Machine Tool Dynamics - A constrained state-space substructuring approach

Doctoral thesis, 2016

Metal cutting is today one of the leading forming processes in the manufacturing industry. The metal cutting industry houses several actors providing machine tools and cutting tools with a fierce competition as a consequence. Extensive efforts are made to improve the performance of both machine tools and cutting tools. Performance improvements are not solely restricted to produce stronger and more durable machine tools and cutting tools. They also include knowledge about how the machine tools and cutting tools should be used to perform at an optimum of their combined capacity. Information about the dynamic properties of the machine tool cutting tool assembly is one of the aspects that carries the most potential in terms of productivity increase and process reliability. This work presents a methodology to synthesise the dynamic behaviour of a machine tool and cutting tool assembly based on component models of the machine tool and the cutting tool. The system is treated as an assembly of subcomponents in order to reduce measurement effort. The target is to get the receptance at the tip of the machine tool/cutting tool which is a prerequisite for process analysis and optimisation. This methodology is compared with today's state-of-the-art methodology which require experimental testing for each cutting tool of interests mounted in the machine tool. Comparisons are also made with previous attempts to utilize component synthesis in this matter. The subcomponent approach presented here limits the experimental tests to the machine tool component. The machine tool component model is connected to a model representation, based on a finite element model of the cutting tool. The subcomponent models are obtained and coupled on state-space form, a technique that is new to the application of component synthesis of machine tool/cutting tool structures. Proposed procedures for measurements, system identification, enforcement of physical properties on state-space models and parameter influences on coupled results are presented, implemented and validated. This methodology opens windows not only to cutting process optimisation of an existing cutting tool but it also permits tailored cutting tool solutions for existing machining operations with fixed process parameters.