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Surface generation mechanism in electrical discharge matching with silicone powder mixed fluid
The surface generated by electrical discharge machining (EDM) appears to be generally mat finish. However the machined surface in EDM with silicon powder mixed fluid becomes glossier and has a smaller surface roughness than that in conventional EDM with kerosene type fluid which leads to the omission of hand finish lapping of metai molds. The quality of machined surface significantly depends on the kind of workpiece material. But the surface generation mechanism has not yet been made sufficiently clear. In this study the effect of silicon powder mixing on the surface generation mechanism is experimentally investigated, analyzing the shape of crater generated by single pulse discharge, the surface roughness, the machined surface and so on. The main conclusions obtained are as follows:
1. The gap distance in EDM with silicon powder mixed fluid is
larger than that with kerosene type fluid, because of the lower resistivity of the former and the influence of silicon powder arrangement in the gap. EDM with silicon powder mixed fluid leads to smaller undulation of a crater, because the smaller impact force acting on the workpiece due to evaporation and expansion of
machining fluid. 3. The more the precipitated carbides in the workpiece are, the
larger the surface roughness is, since the carbides come off because of crack propagation due to the frequent heat impact
during EDM. 4. EDM with silicon powder mixed fluid results in the stable
machining without short circuit between the electrode and the
workpiece. उक्त जानकारी के आधार पर यह स्पष्ट होता है कि केरोसीन तेल में तीव्र इलेक्ट्रीक स्पार्क (discharge) पैदा होने पर भी आग नहीं लगती, क्योंकि केरोसीन के भीतर ऑक्सीजन उपलब्ध नहीं होता। यही स्पार्क यदि करोसीन की सतह पर होता तो भंयकर आग पैदा कर सकता था। इससे यह सिद्ध होता है कि स्पार्क स्वयं अग्नि नहीं है। at UFT HR-AE, 2004
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