The fault curve can conceptually represent the relationship between the failure rate and time of CNC machining. Because this curve is bathtub-shaped, it is often referred to as the "tub curve." It divides the service life of CNC machine tools into three stages, namely early failure period, accidental failure period and loss failure period. In the early stage of failure, the failure rate of the machine tool is a negative exponential curve function.
The failure rate was high at the beginning, but with the increase of operating time, the failure rate dropped rapidly and entered a stage of constant failure rate. There are many reasons for the high early failure rate, such as design defects, manufacturing and installation errors, hardware part machining operations and usage errors. After running and running to find out the cause of the failure and eliminate it, the failure rate will gradually stabilize. This stage is called the commissioning period or the run-in period.
Early expiration occurs not only in the initial stages of a new machine tool being put into service, but also when a CNC lathe machined part is repaired or replaced and put back into service.
Occasional failure period is also called effective failure period, the failure rate is very low, and the failure rate is constant. Under normal circumstances, this stage should not cause major failures, and it is a good working period for hardware parts processing. However, some malfunctions may also occur due to improper use, misoperation or other unexpected reasons. In addition, if some components are designed with a small stability factor, they will encounter an upper load limit in service, which may lead to damage and failure due to overloading. Therefore, special attention should be paid to rational use, strengthening maintenance, avoiding operational errors, and extending the effective life of the machine tool as much as possible in the stage of unexpected failure.
After entering the wear failure period, the failure rate rises again due to the normal wear and tear of machine tool parts, chemical corrosion, changes in physical and electrical properties, and material fatigue. For CNC machine tools, if various diagnostic techniques can be used to master the wear and tear of parts, and take corresponding maintenance or replacement measures before the parts enter the failure and wear period, the occurrence of wear and tear failures can be controlled, thereby prolonging the actual operation of CNC machine tools. life.
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