Assembly Accuracy Reliability Evaluation And Its Process Design Method Of Heavy Duty Machine Tool

As a key part of nuclear pressure vessel, water chamber head long-term work at high temperature, high pressure and corrosive conditions. Its design, material selection and manufacturing etc have very strict requirements. Such parts weigh dozens of tons to hundreds of tons. Its workpiece material is generally low-carbon alloy steel. While such material’s hardness is not high. But it has higher toughness, higher strength and poor cutting performance. Because of heavy cutting force, high cutting temperature, intense vibration, complex cutting load changes, madding extreme demands on the carrying capacity and vibration resistance of the machine. Therefore, developing a high level of heavy-duty CNC machine tool’s design and manufacturing technology and CNC gantry mobile milling machining center for water chamber head, to meet the needs of large-size, large-tonnage, high-accuracy nuclear power parts’ accuracy machining and batch production, have important practical significance to promote nuclear power equipment manufacturing technology and the development of domestic heavy-duty CNC technology.As the structure of machine tool is hugeness, after initial assembly inspection, some parts need to be disassembled and transported to the production site for secondary assembly, demanding high assembly precision reliability of machine tool. This machine tool has big assembly deformation and cumulative error, so adopting repairs grinds, cut and try frequently in assembly. This method leads to full stroke coordinating low precision among bed, column, guide and beam etc, poor assembly precision and reliability, can not meet the need of machine tool moving parts smooth and steady, reliable delivery precision and power. This paper aims to above problems exist in water chamber head CNC gantry mobile milling machining center, studies on heavy duty machine tool assembly accuracy reliability and design methods of assembly process, the main contents include:To meet the special water chamber head turning, milling, boring functional requirements, research function and structure, assembly process of machine tool, establish evaluation of machine tool’s assembly accuracy reliability, reveal mapping relation between and structure, build assembly process hierarchy of machine tool, by analyzing assembly load and variate, proposing process design scheme of machine tool’s assembly accuracy reliabilityAdopting multi-body system model to analyze the formation of the initial error of the machine assembly, reveal influence factor and accumulation of initial error, propose solving method of machine tool components geometric error sources, contacting error sources and the whole assembly initial error, evaluate initial assembly process of machine tool and detect error.Aiming at characteristic of machine tool’s assembly accuracy changing with assembly processes, representing the process of initial assembly precision migration, repeat assembly precision migration and assembly precision migration when machine tool running, researching mapping relationship between machine tool’s assembly accuracy and deformation field, proposing identification method of deformation field influence factor of machine tool and key process variables, establishing assembly precision migration criterion of machine tool, constructing assembly precision migration model of machine tool, revealing the formation, growth and change mechanism of assembly precision migration, proposing design assembly process method of machine tool and doing example verification.Aiming at assembly precision design requirements of water chamber milling machining center, analyzing deformation characteristics of ram which is B-axis’ important component, establishing solver model of the front face of ram component, by judging structural design scheme of machine tool B-axis, getting structural design scheme which is corrected of B-axis component to meet design requirements and verifying the effect of program.