Project area A

A01: Deformations of cutting tool and clamping devices and workpiece fixture devices and of the impact on cutting edge and workpiece deflections targeting on their optimization and compensation

Thermal caused tool and workpiece fixture device deflections

The process heat during cutting processes causes thermal tool deformations and therefore reducing machining accuracy. In the sub-project models for correction and compensation will be developed. Possibilities of selective influencing of the tool temperature by air flows aimed at constant or predictable tool temperature distribution, heat elimination in the tool, insulation of the tool and the use of auxetic structures in order to compensate thermal expansion are taken into consideration. The investigations include numerical simulations (FEM, CFD) and experiments using the specially developed test bench.

A02: Model and method for the determination and distribution of converted energies in milling processes

The milling process is one of the most significant heat sources in machine tools. The overall objective of Project A02 therefore is a parameterized model for heat and temperature distribution for metal cutting processes, especially the milling process. In the first phase a modular modelling method based on potential theory was developed. The model explicitly considers location, type and strength of boundary conditions and heat sources. The second phase focuses on the transfer of this fundamental model to real machining processes, i. e. integration of real cutting geometries and wear. The model will be validated against productivity, energy and quality on the integrator “spindle”.

A03: Modells and methods for measuring and balancing the energy distributed in grinding processes

The overall objective of the subproject A03 is the development of a parameterized process model to describe the energy flows during grinding. In the first research period, the energy conversion and thus the heat sources during grinding were identified. In the second period, the stationary heat propagation will be investigated. Based on the identified heat sources and the relevant heat transfer mechanisms, the temperature distribution for the components involved in the grinding process (workpiece, grinding wheel, chips, coolant) will be modeled. Thereby, the real grinding wheel topography with statistically shaped and distributed abrasive grains is considered for the first time.

A04: Thermo-energetic description of fluid power systems

Fluid power systems and components play a major role in the targeted control of the temperature distribution of milling machines. As drive tasks for feed motion, tool and part clamping are receding further and further into the background, tempering of the machine tool is becoming more important – especially under the focus of a small thermo-elastic deformation.
In the project’s first phase, basic principles and calculation methods have been developed. These, as well as the achieved experimental results show that significant potential for effective tempering and, thus, reducing thermo-elastic deformations lies in improving the heat transfer in components. Furthermore, compensation and correction strategies require novel fluid system structures allowing a local and process-adapted tempering of machine subsystems.
At the component level, the sub-project aims at optimal heat transfer conditions with adapted cooling duct structures and geometries. For this purpose, e. g. modifications of cooling sleeves in motor spindles, which represent a main heat source inside the machine, are comprehensively analyzed. The developed methodology can also be used to adjust the channel structures in valves, heat exchangers and machine frames as well as for the optimization of cooling pumps.
At system level potentials for effective tempering of different consumers arise from individual, process-adapted and demand-orientated power and cooling units by reducing the heat input and the machines’ thermo-elastic deformations. Especially within the cooling system the consumers such as electrical cabinet, spindle and rotary table have different demands for temperature control, which also depends on the current operating mode. Against this background, the sub-project analyses variations in structure and topology of cooling systems depending on the consumers’ individual requirements. Furthermore, operating strategies are developed and evaluated in terms of a demand-orientated feedforward and feedback control of the supply units.

A05: Simulation of active machine tool models

Project A05 works on the pose and process dependent thermoelastic simulation of machine tools. Two model characteristics are research fields: (1) models in FE environment and (2) models in block diagram environment. The modeling of inner relative movements between machine components is essentially in booth model characteristics.
In the first stage these “moving models” are realized successfully. In the next grant period the main research fields are the following: merging SFB/TR specific submodels and parametrization methods in full machine models with inner movements – this is an aim in booth model characteristics (1) and (2); and automatic block diagram generation over the – current executed manually – steps CAD – FE – MOR – block diagram.

A06: model order reduction

The simulation of the thermo-elastic behavior, as well as the correction of thermally driven deviations from the desired production accuracy of machine tools, in real time requires model reduction techniques. The main focus is to develop assembly group network models of entire machine tools (in cooperation with A05 and A07) and corresponding tailored model order reduction methods with respect to given accuracy demands. Therefor, new guaranteed error bounds need to be developed. In particular methods for parametric model order reduction for coupled systems need to be developed, and will be included into, e.g., parameter identification problems (in e.g., B04).

A07: High-accuracy thermo-elastic simulation on massively parallel computers

The aim of the SFB/TR 96 is to establish a tool development process considering different correction and compensation methods and valuates their cost efficiency. This evaluation uses reduced models (A06) for each component and complete models, where are components are coupled together. The coupled model will be used to validate the reduced models, which was successfully done in the first phase. In the second phase, we have to combine different tool components, leading to the following tasks:

  • Thermo-mechanical simulations of moving components
  • Development of efficient and stable coupling strategies, which are efficent on HPC-systems within our FEM software AMDiS
  • Development of parallel time integrators, which are capable to resolve long process cycles
  • Parallel simulation of fluid dynamics (A04) in complex geometries.

All tasks together enable us, to simulate the virtual demonstrators and validate the correspond-ing reduced coupled models from A06.