| Despite all efforts made by the manufacturers of coordinate measuring machines to guarantee maximum precision of the measuring results, the measuring machines themselves exhibit uncertainty.
As described in Unit 7 (Structure of Coordinate Measuring Machines), the measuring uncertainty of a coordinate measuring machine is affected by the guideways, bearings and drives and in particular by the accuracy of the length measuring systems of the moving axes.
To achieve very high accuracies, certain very accurate coordinate measuring machines are tested by the manufacturers prior to delivery in each axis position. With the machine running, these deviations, depend on the axis position, are compensated for by means of a mathematical correction.
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