Project area B

B02: Calculation and modelling of heat transfer mechanisms between machine components

The focus of subproject B02 is the numerical and experimental quantification of heat transfer between machine components. Heat transfer acts as a thermal boundary condition, thereby influencing the thermal behavior of machine tools. The first and second funding period aimed at the development of models for predicting heat transfer at static as well as moving machine interfaces and time dependent contact pressure. Furthermore, the impact of interstitial fluid on the heat transfer was investigated.

For the scope of the third funding period, methods derived from generic test cases will be enhanced for the investigation of applied scenarios, focusing on three dimensional geometries with limited optical access and moving thermal boundary conditions as they for example occur in bearings. Furthermore, the effect of cooling lubricant on machine tools is investigated using multi-phase CFD methods. With these methods, time and spatially resolved heat transfer coefficients at the tool, chip and workpiece can be quantified.

B03: Investigation of components and assembly groups

Subproject B03 focusses the impact of components and assembly groups on the thermo-elastic behavior of a machine tool. In this context, two key objectives are being pursued. One the one hand, metrological investigations on in-house developed and operated test rigs allow analyzing and evaluating the respective thermo-elastic behavior. Here, especially the friction characteristics of active components are explored deeply. On the other hand, the previously identified behavior is simulated with FE-models.

Furthermore, as integration object a motorized spindle is used to merge results from different subprojects in just one test object. Besides a metrological investigation, the development of an online-capable thermo-mechanical simulation environment is driven forward. By integrating control-internal data, a process parallel calculation of the spindle’s thermo-mechanical operation point is enabled.

In the 3rd phase, components and assembly groups are analyzed in the context of a machine tool.

B04: Identification of exemplary scattering and time-varying thermal model parameters

B04 develops methods and tools for an efficient parameter adjustment support. One focus is the planning of the adjustment during the commissioning phase. Therefore, uncertainty analyses for the determination of parameters to be adjusted as well as the design of load regimes for parameter stimulation, which are compressed in time and parallelized for the axis assemblies of the machines, are performed. The second focus is the adjustment of time-varying parameters in the operating phase. For this purpose, measurement values, measurement locations and measurement times are analysed and methods of stimulation detection and model error evaluation are investigated for suitability. Subsequently, methods for economic measurement will be developed primarily based on control data.

B06: Property model based correction of load dependent machine tool deformations

B06 develops a correction approach based on a grey-box model determining the misalignment of the tool center point (TCP) due to thermo-elastic mechanisms. During the 3rd phase all findings concerning the thermo-elastic overall error at the TCP and their behavior over the axes lengthes shall be used to derive a reduced application orientated measurement method. This method allows the measurement and correction during the chip removal with coolant. In addition, an approach to correct longterm drift of the model will be investigated.

B07: Structure model based correction of thermo-elastic errors at machine tools

B07 deals with the creation, commissioning and operation of the structure model based correction of thermal errors. In phase 3, the focus will be set on the deficits of the structure model based correction during runtime. This includes the determination of correction quality, susceptibility to faults and improvement potentials of the correction during commissioning as well as the monitoring and assurance of correction quality, robustness and availability during operation and at restart of the correction. The model calculations will be performed with fully automatic recourse orchestration on server clusters while ensuring high security standards.

B08: Model predictive parameter and state estimation and optimal sensor placement

The crucial challenge for the 3rd phase is the incorporation of uncertainties such as the thermal influence of fluid coolants and chips during the machining processes. These uncertainties can be characterized as highly varying in space and time and typically not normally distributed. Subproject B08 will address this added difficulty in predicting the TCP displacement using modern and efficient methods of uncertainty quantification, combined with novel regularization techniques.

B09: Identification of environment parameters of thermo-elastic models and correction algorithms based on high-dimensional characteristic diagrams

B09 develops a black-box thermal error correction method based on high-dimensional characteristic diagrams. The third phase focuses on the extension and improvement of the developed methods and tools for their application in complex production environments. This requires enhanced simulations with realistic transient load cases including radiation, micro-climates, coolants, chip nests and forced convection due to axis movements. Added complexity comes from the consideration of the entire machine tool including foundation and housing. A new decoupling method for fluid-dynamic simulations using characteristic diagrams will be improved and applied for more efficient machine tool thermal design optimization. The characteristic diagram based correction will likewise be adapted for realistic production environments. In order to cope with the added complexity, an alternative componentwise correction method will be developed and compared to the full model.

B10: Controller data based feed forward temperature field control of a machine tool (thermal pre-control)

B10 develops controller-based methods for deriving influencing strategies with the aim of reducing the changing rate in the temperature field of machine tools. This includes the control of additional equipment, such as fluidic and cooling systems, heat accumulators or the influencing of electrical drives. In detail, thermal footprints and a thermal look-ahead are developed and extended to a thermal pre-control.