Monte Carlo method for evaluating the uncertainty of roundness measurements on a CMM – a Python implementation

Coordinate measuring machines (CMMs) are leading instruments in production metrology, due to their accuracy, precision, flexibility and level of automation. They are essentially based on sampling of coordinates of points on manufactured pieces, and can virtually measure any tolerance indicated on the drawing. Among different form tolerances, roundness tolerance is often present in technical documentation, when in the presence of centrosymmetric objects. CMMs usually show high quality metrological characteristics, but, as well as every other instruments, they are affected by a certain amount of measuring uncertainties, and it is generally a good practice relying on the Monte Carlo technique to numerically estimate the uncertainty in a measuring process based on the use of a CMM. This report presents a developed model for the evaluation of measurement uncertainty in the process of measuring roundness on a CMM. The described model is used with concrete measuring machine and concrete workpiece.