An approach to estimate the sample size based on surface roughness for flatness error measurement using CMM

R. Raghunandan, P. V. Rao

Abstract

The present day manufacturing environment requires accurate inspection of both dimension and form while minimizing the cost and time of inspection. Flatness error is an important form tolerance that is used for the control of machined surfaces. The evaluation of flatness error depends on a variety of factors such as selection of sampling plan - sample size and sample point locations, the method of evaluating the form error and the nature of the manufactured surfaces amongst which the sample size is very critical. In most cases the sample size is decided based on the experience of the inspector or is randomly selected which may not be the ideal methods if a high degree of accuracy is required for the evaluation of the flatness error. Investigations carried out reveal that the surface roughness influences the accuracy of inspection and can be used as a parameter for determining an initial sample size for the determination of flatness error. The experimentation involved the inspection on surfaces with different roughness and calculation of the flatness error was based on the Minimum Zone Method. The percentage discrepancy of measurement computed from experimental data is then used to determine the number of sample points (sample size).

Keywords

Coordinate Measuring Machine (CMM); flatness error; sample size; surface roughness; Minimum Zone Method

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IMEKO-TC14-2007-17.pdf

DOI

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IMEKO TC

TC14 - Measurement of Geometrical Quantities

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