Investigating the effect of geometric errors of machined parts on the variation and ability of dimensional measurement tools

The non-reproducibility of the measured results of a work piece by reference laboratories is a problem that often causes differences of opinion in production workshops and doubts about the adjustment of production devices with the results provided by laboratories. In this paper, the effect of geometric parameters created by machining on the ability to measure control tools through statistical techniques of quality engineering is investigated, so that first a piece was subjected to drilling and machining, after measurements The exact diameter of the hole with geometric deviation was determined to be cylindrical error to 0.01 mm. Then it was examined with two common measuring systems of air gauge and coordinate measuring machine (CMM) and the capability of the instruments was calculated as follows through the mini-tab software. Capability of air gauge (Cg) in measuring the diameter of hole was 0.27 and capability of CMM device in controlling the said diameter was 0.28. After removing the scattering caused by geometric parameters to calculate the ability of measuring instruments, The power of the instruments was improved to 1.20 in the wind gauge and 1.05 in the CMM and finally, by removing or reducing the geometrical error of the work piece, It should be noted that in this study, after removing the error of workpiece the lack of repeatability in the air gauge increased from 74% to 16.66% and in the coordinate measuring machine (CMM) from 70.80% to 19.13%.