||Uncertainty Assessment Using Multiple Measurements on Coordinate Measuring Machines: Application to a Master Ring and a High Precision Cylinder
||Tosello, Guido (DIMEG, Univ. of Pado)
||Technical University of Denmark, DTU, DK-2800 Kgs. Lyngby, Denmark
||The present work contains a study related to traceability and uncertainty assessment using coordinate measuring machines (CMMs) according to the principle of un-calibrated work pieces.
Investigations were based on the calibration of two very accurate objects: a high precision ceramic cylinder and a 100 mm master ring.
An experimental procedure, described in draft ISO/TS 15530 part 6 Uncertainty Assessment Using Un-Calibrated Work Pieces and a Multiple of Measurement Strategies, was applied to determine the measurement uncertainty for the specific measuring tasks. The method is based on a multiple of positions of objects (the item to be measured and the standards) on the measuring volume of the CMM and a repetition of the measurements in order to determine the relative standard deviation.
The expanded uncertainties obtained are: U=1.1 µm on 122 mm diameter, U=1.1 µm on cylindricity, U=0.2 µm on flatness and U=2.8 µm on squareness (ceramic cylinder).
A measurement method using both multi-step and reversal technique was developed in order to increase accuracy on roundness measurements using coordinate measuring machines. A software to calculate least square circle, form error, Gaussian filtering and to plot results was developed using a spreadsheet.
Elimination of systematic errors from both the machine and the probe was obtained with accuracy improvement of 300%. A comparison of results from CMM and roundness tester shows agreement of the form error on roundness within 0.020 µm. Then an experimental application of the draft ISO/TS 15530 part 6 was used. Expanded uncertainty obtained are: U=0.64 µm on 100 mm diameter, U=0.064 µm on roundness. Comparison with results of the Czech Metrological Institute (CMI) research shows agreement within the uncertainty limits.
Creation date: 2006-06-22
Update date: 2007-02-24