| With the continuous development and perfection of China’s technologies in machinery industry, great progress have been made in current domestic heavy-duty CNC machine tools in intelligence and precision.However, foreign imported brands have been dominating the heavy-duty CNC machine tool market due to the poor reliability level of domestic heavy-duty CNC machine tools. Current domestic research focuses on the reliability at the design phase rather than the reliability assembly process. Consequently,domestic high-end CNC machine tool manufacturers purchase foreign high-quality parts. Although these components themselvesare highlyreliable, the reliability of the product is still no match of that of foreignbrands after assembling. So it means that on no account should the utmost significance of the assurance technology of the assembly process reliability be undervalued.This paper researches on the protection methods of reliability assembly process of heavy-duty CNC machine tools based on the National Science and Technology major projects. On the basis of data analysis of the machine assembly process from the factory line,this paper draws up two methods to find out the key weak processes from the assembly process. One method is based on Bayesian group judgments theory combined with the FMECA while the other on the analysis of the assembly process by the model of directed graph theory. Then the quality control points are established, by improving and monitoring the quality control points.That is the key weak process of the assembly process to be controlled so as to realize inherent reliability of the machine during the protection.The main content of this research paper is as follows:(1)Research on the objects of the assembly process from the domestic heavy-duty CNC machine tools by analyzing the machine structure, the assembly process and the point of view From the corporate economic and practical. This article gets the conclusion: In the assembly process, defaults insome key weak processes account for most defaults in the total assembling process. By keeping the key weak assembly processes running well, we can guarantee good reliability of the entire assembly process. And this article makes the protect plan : Looking for the key weak processes of the assembly process and establish the quality control points, by improving and monitoring the quality control points, to achieve inherent reliability of the machine during the protection.(2) First drawing up a method to find the key weak processes from the assembly process based on Bayesian group judgments theory combine with the FMECA. And use the assembly process by the ram of the domestic heavy-duty CNC machine tools.Verified this method is effectiveness and correctness. Obtained the conclusion: the effectiveness of the group judgments is better than the single judgment.(3)Propose another method to find out the key weak processes of the assembly process based on the analysis of the assembly process by the model of directed graph theory, and then compared with the Bayesian group judgments theory. Verified the effectiveness and correctness of the two methods and emphasis the advantages and disadvantages of the each methods, at last obtained the use scope of the two methods.(4) After the key weak step has been selected, establish the quality control points, Propose how to establish the plan of quality control points. By using reliability theoretical knowledge, Drawing up the idea of some related documents such as < Assembly reliability checklist>. regarding this quality control points, making some improvement measures and monitoring the quality control points, which is the key weak process of the assembly process, the process can be protected. Finally, using hot charging and dynamic balance two assembly process as example.Narrating the step of establishing the control points. By enterprises the method in the factory, It verified the effectiveness of the protection method of the reliability assembly process of the heavy-duty CNC machine tools... |
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