Electro-discharge ultra-fine drilling with carbon fiber electrodes

目前放电钻孔的加工极限是孔直径Dmin = 6.5微米和纵横比l/D = 7.5。通过小直径D的电火花加工钻孔的挑战包括工具电极的制造指导。在直径D <= 50微米的钻孔的情况下，不能使用常规的杆电极，结果是，所需的杆电极不能被使用。与传统电极相比，碳纤维作为工具电极在制造直径D在几微米是小直径D，良好的导电性K，以及低成本。然而，使用单根碳纤维作为工具电极用于电火花加工精密钻孔的研究还不够充分。本研究项目的目的是研究，开发，以及提供用于钻直径为10微米<= D <= 30微米且纵横比为l/D >= 10通过使用碳纤维工具电极的放电钻孔。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的技术研究。此外，还研究了工艺参数的基本关系，最大可实现的纵横比l/D，最小可实现的制造公差，最大可实现的去除率Vw，和再现性将是研究的主要焦点。研究项目完成后，有关材料的基础知识-相关的去除过程和工具与工件之间的相互作用以及使用碳纤维电极通过电火花钻削精确钻削单个孔的技术将是可用的。在本项目范围内开发的技术可用于制造膜、隔膜、空气轴承和微型进料器等组件，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.