| As the basis of modern industrial equipment，development of CNC machine toolsdetermines the overall level of the manufacturing industry. Steadily forward as theworld economy, people consider the use of CNC machine tools performance while itssecurity, economy and reliability of the increasing number of requests. Compared toimported CNC machine tools, especially high-end CNC machine tools, domestic CNClevel of reliability is not the fundamental guarantee. For the rapid development ofdomestic machine tool, its competitiveness in the market is still low. CNC machinetool reliability level is constrained by the level of reliability of its key features. Themajor national science and technology projects established reliability researchtopic-the reliability of the design and test technique of Key features, to enhance thelevel of reliability of the CNC machine tool from the point of research key features.In recent years, as the key features of CNC machine tools, chain-type toolchanger s reliability level had got more and more attention. In this paper, for studyingthe domestic chain-type tool changer, the reliability test bench of chain-type toolchanger was built. Through Frequent Tool change laboratory test, the chain-type toolchanger fault data were collected in a short time. Then the failure modes wereanalyzed and the fault data reliability model of the chain-type tool changer wasestablished to provide an important basis for the use and improvement of the product.The main contents are as follows:(1) Test bench overall design: Through the working mode of the chain-type toolchanger and the analysis of test bench, the test bench mechanical system was designed,including the overall and local structure and the calculation and analysis of the keyparts to ensure the safe and reliable of the test bench. By the selection of the lowerposition machine and the mode of control and data collection, the general scheme ofthe test bench control system was determined.(2) Test bench control system design: First, the three-phase control and thesingle-phase control circuit were designed. The electrical components selection was completed. The servo controller s speed loop and position loop parameters wereadjusted. Then, according to the PLC input and output points and the functions, thestyle of PLC was selected and the PLC input and output circuit was designed. Finally,the operation flow of the control system of the lower position machine was analyzedthen the PLC program modules were planned to complete PLC programming.(3) Test bench control procedures design: The upper monitor control system isdivided into two control terminal of the touch screen and IPC. The touch screensoftware-the EB8000, is for the development of control procedures and the design ofits human-machine interface. Its main function is to control the tool change action andautomatically shut down after failure. The Visual Basic program and itshuman-machine interface were designed. Its main function is to collect and store themachine operation and fault data to the Access database of the date as keyword.Failure is determined according to the applied sensors, inverter and servo controllerfeedback.(4) Reliability test research: Through the reliability test, the fault data werecollected and the failure mode was analyzed. As high levels of product reliability andlong test cycle, the fault data is limited to the small sample processing for thereliability assessment. The two-parameter Weibull distribution was chosen as theprobability distribution model of the time between failures of the chain-type toolchanger and Bayesian method was used to model the time between failures of thechain-type tool changer and to estimate the parameters. The tested chain-type toolchanger s MTBF estimated value is1989h.Early test proved that the test bench mechanical system is safe and reliable, andthe control systems and procedures are able to run stability and complete the desiredgoals. Bayesian-based small sample evaluation method is suitable for the chain-typetool changer s reliability assessment of the laboratory test... |
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