Transcript 下載/瀏覽Download

Journal of Materials Processing Technology 140 (2003) 303–307
Investigation of micro-EDM material removal characteristics
using single RC-pulse discharges
使用RC單脈衝放電於微細放電加工之材料移除特性研究
Y.S. Wong a,∗, M. Rahmana, H.S. Lima, H. Hanb, N. Ravib
a Mechanical Engineering Department, 10 Kent Ridge Crescent, National University of Singapore,
Singapore 119260, Singapore b Singapore Institute of Manufacturing Technology, 71 Nanyang Drive,
Singapore 638075, Singapore
Class：碩研機械一甲
Student ID：MA310112
Student：陳肇文
Professor：戴子堯 教授
Date：2015/5/25
outline
• Abstract
• Introduction
• Experimental
• Results and discussion
• Conclusions
Abstract
• In micro-EDM, intense heat is generated between the work
piece and tool electrode by the discharge through a dielectric
medium to result in the formation of a micro crater that is
much smaller in size.
• It is found that at lower-energy (<50 μJ) discharges, the
energy required to remove the unit volume of material,
defined as the specific energy, is found to be much less than
that at higher-energy discharges.
• indicating greater consistency in shape and size when the
discharge occurs at lower energy.
Introduction
• The power supply of discharge energy and the resolution of
the X-, Y- and Z-axes movement.
• At low energies (10–20 mJ), the net metal removal efficiency
has been found to be near 1.0 and at higher energies (50–700
mJ), the efficiency is found to fall of rapidly until 0.15.
• The work presented in this paper aims to study the
mechanism of material removal by investigating the formation
of micro crater and its characteristics using very low single RCpulse discharge which is approximately 1000 times lower than
those in EDM, to shed a new light on this subject.
Experimental
Fig. 1. Micro craters at 2μm spark gap.
Fig. 2. Single-discharge RC circuit of micro-EDM.
Results and discussion
• A micro crater resembling that of a quarter moon shaped
structure in cross-section is produced using the single RCpulse generator.
• Fig. 1(a)–(f) show some examples of micro craters produced
using the single discharge on the sample.
• The critical problem in the single-discharge machining is the
unevenness in the size of the micro craters produced.
• Hence, five micro craters are produced at each machining
condition to determine the expected size.
Effects on the volume of micro crater
Fig. 3. Discharge energy vs. cavity volume of micro crater.
Fig 4. Discharge energy vs. average ratio of standard deviation (S.D.) to
Micro crater size.
Fig 5. Discharge energy vs. specific energy.
Conclusions
• The volume and size of the micro craters are found to be more
consistent at lower-energy discharges than at higher-energy
discharges.
• The specific energy required to remove the material is found to be
significantly less at lower energies (<50 .J) when compared with that
at higher energies.
• Using a simple theoretical model, the estimated erosion efficiency of
material removal at low-energy discharges is found to be seven to
eight times higher than that at higher-energy discharges.
• The aforementioned strongly indicate that lower-energy discharges
produce more consistent size of micro crater at higher efficiency.
Thank you for your attention！