Experimental study to prevent the surface crack during microgrinding of glassy carbon

초록

Glassy carbon (GC) is widely used as a mold material in the glass molding process (GMP) for fabricating glass-based optical components and biochips due to its excellent properties; however, it is difficult to machine because of its high hardness and brittleness. This study investigated process parameters, tool design for enhanced chip evacuation, and the critical depth of cut (CDC) to achieve high-quality, crack-free surfaces during GC microgrinding. A polycrystalline diamond (PCD) tool with a center groove, fabricated via wire electro-discharge grinding (WEDG), was used to improve chip removal. The CDC was found to be approximately 11.2 mu m; beyond this value, cracks occurred, and it further decreased as tool wear progressed. By using a depth of cut smaller than the CDC, a crack-free surface with a surface roughness (Sa) as low as 0.009 mu m was achieved. Layer-by-layer machining below the CDC effectively suppressed cracks and enabled gradual removal of pre-existing cracks. Additionally, lower feed rates and higher spindle speeds improved surface quality. This study provides a comprehensive process strategy for achieving precise, damage-free microstructuring of GC, contributing to advancements in high-quality precision mold fabrication.

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