Micro-pin Forming under Consideration of Vibrational Frequency

Abstract

Micro-forming tool is very important for micro-hole drilling. Electrical discharge machining (EDM) is used in micro-fabrication because of low reaction force. Moreover, micro-electrode is an important micro-tool. In this study, this paper proposes a micro-pin-forming method in which a rotating cylindrical electrode approaches a forming plate. As the processing area in this method is larger than those other methods, a higher removal rate is achieved compared to other methods. Moreover, a high aspect ratio of the micro-pin is achieved. A rotating WC-Co rod of 0.5 mm diameter is moved through the plate that is a zinc alloy plate of 2 mm width and 5 mm thickness. The result showed thad a micro-pin electrode of 90 μm diameter and 5 mm length can be gotten reproducibly. However, a micro-pin forming smaller than 10 μm in diameter is difficult to obtain using the machine tools currently available in the market. Miniaturization limits through micro-pin forming by the EDM are determined based on the discharge conditions, grain size of pin material, thermal residual stress, and lateral vibration of the micro-pin caused by the rotation of the micro-pin. In this study, it is considered that micro-pin vibration caused by its rotation, which affects the miniaturization limits. The rotational speed of the micro-pin is an important factor for high aspect ratio of the micro-pin forming. Finally, the forming of a micro-pin of 8 μm diameter and 250 μm length is performed considering the rotation of the micro-pin.