数字化铸造砂型五轴联动成形控制技术研究

Control technology of five-axis linkage forming for digital casting sand mold

数字化无模铸造具有污染少、周期短、成本低等优势,越来越多的复杂薄壁铸件铸造砂型采用五轴联动高速成形。推导了B-C双摆头结构五轴联动旋转刀具中心(RTCP)砂型成形运动学模型。分析了五轴联动矢量速度计算方法及速度波动机理,根据各轴速度与位置变化率比值的约束关系,提出了通过单轴速度前瞻控制实现五轴联动高速加工整体速度控制方法,并给出了前瞻阈值的计算方法。基于开放式控制系统,开发了五轴联动旋转刀具中心正逆解程序,并进行了叶轮砂型五轴加工及Z轴前瞻控制实验。结果表明,所设计的旋转刀具中心正逆解及提出的单轴前瞻控制策略是砂型五轴联动高速成形的有效控制方法。

Digital forming technology without pattern casting has the advantages of less pollution,short cycle and low cost.More and more casting sand molds of complex and thin-walled castings are formed by using five-axis linkage high-speed machining.The kinematical model of five-axis linkage with B-C double head for sand mold forming was derived on the basis of Rotation Tool Center Point(RTCP).The computing method of vector speed and the mechanism of speed fluctuation were analyzed.According to the constraint relationship between the ratio of each axis speed and the ratio of each axis position changing,the scheme that the overall speed control of five-axis linkage high-speed machining realized by single axis speed look ahead control was proposed,and the calculation method of look ahead threshold was given.Based on the open control system,the forward and inverse kinematics solutions of five-axis linkage RTCP were developed.The experiments including five-axis machining of impeller sand mold and look ahead control of Z axis were conducted.The experimental results showed that the proposed forward and reverse kinematics solutions of RCTP and the single axis look ahead control strategy was an effective control method for sand mold five-axis linkage high-speed forming.