Abstract
Micro-hole fabrication at a high speed and accuracy of machining while maintaining high surface quality is challenging. A core difficulty is the removal of the products of machining from extremely narrow gaps. To solve this problem, this study proposes an approach that combines high-speed electrical discharge machining (EDM) with electrochemical machining (ECM) by using a helical tube electrode with matched internal and external flushing. During high-speed electrical discharge drilling, matching the internal flushing with the clockwise rotation of the helical electrode can help remove debris from the bottom of the blind hole. During ECM, matching the external flushing with the anticlockwise rotation of the helical electrode can improve the flow of electrolyte in the gap. First, the flow field was simulated to show that matching the internal and external flushing of the helical electrode can enhance the flow of the medium and reduce particle concentration in extremely narrow gaps. Second, a series of experiments were conducted to verify that the taper of the hole and the surface quality of its wall can be improved by using the helical tube electrode. Finally, an experiment was carried out to optimize the machining parameters and yielded a minimum taper of 0.008 at a speed of rotation of 460 rpm, and pressures of internal and external flushing of 9 MPa and 4 MPa, respectively.
Highlights
In the context of aviation manufacturing, a large number of microscopic cooling holes are present in films on the surfaces of the turbine blades of aero-engines [1,2,3], and these micro-holes are distributed on the blades at different angles [4,5,6]
To better remove machining products from narrow gaps, this study proposes matching internal and external flushing with the rotations of a helical tube electrode in a combination of high-speed electrical discharge machining (EDM) and electrochemical machining (ECM)
Micro-holes with few defects and small tapers can be produced by a combination of high-speed EDM and ECM using a helical tube electrode with matched internal and external flushing
Summary
In the context of aviation manufacturing, a large number of microscopic cooling holes are present in films on the surfaces of the turbine blades of aero-engines [1,2,3], and these micro-holes are distributed on the blades at different angles [4,5,6]. To better remove machining products from narrow gaps, this study proposes matching internal and external flushing with the rotations of a helical tube electrode in a combination of high-speed EDM and ECM. During ECM, matching the external flushing with the anticlockwise rotation of the helical electrode is conducive to electrolyte flow in the gap This method can help accelerate the renewal of the working fluid in a combination of high-speed EDM and ECM. Micro-holes with few defects and small tapers can be produced by a combination of high-speed EDM and ECM using a helical tube electrode with matched internal and external flushing. U, v and w are the components of the fluid particle velocity in x, y and z directions, P represents the stress tensor
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