Research Of Modeling And Control Technology Of Assembly Fault Rate Of CNC Machine Tools

The researching of high-precision, high-speed, high reliability, high efficiency hasbecome the important direction of CNC machine tools. The reliability of CNC machinetools not only has effect on the working status, but also affects the product marketingshare and the developing of our country industry technology. Due to the characteristic ofCNC machine tools, the assembly fault accounted for most part of the entire life-cycleof CNC machine tools, and even if the domestic CNC machine tools manufacturers buyforeign high-quality components which have the higher reliability, the reliability ofproduct assembled by those components is still not reach the level of foreign. Therefore,the fault or reliability analysis and control technology in assembly process play animportant role in improving the reliability of product.Based on the support of National Major Scientific and Technological SpecialProject, make the domestic machining center for the study, the modeling and controltechnologies of CNC machine tools were researched. The main content is as followed:â‘ Researched on the basic theory ofassembly fault rate of CNC machine tools:started with the characteristic of CNC machine tools production, the classification of thefault rate based on product life cycle and the study characteristic of assembly fault rateof CNC machine tools were analyzed; the relationships between assembly fault rate andassembly reliability were discussed based the relations between fault rate and otherreliability index; the5M1E method was applied to the attributes analysis of assemblyfault rate of CNC machine tools based on the attributes analysis of Assembly ReliabilityEvaluation Method(AREM); at last the research structure of assembly fault rate of CNCmachine tools was established, hence those study provides the theoretical basis forfurther research of CNC machine tools assembly fault rate or assembly reliability.â‘¡R esearched on theextracting and modeling of attributes of CNC machine toolsassembly fault rate: first, the Delphi method was used to quantitatively research for thecomplete attributes of assembly fault rate, and triangular fuzzy numbers was applied tothe fuzzy optimization for the results; then the algorithm of rough sets combined withgrey relation analysis was applied to the extraction of main attributes of CNC machinetools assembly fault rate, the extracted main attributes not only provide the improvedobjects for further research, but also can verify the method of modeling and extractionby the prediction error analysis; and then least square support vector machines (LSSVM) was introduced to model the attributes of CNC machine tools assembly fault rate, andthe genetic algorithm was used for the optimization for the model; at last some domestichorizontal machining center was taken as an example to verify the effectiveness of themodel and analysis method.â‘¢R esearched on theverifying, analysis and control technology of the attributes ofCNC machine tools assembly fault rate: the BP neural network model of main attributeswas firstly established for verifying the modeling and extracting method, and theprediction errors of different inputs of different models were compared, the modelingand extracting method was proved by the data of the machining center. Then, theassembly fault improvement of CNC machine tools was focused on the verified mainattributes. To grantee the effectively improvement of assembly fault, the process ofdesign for six sigma (DFSS) was improved combined with the research characteristic ofassembly fault rate of CNC machine tools, the Failure Modes and Effects Analysis(FMEA) had provided the bases for the whole analysis process, and then the method ofdesign stage improving combined assembly process stage controlling was applied to theeffectively improving of assembly fault of CNC, at last, the controlling and improvingof the machining center were explained in detail for verifying the improved analysisprocess and technology.