Accelerated Life Testing For ATC System Of CNC Machining Center Based On Load Spectrum

Accompany with the development of modern manufacturing industry,machine center has been widely applied into the manufacturing industry for its unique function—automatically tool changing and multistep processing.Meanwhile,the reliability is becoming an important factor of machine center which determines its production efficiency.As a key functional component of machine center,ATC system(which is short for Automatic Tool Changing system)has a pretty high failure rate.So it's very necessary for researchers to study the reliability of ATC system.At present,for the lacking of load spectrum,the reliability test of the ATC system,which simulates the real working condition well,couldn't been done precisely in the laboratory,let along the ALT(which is short for accelerated life testing).To solve this problem,this paper proposed an accelerated life testing method for ATC system of machining center based on load spectrum.The mainly work of this paper are as follows:1)In order to build the load spectrum of ATC system,a field data acquisition specification has been drawn up.According to the specification,researchers has obtained the field data of ATC system.Then by processing the data,the reliability model and index,as well as the tool changing times of every tool and tool magazine has been obtained,which lays the foundation for the load spectrum and accelerated life testing.2)Through distribution model preselecting,parameters solving and model optimization,the load spectrum of single tool quality and total quality of all tools installed in the tool magazine have been built.Besides,the two-dimension load spectrum of single tool quality and total quality of all tools has been built with Copula function.3)The ALT plan for ATC system,which chooses the tool changing frequency asaccelerating stress,has been developed.In order to obtain the threshold value of accelerating stress and realize the customizing tool changing,a set of motor temperature collecting system has been established and the control system of the existing testing bench has been improved.According to the load spectrums,the loading program in the ALT has been developed.4)The data obtained in the test has been processed.Based on the MTBF in different stress conditions,an accelerating model for the ALT of ATC system has been built and the model has been verified by the MTBF in normal stress condition.Besides,the accelerating factor in different stress level has been calculated.