Experimental and FEM-based Analysis of the thermal loads in deep-hole drilling process using twist drills and MQL

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The main aim of this project is the development of a high-efficient finite-element-simulation, in order to predict the thermally induced workpiece deviations in deep-hole drilling of complex aluminium cast alloy components using twist drills and minimum quantity lubrication (MQL) as well as to develop appropriate compensation strategies and to minimize the experimental effort. Due to this central objective, two different focuses have been defined within this third and last stage of the priority program (PP) 1480. The first emphasis is the implementation of a high-precision and with regard to the computing time optimized 3d-simulation of the drilling process, in order to achieve realistic calculated thermally and mechanically induced workpiece deformations during and after the machining process. Further enhancements of the model should also be able to map the borehole straightness deviation which remains after cooling down of the workpiece. The second aim of the project is the development of three innovative compensation techniques, which are fundamentally different and offer diverse advantages and disadvantages so that a combination of the strategies seems to be reasonable, too. At first, the process adaptation of the feed / the feed velocity / should be analyzed, since a higher feed rate not only induces a lower thermal load into the workpiece, but also allows higher productivity. In terms of the coolant concept, the MQL should be used furthermore within the project. The compensation of the thermal load is carried out by cooled compressed air, which is a reasonable alternative to the cryogenic concept, because of its advantages regarding to the handling, operational safety etc. Cryogenic cooling is frequently used in machining of hard-to-cut materials. The third compensation strategy is based on the synchronous radial movement of the machine tool spindle during the axial feed of the tool. Due to this NC-path compensation, the drilling axis can be modified over the machining process and the drilling direction can be controlled. Apart from the fundamental investigation of these compensation techniques the developed solutions will be transferred to complex application oriented demonstration components. At the end of this third and last stage of this project within the PP 1480 a holistic methodology of the analysis, modelling, simulation, prediction, and compensation of the thermally induced workpiece deviations will be presented.