# Experimental Study on Micro-Grinding of Ceramics for Micro-Structuring
## 1 Introduction  
Ceramic materials have attracted attention as possible substitutes for metals for structural parts used in several industrial fields and multiple advanced industries due to promising characteristics, such as low density and high strength, as well chemical resistance [1; 2; 3; 4; 5]. However, the advantageous mechanical properties of ceramics can be a disadvantage in fine-shape processing [6; 7]. Owing to the high hardness of ceramic materials, the tool wear increases during mechanical processing, which increases the cost of processing; because of the brittle nature of these materials, the machined surface is not smooth or breaks irregularly. These issues limit the application of ceramics, particularly in fields that use structures of tens to hundreds of microns. Various types of unconventional machining methods have been attempted to overcome the challenges of ceramic processing. Laser machining involves melting and removing the material at the high temperature of the laser or modifying the surface of the material to reduce the cutting force and wear on the tool during machining. [PERSON] et al. used a picosecond laser to investigate the processing characteristics of aluminum oxide ceramics and proposed a model to predict the results of the machined surface using processing parameters, such as scanning speed and laser power [8]. In the grinding of oxidized zirconium ceramics using a diamond-coated tool, [PERSON] et al. achieved a reduction of the fracture toughness of the material and the machining force and changed the surface condition during processing with laser [9]. Electrical discharge machining (EDM) is a method involving material melted by high-temperature heat generated by a spark and removed together with a melting explosion. In the case of a non-conductive material, a conductive substance, such as copper, can be applied to the surface of the material to form an assisting electrode, and the surface material can be melted and processed. [PERSON] et al. studied the machinability of conductive ceramic composites based on alumina and zirconia using micro-EDM [10]. [PERSON] et al. applied a copper-based assisting electrode on the surface of zirconia ceramics to produce a conductive layer to proceed with EDM, and analyzed the material removal rate and the hardness of the high layer for retesting [11]. The use of machining methods that use a heat source, such as laser machining and EDM, can result in the formation of micro-cracks on the surface of the material because of the high temperature. In addition, heat can modify the material around the machining area and change its physical properties. Furthermore, EDM can cause a decrease in machining shape accuracy owing to the tool wear. Grinding with a diamond wheel can be considered when a uniform and smooth surface is needed in a material with high hardness. [PERSON] et al. studied the machining conditions to achieve the ductile-brittle transition in zirconia grinding using hybrid bond diamond tools [12]. [PERSON] et al. created a grinding simulation for silicon carbide machining and classified the damage that occurred on the surface [13]. The simulation results were compared with the experimental results obtained through actual grinding to machine a smooth ductile mode surface. However, such conventional grinding methods have several limitations, such as the long time required to improve the surface quality, the large size of the tool, and limitations regarding the shape of the material, because a large machining force acts when the tool and the material are in contact. The grinding method using a micro-scale tool has been applied to processing of high-hardness materials in various industrial fields such as micro-optics, micro-dies and -molds, and micro-scale medical devices [14; 15]. By adjusting the machining parameters, it is possible to achieve a crack-free surface in brittle materials using the ductile mode. Micro-tools can be relatively freely used to machine complex features of tens to hundreds of microns.