Title: Influence of eccentricity and axis tilt on circularity and cylindricity assessments

Authors: M.S. Shunmugam, N. Venkaiah

Addresses: Department of Mechanical Engineering, Indian Institute of Technology Madras, Chennai-600036, India. ' Department of Mechanical Engineering, Indian Institute of Technology Madras, Chennai-600036, India

Abstract: Circular and cylindrical features are commonly present in the engineering parts. After manufacturing, measurement of these features can be done using either form measuring instruments or coordinate measuring machines (CMM) and form error value is evaluated with reference to a suitable feature. Misalignment between instrument centre/axis and the actual centre/axis of the feature influences the form error values obtained. Though analysis of form measurement using a truly circular part is reported in literature, an attempt is made in this paper to develop mathematical equations for carrying out simulation on truly cylindrical parts with misalignments and to select suitable reference features for form and CMM measurements. It is established that form measurement requires limacon and limacon-cylinder references, while circle and circular-cylinder references are suitable for CMM measurement for circularity and cylindricity evaluation respectively. Wider ranges of misalignments are considered to bring out the robustness of the references. The effect of misalignment is particularly important, when the tolerances are tighter as in precision manufacturing and metrology.

Keywords: circularity; cylindricity; eccentricity; axis tilt; limacon; circles; limacon-cylinder; circular-cylinder; circular features; cylindrical features; form error values; simulation; misalignment.

DOI: 10.1504/IJPTECH.2010.031656

International Journal of Precision Technology, 2010 Vol.1 No.3/4, pp.234 - 250

Published online: 16 Feb 2010 *

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