There is a growing interest in the machining of micro-holes with high aspect-ratio in difficult-to-machine alloys for the aerospace industry. Processes based on electro discharge machining (EDM) and developed for the manufacture of both micro-electrode and micro-hole are actually used, but most of them involve micro-EDM machines. In this work, the influence of EDM parameters on material removal rate, electrode wear, machining time and micro-hole quality when machining Ti6Al4V is studied. Due to an inefficient removal of debris when increasing hole depth, a new strategy based on the use of helical-shaped electrodes has been proposed. The influence of helix angle and flute depth with respect to process performance has been addressed. Main results include 37% reduction in machining times (hole diameter 800 μm) when using electrode helix angle of 45° and flute-depth of 50 μm, and an additional 19% with flute-depth of 150 μm. Holes of 661 μm diameter and as much as 6.81 mm depth, which yields in aspect ratio of 10:1, have successfully been machined in Ti6Al4V.

Experimental study on micro EDM-drilling of Ti6Al4V using helical electrode

This article is about the implementation of an acquisition system for the measurement of micro-electro discharge machining process parameters and the statistical analysis of their influence on the process performance. The micro-electro discharge machining drilling of 316L stainless steel with copper tubular electrodes was studied and the exchanged power was taken into account as a comprehensive variable able to represent the effect of the peak current and voltage on the final result. The direct proportionality between the exchanged power and the nominal process parameters was verified. A linear and non-linear regression approach was used in order to obtain predictive equations for the most important aspects of micro-electro discharge machining process, such as the machining time and the electrode wear.

https://journals.sagepub.com/doi/pdf/10.1177/1687814016676425

Micro-electro discharge machining drilling of stainless steel with copper electrode: the influence of process parameters and electrode size

Over the years, sinking electrical discharge machining has become one of the most important production technologies to manufacture very accurate three-dimensional complex components on any electrically conductive material. This article reports a literature review on the diversity of conventional and non-conventional materials that are used or have potential to be used as EDM electrodes. In addition, additive manufacturing of EDM electrodes are also reviewed.

Materials used for sinking EDM electrodes: a review

The tip shape of a blind micro-hole produced using micro electrical discharge machining varies with respect to the process parameters used during machining. The usual tip shape is a blunt geometry within the common range of applications, however, under specific machining conditions and machining depths, the tip shape changes drastically to an inverted concaved shape. The origin of such tip deformation in micro electric discharge machining of blind micro-holes was investigated. It was observed that debris particles produced during machining accumulated at the tip, formed a hill and functioned as a tool electrode especially when using fine machining conditions. The phenomena is elaborated experimentally with the affecting parameters to describe the wear mechanism. Open gap voltage, pulse energy and tool rotation speed are examined as varying parameters during the experiments.

Debris and consequences in micro electric discharge machining of micro-holes

High Speed EDM and Laser Drilling of Aerospace Alloys

This paper describes micro-hole machining of a copper plate using the electro-discharge machining (EDM) process. Tungsten carbide was selected as the material for the electrode and compared with a copper-electrode. A precision centreless grinding process was employed to grind the electrode down to the desired diameter. A series of experiments were performed on a traditional EDM machine to investigate the effects of electrode material polarity setting and of a rotating electrode. Results have shown that electrode wear and hole enlargement are both smaller when positive polarity machining is selected; whereas electrode wear is larger and machining speed is higher when negative polarity machining is selected. High-quality micro-hole machining in copper can be achieved by the proposed method.

F.-T. Weng

Papers

Micro-hole Maching of Copper Using the Electro-discharge Machining Process with a Tungsten Carbide Electrode Compared with a Copper Electrode