Precision machining is a process in which processing machinery is used to change the shape or performance of a workpiece. According to the temperature state of the workpiece to be processed, it is divided into cold processing and hot processing. Generally processing at room temperature, and does not cause chemical or phase changes of the workpiece, it is called cold processing. Generally, processing at higher or lower than normal temperature will cause the chemical or phase change of the workpiece, which is called thermal processing.