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Mechanical micromachining is a very flexible and widely exploited process, but its knowledge should still be improved since several incompletely explained phenomena play a role on the microscale chip removal (e.g. "minimum chip thickness effect", microstructure influence on cutting forces, stable built-up edge, etc.). Several models have been developed to describe the machining process, but only some of them take into account a rounded-edge tool, which is a typical condition in micromachining. Among these models, the slip-line field model developed by Waldorf for the macroscale allows to separately evaluate shearing and ploughing force components in orthogonal cutting conditions, therefore it is suitable to predict cutting forces when a large ploughing action occurs, as in micromachining. The present study aims at demonstrating how this model is suitable also for micromachining conditions. In order to achieve this goal, a clear, modular and repeatable procedure has been developed for objectively validating its cutting and feed force prediction performance at low uncut chip thickness (less than 50 µm) and relatively higher cutting edge radius. The proposed procedure makes the model generally applicable after a suitable and 2 non-extensive calibration campaign. The present paper shows how calibration experiments can be selected among the available database of cutting trials basing on the model force prediction capability. Final validation experiments have been used to show how the model is robust to a cutting speed variation even if the cutting speed is not among the model quantities. A suitable set-up, especially designed for microturning conditions, has been used in this research to measure forces and chip thickness. Tests have been carried out on 6082-T6 Aluminum alloy with different cutting speeds and different ratios between uncut chip thickness and cutting edge radius.

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