegen konnte das Laserstrahlabtragen zu keiner deutlichen Steigerung der Oberflächengüte und der Druckeigenspannungen beitragen. In Untersuchungen zur Schichthaftung konnte nachgewiesen werden, dass die Vorbehandlung einen entscheidenden Einfluss auf die Verschleißmechanismen hat. Während Beschichtungen auf strömungsgeschliffenen Substraten vorwiegend adhäsiv versagen, kann die Schichthaftung durch Laserstrahlabtragen derart gesteigert werden, dass kohäsives Versagen auftritt. Zusammenfassend ist festzustellen, dass die Auswahl des Vorbehandlungsverfahrens weniger auf die Glättung der Oberfläche, sondern vielmehr auf den dominierenden Versagensmechanismus der Beschichtung ausgerichtet sein muss. Die Ergebnisse deuten darauf hin, dass das Laserstrahlabtragen die Haftung der Beschichtung im Vergleich zum Strömungsschleifen signifikant steigert.

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Substitution of Coolant by Using a Closed Internally Cooled Milling Tool

2017 , Uhlmann, E. , Riemer, H. , Schröter, D. , Sammler, F. , Richarz, S.

The saving of raw materials plays a major role in industry and is becoming increasingly important. In the field of cutting technology, the aim is to maximise practices such as the substitution of coolant and the steady increase of tool life in order to make an effective contribution towards environmental protection. Concerning the saving of coolant and to enhance the performance in dry machining a milling tool with a closed internally cooled system was developed. Heatpipes are applied which ensure improved heat dissipation from the cutting edge because of their excellent thermal conductivity. The dissipated heat is subsequently delivered to the surroundings via a heat sink. This contribution describes how the performance of a standard tool can be enhanced by the integration of a closed internally cooled system. Simulations of the heat distribution in the tool have been conducted to design and optimise the prototype. Hence, milling tests on duplex steel and temperature measurements in the cutting process have been carried out to verify and further optimise these simulation results.

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Machining of carbon fibre reinforced plastics

2014 , Uhlmann, E. , Sammler, F. , Richarz, S. , Heitmüller, F. , Bilz, M.

The implementation of carbon fiber reinforced plastics (CFRPs) in the aeronautical industry has increased dramatically in recent years due to their favourable combination of low weight and high strength as well as the adaptability of their material properties. In order to economically and reproducibly machine these materials with high part qualities, improvements in machining strategies must be made. The focus of this paper lies on innovative technologies for the machining of CFRPs whereby CVD diamond coated tools and milling tools for the improvement of milling processes have been designed. Furthermore, water jet cutting, CO2 jet cutting and grinding of CFRPs has been investigated. The quality of the machined workpieces is also an issue which requires addressing, particularly in relation to the fraying of machined edges. An innovative quantitative method for the evaluation of the workpiece quality of CFRP is presented.

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Vollhartmetall-Schaftfräser für die Hartbearbeitung über 65 HRC

2011 , Uhlmann, E. , Richarz, S. , Sattel, S.

Im Werkzeug- und Formenbau sowie in der Automobilindustrie liegen Bauteile aufgrund hoher Einsatzbelastungen oft im gehärteten Zustand vor. In Zusammenarbeit mit dem Institut für Werkzeugmaschinen und Fabrikbetrieb (IWF) der TU Berlin hat der Werkzeugspezialist Gühring praxisgerechte Werkzeuglösungen untersucht, um die etablierte Prozesskette zu verkürzen.

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Machining of Carbon and Glass Fibre Reinforced Composites

2016 , Uhlmann, E. , Sammler, F. , Richarz, S. , Reucher, G. , Hufschmied, R. , Frank, A. , Stawiszynski, B. , Protz, F.

The combination of carbon and glass fibres in new reinforced composite components makes the machining of these promising materials challenging. The abrasive carbon and glass fibres cause tool wear and cutting edge rounding which results in higher process forces and insufficient workpiece quality. At the IWF, innovative process strategies for the machining of these materials have been developed, combining these with new cutting tool geometries. Furthermore, the classification of workpiece quality for reinforced plastic components has not been sufficiently addressed thus far and is also a focus of the work being undertaken. In order to adequately describe the workpiece quality, fibre pull-out and fibre protrusion must both be analysed. Using the example of a carbon and glass fibre composite material, the dependency of these characteristic quality parameters on process and tool parameters shall be analysed. The work described here compares an axial drilling with an helical milling process from both a technological (workpiece quality) and an economical (processing time) point of view.

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Smarte Werkzeuge für harte Werkstoffe

2012 , Roeder, M. , Uhlmann, E. , Richarz, S. , Fürstmann, P.

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Hartdrehen von PM-Schnellarbeitsstahl

2011 , Uhlmann, E. , Richarz, S. , Fuentes, J.

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