Electro-discharge ultra-fine drilling with carbon fiber electrodes

目前电火花钻孔的加工极限为孔径Dmin = 6.5微米，长径比l/D = 7.5。小直径D电火花钻孔加工的难点在于工具电极的加工导向。在钻孔直径D <= 50微米的情况下，不能使用传统的杆电极，其结果是需要通过放电修整来制备必要的杆电极，这反过来又导致制造成本的大幅增加。与传统电极相比，碳纤维作为工具电极制造直径D在几微米范围内的钻孔的主要优点是直径D小，导电性K好，以及成本低。然而，利用单碳纤维作为工具电极进行精密电火花加工的研究还不够充分。本研究项目的目标是研究、开发和提供碳纤维工具电极电火花钻削直径为10微米<= D <= 30微米，长径比为l/D >= 10的圆柱孔的制造技术和加工策略。由于不存在与材料相关的去除过程的知识，因此有必要进行依赖于发电机参数和电介质的技术研究。此外，研究工艺参数的基本关系，最大可实现长宽比l/D，最小可实现制造公差，最大可实现去除率Vw和再现性将是研究的主要重点。在完成该研究项目后，将获得与材料相关的去除工艺和刀具与工件之间相互作用的基础知识，以及碳纤维电极放电钻孔单孔精密钻孔技术。在该项目范围内开发的技术可用于制造膜、喷丝板、空气轴承和微型给料器等部件，并有助于减少制造时间和成本。

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.