横梁蠕变松弛对龙门镗铣床运动精度可靠性的影响建模

Modeling of Influences of Beam Creep Relaxation on Kinematic Accuracy Reliability of Gantry Boring-milling Machines

针对横梁蠕变变形对龙门镗铣床精度保持性的影响问题,建立了一种龙门镗铣床运动可靠性评估模型。采用有限元软件对横梁残余应力进行多工序连续建模仿真,并通过盲孔法测试验证了有限元模拟的有效性;根据横梁导轨与滑枕座间几何误差的表征关系构建了龙门镗铣床的几何精度退化模型,利用蠕变模拟数据确定y向几何误差退化轨迹;结合机床空间位置误差模型和误差退化轨迹建立了机床运动可靠性评估模型,进而实现对服役期的龙门镗铣床运动可靠性的预测,以及对不同横梁应力状态下运动可靠性的比较评估。结果表明,横梁蠕变变形导致机床运动精度可靠性呈幂律函数形式衰退,且在时效前较大应力下机床运动可靠性降低更明显。

Aiming at the influences of the beam creep deformations on the accuracy retention of the gantry boring-milling machines,a kinematic reliability assessment model of the gantry boring-milling machines was established.The multi-process continuous simulations of the beam residual stress were carried out by utilizing finite element software,and the validity was verified by the blind hole method.The geometric accuracy degradation model of the gantry boring-milling machines was constructed based on the error representation relationship between the beam guide and the ram seat,and the degradation trajectory of y direction geometric errors was determined by the creep simulation data.Combining the machine tool spatial position errors and the error degradation trajectory,the kinematic reliability assessment model was established to predict and assess the kinematic reliability of the gantry boring-milling machines under different residual stress states during the service period.The results show that the beam creep deformations cause the kinematic reliability of machine tools to decline as a power law function,and the decrease is more obvious under the greater stress before aging.