Online volumetric error compensation for micro-CMMs using embedded multi-DOF (degree-of-freedom) measurement systems based on Abbe and Bryan principles

The measurement accuracy of micro coordinate measuring machines (micro-CMMs) is limited by the volumetric errors. In this paper, the volumetric errors caused by geometric errors are analyzed, and the volumetric error model is built firstly, which is based on Abbe and Bryan principles. Correspondingly, this article proposes embedded multi-DOF measurement systems (EMDMS) for global volumetric error online compensation, which is consist of laser interferometers and autocollimators. The EMDMS enables real-time simultaneous measurement of 15 straightness and tilting errors. While the acquired error data are integrated into the developed volumetric error model, the control unit, equipped with three PID controllers, leverages the EMDMS data and the error model to achieve online error compensation of a micro-CMM. A Zero-class gauge block was tested based on ISO 10360–2 to evaluate the effectiveness of the EMDMS and volumetric error model. After volumetric error compensation, the standard deviations and indication errors of the length measurements in different directions were reduced by more than 90 % and 94 % respectively, and the measurement expanded uncertainty along Y direction is 216 nm (k = 2). Furthermore, the standard measurement uncertainty of the EMDMS evaluated with values of 50 nm, 49 nm, and 58 nm in the X-, Y-, and Z-directions, respectively. The proposed method and system can be used in the volumetric error compensation of micro-CMMs effectively.