Concept of a correction mechanism to prevent the drift of a drill bit for micro deep hole drilling

摘要

Machining of micro parts is very demanding in terms of accuracy and precision of tools and machine components. Concepts for miniaturization of machine tools continuously drive various research fields of engineering. Some of these concepts cannot be realized by simply scaling down existing macro machine tools. In contrast, other concepts can only be realized by the small size itself. In that case the small size acts as an enabler for certain applications [1]. This is especially true in the production of micro deep hole bores, due to the high aspect ratio of hole depth to diameter. In this paper a machine concept for a micro machine to perform axial deep hole drilling in transparent polymethylmethacrylate (PMMA) round stock is presented. Target diameters of the round stock of < 400 μm and bore diameters down to 200 μm result in a very thin wall thickness of < 100 μm. Therefore the drilling course has to be coaxial to the round stock. Due to the high aspect ratio of up to fifty, initial tests have shown that the drill tends to drift in the material out of the round stock causing damage to the material and the chuck. For this reason, the central part of the machine concept consists of a correction mechanism that prevents the drift of the drill in the material. Because of scaling effects for small machine tools and small work pieces and due to the material properties the active correction mechanism is implemented on the side of the work piece. The concept of this correction mechanism will be explained and formulated in detail in this paper.