Model and method for recording and balancing the energies converted in milling processes

 

The Collaborative Research Center Transregio 96 "Thermo-energetic Design of Machine Tools" aims to optimize the design and operation of machine tools in terms of productivity, energy consumption and manufacturing quality in the context of thermal behavior. In subproject A02 of the Collaborative Research Center Transregio 96, the focus of the investigation is on the converted energies and temperature fields in the milling process. The aim of the project is the analysis of causal and statistical relationships between process parameters and thermal state variables, such as heat flows and temperature fields. These have a direct influence on tool wear in the process, dimensional accuracy and surface integrity. The first step of the work included fundamental empirical investigations in the form of orthogonal cuts to estimate the heat input into the tool, workpiece and chips as a function of the machining work performed and the process parameters cutting speed and chip thickness. In principle, these heat inputs were determined by temperature measurements with thermography and pyrometry and the application of the first thermodynamic principle under simplified assumptions. In the orthogonal sections, the validity of the PÉCLET number could be shown as a heuristic for estimating the heat flow distribution.

A further goal of the project was the analysis of the transient, volumetric temperature fields in the tool during the milling process and their modelling. The empirically modelled and regression approximated time-variant heat flow into the tool was coupled with an analytical temperature model based on GREEN'S functions. The predicted temperature fields were compared with the measured time-varying fields on the tool face.

In the follow-up project and the third and last phase of the Collaborative Research Centre, the effect of the cooling lubricant medium will be considered. Here, both empirical test series based on the methods and measuring principles already developed and analytical and numerical models for quantifying the effective cooling effect are planned.