A study on dynamic error of the measurement machine with low stiffness

The higher measuring accuracy and velocity of the coordinate measuring machine are required for shorter cycle time for modern manufacturing industry. However, the increments in measuring accuracy and velocity of CMM applications are limited by the low stiffness components which cause the complicated deformation and dynamic errors. According to the structural characteristics of a special structure coordinate measuring machine, a non-rigid body model is established and the error compensation formula is derived. Further more the dynamic model of this CMM is established by Lagrange energy theory. Based on the models of this CMM, the systematic analysis method of the measurement error is proposed. In this paper, the measurement errors of CMM are studied in an integrated theoretical and an experimental approach. We use a laser interferometer to measure the measurement errors of this CMM under static deformation, and the dynamic errors are measured by different motion parameters of CMM. The experiment results show that the measuring errors caused by the limited stiffness of the components of the measuring machine can not be neglected. By software compensation, the measurement error can be reduced from 8.9mum to 2mum. The outcome of the dynamic errors experiment reflects the influence of dynamic errors under different motion parameters. Hence, the result is useful to study the measurement for decreasing and restraining the dynamic errors and to present a clearer and deeper knowledge of compensation for dynamic errors.