Functional edge shaping of micro bores by applying electrochemical machining

Micro bores are used for several high-precision applications, especially in hydraulic systems and fuel injectors. In this case the shape, particularly the edge rounding of the injection spray hole, has a significant influence on the atomization of fluids and therefore also on the combustion process [1]. Usually these micro bores are machined by electrical discharge machining (EDM) [2]. In EDM sharp edges occur due to the process characteristics and a specific influence on the edge shape is not possible. Thus, a specific and independent adjustment of the edge rounding is required. To produce such a defined edge rounding of bores, an Electrochemical Machining (ECM) process has been investigated. This process is based on a localized anodic dissolution of the sample material that is connected to a positive electric potential. The advantages of this process lie in the possible high localization of the erosion process and high achievable surface quality. The tool which is the cathode has a negative potential and determined by the design of the edge rounding [3]. An experimental set-up was developed in order to perform the investigations. This paper presents the setup and experimental investigations.