基于切削动力学及其不确定特性的数控机床结构参数分析优化

Analysis and optimization of parameters of machine tool in structure design based on the cutting dynamics with uncertainty

针对传统数控机床结构设计中较少考虑切削动力学及其不确定特性的问题,提出了基于切削动力学约束和不确定因素的影响,根据目标切削深度对结构进行优化设计的方法。分析切削动力学特性,根据颤振频率分布和整机模态实验确定限制切深的关键部件,以其外部轮廓壁厚和内部筋板壁厚为对象,进行参数灵敏度分析以确定设计参数。将最小临界切削深度与目标切削深度的差值转化为结构动柔度的修改量,在质量、静刚度等条件的约束下,通过对局部结构的修改,在保持质量基本不变的情况下,满足了生产率要求的目标切削深度,并以一台数控加工中心的结构优化设计为例进行了验证。

A method for machine tool design parameters optimization was presented to obtain a desirable cutting depth in the milling process,under the constraints of cutting stability and its uncertainty,which have been rarely considered in the traditional design. According to the chatter frequency distribution and the modal tests results,the key influential component of the machine tool which determines the minimal cutting depth was located. Targeting at the thickness of external contour and internal rib of the component,the sensitive design parameters to be modified were selected according to a sensitivity analysis. The difference between the desirable cutting depth and actual cutting depth was converted to an amount for structural dynamic flexibility modification. With the minimum local structural modification,the desirable cutting depth was obtained to meet the requirement of material removal rate（ MRR） under the constraint of keeping unchanged the static stiffness and the static weight. The method was verified via the optimization design of a CNC machining center.