Experimental investigation of surface characteristics and dynamic effects at micro milling of hardened hot-work tool steel

One of the main trends in modern manufacturing technology is miniaturisation. In this field, micro milling offers the most flexible machining method. Size reduction results in special and unique characteristics with respect to the machining process. The current paper addresses the investigation of the dynamic effects and surface characteristics of micro milled structures. Experiments were carried out on AISI H13 hot-work tool steel with 50 HRC hardness using a five-axis micro milling centre: cutting force components and the vibration signal were recorded and analysed. By means of fast Fourier transform, the dominant frequencies of the process were identified. Time-frequency diagrams were prepared by short-time Fourier transform for studying process changes during cutting time. Also, correlations between surface roughness, burr formation and cutting parameters were investigated. The results of this research provide a deeper understanding of the micro milling process, which ensures well-controlled and reproducible machining of up-to-date materials.