Study of engineering ceramic machining with a new design of ripple controlled microdetonation of electrode arc striking

Abstract

Based on the principle of strong shock wave generating transient dynamic high-pressure, physical theory of vacuum discharge, and high-power pulse technology, this study developed a new machining system of ripple controlled microdetonation of electrode arc striking (MDEAS), which was specially used to machine hard and crisp materials, such as ceramic. The topographies such as hole, ladder plane, column surface, and abnomity plane is machined successfully with the system on Si3N4 ceramic. Test results show that there is one deteriorative layer with thickness of 0.25 ∼ 0.45 mm on the test piece surface after MDEAS machining. The deteriorative layer is composed of amorphous phases and crystalloid Si, can be machined and removed with ceramic tools or common grinding wheel. There are obvious transverse cracks near the interface of the degenerative layer and the matrix, but the cracks along the depth direction are not found. Furthermore, the optimal machining parameters for Si3N4 ceramic are obtained through orthogonal experimental. The analysis on the machining mechanism proves that one negative pressure zone will form in the spherical space below the concave due to the action of negative peak overpressure when the detonation pressure attenuates to the negative peak overpressure, which has closure effect for the original microcracks on the material surface and subsurface, so the residual stress will not be produced on the deep layer inside the work piece material to cause the reduction of material strength. Compared with other machining technologies, because Si3N4 ceramic is disposed by the compositive way of detonation and gasification machined with the MDEAS technology, the technology has many outstanding merits such as low machining cost, well parameter controllability, and machining stability. So, it has an important applied value.