The main precision secondary processes of advanced ceramics

Precision technical ceramics have different secondary processing methods according to different performance requirements. At present, the main processing methods include mechanical processing, electrical processing, ultrasonic processing, laser processing and composite processing. Hereby we mainly introduce the mechanical processing technology of advanced ceramic materials, including turning, grinding, drilling, lapping and polishing.

1) Precision turning

Turning mainly uses high hardness and super wear-resistance diamond tools to cut ceramic materials. Polycrystalline diamond tools are difficult to produce smooth cutting edges, and are generally only used for rough machining; Natural single crystal diamond tools are used for fine turning of ceramic materials, and micro-cutting is conducted in the processing. Due to the high hardness and brittleness of ceramic materials, it is difficult to ensure the accuracy of turning processing, so turning processing has been not widely used, and it is basically still in the R&D stage.

2) Precision grinding

Grinding has been widely used in the machining processing at present. The grinding wheel is regularly diamond grinding wheel. Different scholars have different explanations for the grinding mechanism of diamond grinding wheels, but in general, the common point that is brittle fracture is the main reason for the formation of material removal. In the grinding process, the removal of chips is a major problem, and cooling fluid is generally used for cleaning. The coolant not only plays the role of flushing the chip powder, but also can reduce the temperature of the grinding area, improve the grinding quality, and reduce the thermal decomposition of the binder around the abrasive particles. Grinding fluids are generally selected with good cleaning performance and low viscosity. Diamond grinding wheels have different grinding characteristics due to different types of binders and abrasive particle concentrations. The size of diamond particles is another main factor that affects the surface quality of ceramic workpieces. The larger the particles, the greater the surface roughness, but the higher the processing efficiency.

3) Precision drilling

Drilling of ceramic materials is mostly used with trepanning drill. The structure of the trepanning drill is that an annular diamond grinding wheel is welded to a hollow steel pipe, and the welding process is silver welding. When drilling ceramic materials, the diamond grinding wheel rotates at high speed and uses the diamond abrasive grains on the end face to cut the material.

4) Lapping and polishing

In some areas of industrial production, grinding alone cannot meet the surface finish requirements of ceramic parts, that`s why lapping and polishing are usually conducted after machining. On the other hand, ceramic materials are less ductile and brittle, and their strength is easily affected by surface cracks. If the machined surface is rougher and the surface cracks are larger, it is easier to produce stress concentration, resulting in lower strength of the workpiece. Therefore, lapping is not only to achieve a designated roughness and high dimensional & shape accuracy, but also to improve the strength of the workpiece. Polishing is a finishing process that uses a soft polisher and fine-grained abrasives to act on the workpiece at low pressure.