FEM Study on the Dynamic Effects of CMM Geometric Errors

Geometric errors are seldom considered the generations of CMM dynamic errors. This paper presents the dynamic effects of the geometric errors of CMM in fast probing, and investigates the properties with Finite Elements Method (FEM). The FEM model was composed of CMM moving bridge and its guide way. Presuming CMM guide way as an ideal rigid geometry, then angular errors were generated by the rotations of guide way around a corresponding coordinate axis, while translation errors came from the translations of guide way. Thus the 6 geometric errors on each guide way were completely decoupling and the corresponding dynamic effects were studied respectively. Analyses show that the angular errors around Y and Z-axes, Y(x) and Z(x), can induce remarkable dynamic effects at probe tip, especially in a CMM with low stiffness air bearing.