Study On Evaluation System And Increasing Technology Of Reliability And Green In CNC Machining Center

Currently the level of domestic products is lower than that of the similar products overseas and cannot compete with them.Therefore, it is important to improve the reliability of machining center for increasing the national prestige, enhancing competitive ability in the international market as well as raising national manufacturing techniques.Along with unceasing expansion of the machining center, it initiates more and more serious environment questions. People request higher hopes about the machining center. They want the redundant reliability, saving energy as well as environmental protection. So it is really important to improve the reliability and green work in CNC machine. Besides, it is also inevitable to make it develop toward the direction of high-speed, high efficiency , high precision, high reliability and green.This work combined with national high-tech research and development plan (Plan 863) project "the strut research of appraisal for the reliability of CNC machine and the numerically controlled system". We took some domestically produced machining center as study objects and analyzed collected failure data for reliability and green analysis.We proposed the corresponding growth strategy according to the analysisThe reliable model analysis is the basis for the evaluation of reliability. Basing on different mechanisms in the different failure time of the machining center, we analyzed the failure data gained from machining center with mixed model for the first time. Single Weibull distribution model and double mixed Weibull distribution model contrast analysis were used for the failure data. We also used hypothesis testing for the goodness of fit examination separately. AIC criterion law was also performed for the model optimization selection. All the results proved that double mixed Weibull distribution analysis was better than single Weibull distribution model analysis. Based on evaluation and tendency test for the reliability with mixed Weibull distribution analysis, we peformed the growth tendency test for the reliability.For the first time, the extension fuzzy analytic hierarchy process was used to evaluate green degree of the machining center from user's angle. The green degree evaluation system and hierarchical level relations were established. Evaluation matrix of identical level index weight was made through the expert marking method. Evaluation indicators weight and extent of the membership were calculated for each level. Fuzzy comprehensive evaluation method was used to evaluate the indicators and the green degree of single indicator and the whole machine was obtained to provide the basis for improvement of green design, manufacturing as well as the management.We proposed to use one comprehensive method to analyze the failure in machining center for the first time. This method combined the primary and secondary chart of failure, the failure proportion with the failure mode effect and criticality.To find weak points of reliability and green in the machining center directly, the green failure mode effect was proposed for the first time.Based on the traditional failure analysis. We can find out the weak points of energy conservation and protection to determine the main attack direction of failure correction and provide basis for the improvement of design and management in the reliability .the failure proportion was also used in the failure analysis, we fully considered various requests in subsystems of reliability in the machining center based on the traditional FMECA. We also accurately reflected the difference between reliability and its indicators. Fuzzy comprehensive evaluation method was used to analyze the failure mode effect and criticality. Thus we can quantitatively process the uncertain failure information. According to the reasons of failure, we performed the reliability analysis and the potential growth analysis of green of Machining Center. Based on the traditional reliability analysis, we developed the design laws toward the green for the reliability of the machining center .According to the reasons of failure and the weak points, reliability of the machining center toward the green can be improved in design with some proposed measures .From the manufacturing of the key technology and assembly, some measures can also be proposed to improve the reliability. The way of Green procurement and supply chain was applied to assure the quality of Association of outsourcingBy comparing, the green and reliability of the new machining center and the old machining center are as follows:1) Improved reliability of the machining center indicators have improved to varying degrees, including time between failures from the 425.58 hours increased to 545.5 hours; average repair time and the failure rate have greatly reduced, the inherent availability has increased significantly.2) Comprehensive evaluation scores of the green of improved machining center increased from 56.35 points to 68.63 points, the green greatly enhanced. Machine has entered Green Machine ranks. From the view of failure mode,there are excessive noise.Failure mode such as excessive oil leakage and temperature greatly reduced, the majority of failures are random failures caused by improper operation of users.