Assistive Electro Discharge Machining of AIN Ceramics

Abstract

Electro discharge machining process experiences limitation due to the non-conductive nature of the workpiece material. However, researchers proposed assistive EDM technique to machine nonconductive materials in the past. These assistive techniques require a minimal thickness of 100 µm conductive coating on the workpiece surface which usually takes longer time to coat the surface using PVD (physical vapor deposition) method. In this paper, a new modified assistive EDM method has been proposed to machine nonconductive Aluminum Nitride ceramics successfully. A three layers coating was used that included silver coating, carbon tape and silver nano-powder on a non-conductive aluminium nitride. This coating aids in conducting EDM operation due to the availability of conductive particles. Apart from the decomposition of dielectric that facilitates carbon particles on top of conductive carbon layer, coating itself also contributes in conductive silver particles. Therefore, carbon as well as silver debris that remains on the ceramics surface aids in continuous spark generation which in turn creates alternative thermal load and thus removes materials.

Understanding Material Removal Mechanism and Effects of Machining Parameters during EDM of Zirconia-Toughened Alumina Ceramic

“…The preparation time for the new coating was an hour and the experimental results suggest its effectiveness. The assistive electrode proposed in this study is different from those reported in literature and is prepared after initial investigative study with trial and error, as demonstrated in our previous studies and its thickness is 300 µm roughly [ 47 , 48 ].…”

Powder Mixed Micro Electro Discharge Machining of Aluminium Nitride Ceramic

“…First approach is to add secondary electrically conductive phase. However this kind of reinforcement affects mechanical properties of ceramics such as hardness, flexural strength and fracture toughness [5]. Second approach is to apply Assisting Electrode Method, where conductive coating is applied on top of insulating ceramics [6].…”

“…Second spark decomposes newly formed intrinsic conductive layer together with ceramics. Crucial aspect in maintaining s[ machining of non-conductive ceramics is formation of secondary intrinsic conductive layer and removal of this layer with ceramics [5][7] [8]. As long as this sequence is repeated steadily, machining of nonconductive ceramics is possible.…”