Optimal positioning and design of multi-mass dampers within a combined topology optimization process

 

The continuous development of machine tools - WZM - with regard to increasing productivity and machining quality is achieved not least by penetrating the development process with computer-aided tools, especially when it comes to assessing the complex dynamic behavior. The Finite Element Method - FEM - has become an integral part of development, further development and problem analysis in the company.

The optimization of machine designs for dynamically highly stressed applications is now supported by automatic FEM-based structural optimization methods in addition to manual variant design and purely engineering considerations. In the early development stage, topology optimization is well suited to achieving optimal rough designs of structural components. An application for existing machine concepts, however, is sometimes uneconomical, as there is too little scope for structural changes.

In order to improve the dynamic behavior of existing machines as cost-efficiently as possible, dynamic auxiliary systems are well suited. Here critical resonances of the machine can be damped purposefully with passive, adaptive or active means and the dynamic behavior can be strongly influenced. In contrast to automatic structure optimization methods, however, dynamic auxiliary systems are regarded more as problem solvers in operation than as design elements to be used specifically in development.

The aim of the research project is to combine both above mentioned solution strategies in a holistic approach. In the first funding period, a novel, robust, passive damper system consisting of a large number of individual masses - a so-called multi-mass damper, or MMD for short - was researched and practically validated. This could contribute to a paradigm shift of the additional system as problem solver, if it is possible to embed the automatic positioning and design of this MMD in a holistic development and optimization process, which is suitable for industrial use in machine tool construction in the early development phase.

The main argument for the coupling of both approaches lies in the expected synergy effects resulting from lightweight structures (less damper mass required) with inner free spaces and distributed damper systems (less installation space required). A possible feasibility of such structures is strongly favoured in particular by the rapid development of additive manufacturing processes and opens up previously unrealisable optimisation potential.

One of the greatest challenges for the second phase of the research project lies in coupling the optimal design of MMD with a computationally efficient structural optimization process without the mutual influence of both optimization approaches jeopardizing the convergence of the overall process. In order to address this core problem, fundamental research into various coupling approaches already outlined in the first funding period in conjunction with different structural optimization approaches is essential. With the aid of additive manufacturing processes, the final practical verification will demonstrate the actually realizable synergy effects and serve as a starting point for a transfer of knowledge into practice, also beyond the machine tool industry.