Electro-discharge ultra-fine drilling with carbon fiber electrodes

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The current machining limits of electrical discharge drilling are a hole diameter of Dmin = 6.5 micrometer and an aspect ratio of l/D = 7.5 . Challenges of drilling by electrical discharge machining with small diameters D consist of the manufacturing guiding of the tool electrode. In the case of drill holes with diameters D <= 50 micrometer conventional rod-electrodes cannot be used with the result that the necessary rod-electrodes need to be prepared by electrical discharge dressing which in turn leads to a considerable increase of manufacturing costs.Compared to conventional electrodes the main advantages of carbon fibres as tool electrodes regarding the manufacturing of drill holes with diameters D in the range of a few micrometers are the small diameters D, the good electrical conductivity K, as well as the low costs. However, the use of single carbon fibres as tool electrodes for precision drilling by electrical discharge machining is not sufficiently investigated.Goal of this research project is the investigation, development, and the provision of manufacturing technologies as well as machining strategies for drilling of cylindrical holes with diameters of 10 micrometer <= D <= 30 micrometer and aspect ratios of l/D >= 10 by electrical discharge drilling with carbon fibre tool electrodes. Since no knowledge about the material-related removal process exists a technological research in dependence to generator parameters and dielectrics is necessary. In addition, the investigation of the fundamental relationships of process parameters, the maximum achievable aspect ratio l/D, the minimum achievable manufacturing tolerance, the maximum achievable removal rate Vw, and the reproducibility will be in the main focus of the research.After completion of the research project fundamental knowledge about the material-related removal process and interactions between tool and workpiece as well as technologies for the precision drilling of single holes by electrical discharge drilling with carbon fibre electrodes will be available. The technology that is to be developed in the scope of this project can be used for manufacturing of components like membranes, spinnerets, air bearings, and micro-feeders and can help to reduce manufacturing time and costs.