Thermal Interactions between the Process and Workpiece

According to an international status report, up to 70% of the errors in cutting production can be traced back to time- and process- dependant temperature fluctuations. In particular, thermal effects from processing lead to the deformation of machine components. This affects the tool and the workpiece. This paper considers the research into interactions between process-related and thermal deformations with a focus on the high-precision machining of large workpieces. Previously conducted investigations have demon- strated the effects of the heat flow into the structures of workpieces during the machining process. As one might expect, deforma- tion occurs, which leads to deviations in shape and position. In the same way, length changes due to process-heat transfer can be observed on the tool side. This leads to displacements of the centre point of the tool, which are dependent on the tool geometry and process parameters. However, resulting production errors can often be reduced by improved process control. Considering an exam- ple from the field of mould construction, this problem has been discussed from a practical perspective. Starting with experimental analyses, the heat flow into the workpiece related to the inherent deformation was measured. This was realised using thermographic systems and displacement sensors. Relevant parameters that have a significant influence on the process were to be identified in these tests. Heat-transfer effects were analysed while varying these parameters. In the same way, this should provide support for simulative analyses and facilitate the verification of these analyses. Using computer models, it was possible to detect and evaluate thermoelastic displacements before the processing. Based on this, the findings led to appropriate countermeasures, such as the use of a modified machining sequence. The aim of all of these investigations is the development of optimal machining strategies t o help reduce manufacturing errors.