The fault curve can conceptually represent the relationship between the failure rate of CNC machine tool processing and time. Because this curve is shaped, it is often called "bathtub curve". It divides the service life of CNC machine tools into three stages, namely the early failure period, accident failure period and loss failure period. In the early stages of faults, the machine tool fault rate was negative index curve function.

At the beginning, the failure rate was very high, but as the operating time increased, the failure rate decreased rapidly, and the failure rate entered the constant phase. There are many reasons for early failure rates, such as design defects, manufacturing and installation errors, and hardware parts processing operations and use errors. After finding the cause of the fault and eliminating it, the failure rate will gradually stabilize. This stage is called the debugging period or running -in period.

The early failure period not only occurred in the initial stage of the new machine tools, but also occurred in the repair or replacement of parts processed by CNC lathes and re -entered it.

The occasional failure period is also called the effective failure period, the failure efficiency is very low, and the loss efficiency is constant. Under normal circumstances, this stage should not lead to major failures. It is a good working period with a good process of processing hardware parts. However, due to improper use, misunderstanding, or other accidents, some failures may also be caused. In addition, if the design stability coefficient of some components is small, the upper limit of the load will be encountered during use, which may cause damage and failure due to overload. Therefore, pay special attention to reasonable use, strengthen maintenance, avoid operational errors, and extend the effective life of the machine tool as much as possible during the accident failure stage.

After entering the efficiency of grinding loss, the fault rate increased again due to the normal wear, chemical corrosion, physical electrical performance changes, and material fatigue of the machine tool parts. For CNC machine tools, if various diagnostic technologies can be adopted, the loss of parts can be mastered, and corresponding maintenance or replacement measures can be taken before the parts enter the fault loss, the loss of loss can be controlled, thereby extending the actual actual CNC machine tools life.