Research On Assembly Accuracy Reliability Of Heavy Duty Machine Tool And Design Method Of Assembly Process

Geometry constraint and physical constraint change because the structure is complex, tonnage is large, and assembly load is complex on heavy duty machine tool, affected by the repeated assembly and long-time vibration, the structure parameters of combined will change surface under repeated disassembly or variable load, then, the assembly accuracy reproducibility and assembly accuracy retentivity decline, which results in the decrease of assembly reliability. But assembly accuracy reliability directly affects the assembly quality formed by assembly process, even affects the machining accuracy of workpiece.The subject comes from high-end CNC machine tools and basic manufacturing equipment major science and technology issue "the head of the water chamber dedicated mobile gantry CNC milling machining center (2011ZX04002-111)".The performance and assembly accuracy of machine tool was analyzed in this thesis, the structure, function and performance of machine tool was decomposed, the mapping relation between performance and assembly accuracy was established. Through the analysis of the connotation of reliability, the hierarchical structure of assembly accuracy was ensured, then, the hierarchical structure of performance of machine tool, target of assembly process design and assembly process was ensured, hereby, the optimization design model of assembly accuracy reliability was proposed, and the function of the three design model was compared, in order to ensure design method of assembly process.According to the structure and machining requirement of the head of water chamber, description on target object of assembly accuracy was done, the input variable of assembly accuracy solver method was ensured, the solver method of assembly accuracy was given. After the feasibility of measure method on error distribution of combined surface was ensured, combined with the milling experiment, based on the error distribution obtained by the measure method on error distribution of combined surface, experimental verification about the solver method of assembly accuracy was done.According to the connotation about the assembly accuracy reliability and error distribution of combined surface, the evaluation method of assembly accuracy reliability was given, respectively identify the error distribution of combined surface corresponding to the three levels of assembly accuracy reliability, the surface equation of error distribution on combined surface was obtained. Combined with the theory of elastic-plastic deformation and fretting wear and the data obtained from the milling experiment, the criterion in performance stability of combined surface was analyzed, then, to reveal the criterion of assembly accuracy reliability.In order to realize assembly process design method based on assembly accuracy reliability, give the generated assembly order of combined surface and construction method of finite element model, on the basic of which, with examples, do significant analysis of combined surface performance, ensure the optimization order of combined surface, give the method of optimization design of assembly process and give the evaluation method of assembly process.