Reliability Assessment Of Motorized Spindle Based On Performance Degradation

As the core function component of CNC machine tools to realize precision cutting,the performance and reliability of the motorized spindle is the key to determine the overall performance of CNC machine tools.Due to the fact that motorized spindles are highly reliable and long-life products,it is difficult to collect a large amount of failure data.Therefore,it is one of the hot issues in current research to evaluate the reliability of the motorized spindle by combining its main performance degradation information.Taking the motorized spindle of a series of horizontal machining centers as the research object,this paper selects the appropriate test items according to the failure analysis of the electric spindle,and considers the lower limit of life of the electric spindle to complete accelerated test time design.Combined with the test plan,the electrical spindle reliability test was conducted on the test device,and the performance degradation data was collected and consolidated to realize the reliability modeling and evaluation of the electrical spindle.Firstly,according to the structure and working principle of the motorized spindle,the component division of the motorized spindle is carried out.Combined with the field fault data collected in the previous period to apply the method of Fault Modes,Effects and Criticality Analysis(FMECA).Considering the correlation of failures,the method of Decision Making Trial and Evaluation Laboratory(DEEMATEL)was used to determine the key components and key failure modes of the electric spindle system.According to the analysis results to determine the corresponding test items.Secondly,the reliability model of the electric spindle was established combined with the field fault data of the electric spindle and determine the lower limit of life estimate for the product based on the model,which is the truncation time of laboratory test.The experimental load was determined based on the machining process information,and the optimal design of the test time under accelerated stress was performed based on the modified Miner fatigue cumulative damage theory.Finally,a reliability test device and a reliability test system are built according to the selected test project,the performance degradation data in the test is collected according to the proposed censored time and data acquisition plan.Using the confidence limit method to determine the basic failure rate function of the electric spindle,and using the performance degradation of the electric spindle as a covariate to establish the reliability covariate regression model considering multiple performance degradations,realize the reliability assessment of the electric spindle.The method proposed in this paper overcomes the problem of lack of failure data in the traditional reliability assessment work,and provides a reference for reliability evaluation of accelerated test.