The failure curve can conceptually represent the relationship between the failure rate and time of CNC machine tool processing. Because the shape of this curve is like a bathtub, it is often called "bathtub curve". It divides the use period of CNC machine tools into three stages, namely, early failure period, occasional failure period and wear failure period.
The failure rate of the machine tool in the early failure period exhibits a negative exponential curve function. At the beginning, the failure rate is very high, but as the operating time increases, the failure rate quickly decreases and enters the constant failure rate stage. There are many reasons for the high early failure rate, such as design defects, errors in manufacturing and installation, and errors in the processing and use of hardware parts. The cause of the fault was found out after running-in and eliminated, and the fault rate gradually stabilized. This stage is called the trial run period or running-in period.
The early failure period not only occurs when the new machine tool is put into use, but also when the parts processed by the CNC machine tool are repaired or replaced and put into use again.
The occasional failure period is also called the effective failure period. In this stage, the failure rate is the lowest and the failure rate is constant. Under normal circumstances, this stage should not cause the main fault. It is the best working period for hardware parts processing. However, due to improper use, operating errors or other unexpected reasons, some failures can also be caused. In addition, if some components are designed with a small safety factor and encounter the upper limit of the load in use, they may be damaged due to overload and malfunction. Therefore, special attention should be paid to reasonable use during the accidental failure stage, maintenance should be strengthened, operation errors should be avoided, and the effective life of the machine tool should be extended as much as possible.
After entering the period of wear and tear, due to the normal wear and tear of machine tool parts, chemical corrosion, changes in physical and electrical properties, and material fatigue and other aging processes, the failure rate has risen again. For CNC machine tools, if various diagnostic techniques can be used to master the wear and tear of parts and components, and corresponding maintenance or replacement measures can be taken before the parts enter their failure period, the occurrence of wear and tear can be controlled and the CNC machine tool processing of the equipment can be prolonged. The actual life span.