Improvement of measurement resolution of a mechanical touch-trigger probe method for static radial runout measurements based on digital image correlation

Despite many of the reported attempts to make continuous improvements in metrology, the probing system is still the workhorse up to present, and the production metrology employing a touch-trigger probe system to achieve the accuracy of the sub-micron level is another emerging area. In this paper, an improved mechanical trigger probe-based method has been proposed for measuring the static radial runout overcoming the measurement resolution limitations. The improvement can be realized by using digital image correlation (DIC) method. Using this method, a novel measurement system was designed and setup. The developed system is based on a traditional mechanical trigger dial indicator with a resolution of 10 mu m and a simple DIC optical amplification setup. Then, the system was exerted on an example of a high-precision hydraulic spool with known radial runout. Experiment results have shown that it can improve the measurement resolution limit of the traditional indicator to a higher level. The measurement resolution was improved to the sub-micron level. To further add confidence to this method, the results obtained by using the established measurement system were compared to those obtained by using the precision-manufactured but expensive LVDT displacement sensor and showed that they had closely matched levels of accuracy. This kind of system offers such advantages as low cost, simple construction, and good accuracy.