The Static/ Dynamic Performance Analysis And Structure Optimization Of The High Speed Horizontal Machining Centers

In the machining process, vibrations are the main cause of lowering machine tools accuracy. The severe vibrations even affect the operability of the machine tools and reduce its life time. Structure design and layout of the parts directly affect the precision of the machine tool. Under the premise of reducing the machine tool mass, how to ensure or improve the static and dynamic performance of the machine tool by structure optimization has become a research focus. Relying on "Science and Technology Project of Twelfth Five-Years National Support", High-speed Horizontal Machining Center(HMC-63h) is studied in this paper. By theoretical model analysis, finite element modeling and other methods, the effects of the main structures in HMC-63 h including column, saddle and bed to static and dynamic performance of the machine tool are analyzed. Then the structure optimization methods about these structure parts are proposed and the structure of these parts are optimized. The main contents include:(1) According to structural dynamics theory, the dynamic response analysis of multi-DOF damped system is completed. Then finite element equivalent dynamics model of the machine tool is built by using spring- damping unit to simulate sliding rail joint surface and bolt joint surface between the column and bed. These researches provide the basis for the static and dynamic performance analysis of the machine tool and its structure optimization.(2) Through modal analysis and harmonic response analysis, the key structure part to affect the dynamic performance of the machine tool is identified as column. Taking the column structure as optimization object, a structure optimization method is proposed based on topology optimization, ribs form selecting and layout, and size optimization. Then a new column structure with W-shape ribs is designed. By comparing static and dynamic performance of the single column and the machine tool before and after optimization, the effectiveness of optimized structure is verified.(3) Based on sensitivity analysis, the size parameters which have a great influence to dynamic performance of the saddle structure are gotten. Then these size parameters are optimized by response surface optimization method. The analysis results show that the mass of the saddle is reduced by 7% on the premise of not affecting the static and dynamic performance of the machine tool. The new saddle structure effectively reduces the energy consumption of machine tools, and improves the flexibility and acceleration performance of moving parts system in the machine tool.(4) Unit structure optimization method of the machine bed is studied. Firstly, according to the existing conclusions about unit structure optimization and analysis, multi-objective optimization of the bed structure is completed. Then, deficiencies of unit structure optimization method are analyzed. Based on extraction, analysis and optimization of the unit structure, a two-level optimization method of the unit structure is proposed about the machine bed. Finally, the multi-objective optimization results and two-level optimization method of the unit structure is validated in single machine bed structure and the machine tool. The effectiveness of different optimization bed structure projects is evaluated.