Revisiting the multi-step method: Enhanced error separation and reduced amount of measurements

Roundness measuring instruments exhibit roundness deviation of the spindle in the 20-30 nm range, and are specified as such. This requires test methods that deliver uncertainties within this range. In order to be feasible such a method must be carried out with a limited amount of measurements within a limited time. In this paper an analysis of the multi-step method for roundness calibration is presented, that analyses the method in terms of its Fourier components and its calculation. From this, an alternative calculation is derived that is as complete and accurate, but requires less measurements to be taken and achieves a higher level of completeness in error separation. Measurements are presented that illustrate the validity of the method and give an estimate of the lower limit of uncertainty that can be achieved, in this case 4 nm. (C) 2015 CIRP.