Efficient Identification of stability lobe diagrams

• Applicant: Professor Dr.-Ing. Christian Brecher
• Subject Area: Production Automation and Assembly Technology ; Production Systems, Operations Management, Quality Management and Factory Planning
• Term: from 2016 to 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 312052494

The obtainable productivity of modern machine tools is significantly limited by the occurrence of chatter vibrations. Chatter vibrations are self-excited and self-reinforcing regenerative vibrations, resulting from the interactions between process and machine tool. Despite of being the topic of numerous research projects, chattering is still not fully mastered and investigated. Therefore it is necessary to investigate the influences on stability extensively. However, the identification of stability lobes diagrams, which display the limits of stability and its dependency on cutting depth and rotational speed, is elaborate and poorly reproducible. There already exist two different approaches to reduce the experimental effort to identify the diagrams: the continuous variation of the cutting depth and the continuous variation of the rotational speed. However both approaches dispose some disadvantages regarding the experimental effort.The aim of the requested project is to develop a methodology to make the identification of the stability lobes diagrams more efficient, automatable and reproducible. The long term aim is to standardize the determination of stability lobes diagrams. The methodology is based on a combination of the two approaches mentioned above. The novelty is that not only one parameter, but the cutting depth as well as the rotational speed are variated. In this way, the stability limits are determined continuously. In a future second phase of the project it is planned to use the new methodology to investigate possibilities to compensate statistical influences on the identification of stability lobes diagrams.To develop the new methodology first the two existing approaches are further investigated to clarify the boundary conditions. Furthermore a method for the identification of chatter is chosen and advanced. Afterwards the new methodology is realized by combining the two approaches together with the identification-method and validated by experiments on machine tools. Afterwards the results are evaluated.The result of the project is a new experimental methodology to identify stability lobes diagrams efficiently and automated, which enables a simple and extensive investigation of influences on the stability of machine tools. In addition to that the methodology simplifies the identification of optimal process parameters for stable machining.

• DFG Programme: Research Grants
• Co-Investigators: Dr.-Ing. Alexander Epple; Dr.-Ing. Marcel Fey