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Micro features with high aspect ratios are one of the commonly encountered geometries found in micro products. In the literature, these structures are often used in demonstrator products machined by a micromilling process. In this paper, the challenges in micromilling thin ribs with high aspect ratios have been studied. Due to the scaling effect, micro-ribs have relatively low stiffness but high natural frequency. Therefore, on the one hand, average forces have to be controlled well to avoid structural bending or even damage, while on the other hand, micro features are unlikely to be excited by the dynamic forces. The characteristics of micromilling forces and their relationships to the machining parameters, namely, feed per tooth, depth of cut and width of cut, were studied theoretically by force models. In addition, the effects of different milling strategies (up-/down-milling) and tool paths on the quality of thin features have been investigated using FEM. The results allow measures to be taken to minimize the force effects and support the micro features during machining. The experimental results verify the theoretical studies. Thin ribs about 15 μm wide and with an aspect ratio of more than 50 were machined with good form and surface quality.

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Abstract. In recent decades micro-manufacturing becomes increasingly important. Complex multi-material and multi-functional products are required in industries such as bio-medicine, transport, consumer electronics etc. These products, however, cannot be made by single process. Combination of various shaping and assembling processes is required. This paper, gives a systematic overview on the topic of process changing. Clear and systematic process classification system and appropriate design and modelling strategy are presented. Special emphasis is put on planning of complex manufacturing chains. This paper shall help process engineers to make their decisions easier.