A method for detecting alignment deviation on a thread-measuring instrument

Abstract

Alignment deviation is an important factor affecting measurement accuracy in screw thread measurement. It needs to be detected and controlled to ensure the accuracy of relative thread parameters. The influence on pitch diameter caused by the alignment deviations of workpiece and probe is analyzed in this paper. In order to detect and control the alignment deviation, a vision detection method for the probe tip points is proposed, which integrates the detection of corners and edges and the prediction of motion. Then the X-axial rotation deviation is calculated by tracking the tip points both up and down. The result of tests demonstrates that the detection accuracy of the X-axial rotation deviation is 0.0654° with the background changing during the probe movement. The repeatability of the test procedure is ±0.16%, which proves the detection method is adequately qualified for application.