A Novel Pretravel Error Compensation Strategy for Five-Axis On-Machine Measurement With a Touch-Trigger Probe

Touch-trigger probes (TTPs) have been commonly utilized in on-machine measurement (OMM) by virtue of their low cost and high repeatability. The pretravel error (PTE) compensation of the probe is one of the critical issues in improving OMM precision. The majority of existing studies on PTE compensation in five-axis OMM adopt the same strategy as in three-axis OMM. Thus, the discrepancies between the two measurement processes and PTE compensation principles are ignored, which results in poor compensation accuracy for the five-axis measured results. In this article, a novel PTE compensation strategy is presented to accurately compensate for the five-axis OMM results. Due to the limitations of the PTE map formed by the calibrated positions on the standard sphere for application in five-axis measurement, a PTE map represented by the touch positions on the stylus tip is developed. As a result, the exact mapping relationships between the touch positions on the stylus tip and the PTEs in five-axis OMM can be constructed. Then, the calculations of the PTE compensation component (PTECC) in three-axis OMM and five-axis OMM are discussed and compared. Specifically, the positioning deviations of rotary axes are also considered in the proposed strategy to compensate for their influence on the measured results during the five-axis measurement. Finally, impeller inspection tests are performed to validate the effectiveness of the proposed compensation strategy for five-axis OMM, and more than 20% inspection precision improvement is observed.