The loss of all or part of the specified functions of the CNC machine tool is called the failure of the CNC machine tool.

The failure rate of CNC machine tools has obvious changes with the use of time, and its shape is shown in Figure 7.1. Because the shape of a typical failure curve is similar to that of a bathtub, it is called a bathtub curve or a machine tool failure rate curve, which is divided into three stages.

The first stage is the initial operating area, the curve is negative exponential, and the machine tool failure rate is high: the u stage is the effective life area of ​​the system. Generally, CNC machine tools can only enter the effective life area after 9-14 months of operation, so general CNC machine tools The warranty period is about 1 year. The machine tool entering the effective life zone has a very low failure rate; the IQ stage is the aging area of ​​the CNC machine tool. During this period, the system’s failure rate increases sharply with time. This curve helps us understand and analyze the occurrence of CNC machine tool failures.

CNC machine tool is a product of mechanical and electrical integration, advanced technology and complex structure. The failures of CNC machine tools are also diverse, and the causes of failures are generally more complicated, which brings many difficulties to the diagnosis and maintenance of CNC machine tools.

In order to facilitate fault analysis and diagnosis of machine tools, this section roughly divides the faults of CNC machine tools into several categories according to the nature of the fault, the cause of the fault and the location of the fault.