考虑机床动态性能的床身元结构二次优化方法

Two-level Optimization Method of Bed Unit Structure Considering Dynamic Performance of Machine Tool

通常在机床零件的拓扑结构形式确定以后,单纯的尺寸优化往往难以取得较好的效果。以某卧式加工中心的床身结构为研究对象,提出了一种在元结构优化分析的基础上对结构整体进行二次优化的方法。首先根据床身结构特点提取其元结构进行优化分析,按优化得到的圆形与椭圆形出砂孔尺寸参数对床身结构进行重新设计。然后采用响应面优化方法,将元结构分析的尺寸参数在床身整体结构中进行进一步优化研究。分析表明,在结构质量变化极小的前提下,单纯的元结构优化设计的床身能够改善结构单件及整机的动态性能,但改善幅度较小;而床身整体结构二次优化后其基频提高的幅度约是前者提高幅度的3倍,同时使得整机参考点在X方向的最大响应幅值降低55.2%,Y方向降低83.9%,Z方向降低82.8%。

It is often difficult to achieve further optimization results of machine tool parts in terms of sizes parameters after the topology structure of these parts are determined. Taking the machine bed structure of a horizontal machining center as an object, a two-level optimization method of the unit structure was proposed, which was based on the analysis and optimization of unit structure, to optimize the whole machine tool bed. Firstly, according to structural features of this machine tool bed, different unit structures were analyzed and compared, and then the round and oval sand hole with original sizes parameters were chosen as the most suitable units to redesign the bed structure. After that, based on response surface method and taking the whole machine tool bed as optimization goal, the second-level optimization of unit structure in terms of sizes parameters was achieved. On the premise of minimal change of bed mass, the results of the analysis demonstrate that the two-level optimization method achieves better dynamic performance of machine tool compared with single-level optimization method which only focuses on the optimization of unit structure. To be more specific, the former method can increase the fundamental frequency of this machine tool bed 3 times than the latter method. Besides, when the former method is applied, the biggest resonance peak of this machine tool is reduced by 55.2% in X-direction, 83.9% in Y-direction, and 82.8% in Z-direction.