Journal of Digital Convergence (디지털융복합연구)

The Society of Digital Policy and Management (한국디지털정책학회)
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Efficient Arc Detection and Control Method in Electro-discharge Machining

방전가공기의 효율적인 아크 검출과 제어방법

  • 박양재 (가천대학교 컴퓨터공학과)
  • Received : 2018.10.31
  • Accepted : 2018.12.20
  • Published : 2018.12.28
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Abstract

In this paper, propose an efficient arc detection and control method to achieve fast machining speed, improved precision and surface roughness in discharge machining, especially for carbide and hard material processing and metal processing using discharge phenomenon as energy. A single discharge waveform is divided into three sections of Td (Time-Delay), Ton (Time-on) and Toff (Time-off) and the gate control timing is simulated using the HDL language. In this paper, we analyze the effect of the gap between the electrode and the workpiece on the machining results by determining the operation of the servo mechanism by sampling the Td section through the comparator circuit. As a result of the analysis, the Td section of the formed waveform was more precisely sampled at a high speed and the results were improved when applied to the gap control between the electrode and the workpiece.

방전 현상을 에너지로 이용하여 금속을 가공하는, 특히 초경 및 난삭 소재의 가공과 정밀가공에 효과적인 방전가공 시 빠른 가공속도와 향상된 정밀도 및 면조도를 달성하기 위하여 효율적인 아크의 검출과 제어방법에 대해 연구하였다. 단일 방전 파형을 Td(Time-Delay), Ton(Time-on), Toff(Time-off)의 세 가지 구간으로 나누어 HDL 언어를 이용하여 게이트 제어 타이밍을 시뮬레이션 하고, 실제 방전가공기에 적용하여 파형을 실측하였으며, 비교기 회로를 통한 Td 구간의 샘플링을 통해 서보기구의 동작을 결정함으로써 전극과 가공물 간의 간격 제어와 가공 결과에 미치는 영향을 분석하였다. 분석결과 형성되는 파형의 Td 구간을 보다 정밀하게 고속으로 샘플링하여 이를 토대로 전극과 가공물 간의 gap 제어에 적용하였을 때 보다 향상된 결과를 나타내었다.

Keywords

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Fig. 1. Discharge circuit

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Fig. 2. Normal state of discharge wave

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Fig. 3. Abnormal state of discharge wave

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Fig. 4. Logic signal output by threshold voltage

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Fig. 5. FPGA state machine

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Fig. 6. Flow-chart of gap controlling between software and firmware

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Fig. 7. KOJIN EDM Discharge board ver 2.0

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Fig. 8. Captured wave of wide-Td setting

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Fig. 9. Captured wave of narrow-Td setting

Table 1. Ionization energy of several elements

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Table 2. Wide-Td Parameters

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Table 3. Narrow-Td Parameters

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