Autonomous calibration method of the zero-difference without using a standard gauge for a straightness-measuring machine

An autonomous method to calibrate the zero difference for the three-point method of measuring surface straightness is proposed A simple cone-disc which can be made by a CNC turning machine is used for the calibration The calibration method is comprised of two steps In the first step the cone-disc rotates around and parallel to three displacement sensors built-in to a holder In the second step the geometrical parameters between the sensors and the cone-disc are simultaneously acquired during each predetermined movement of the sensors and the zero-differences are computed by the proposed algorithm within a few revolutions The conceptual design and the algorithm to realize the proposed method are explained with theoretical analyses and numerical simulations The results of this study are as follows (1) The repeatable accuracy of the zero-difference determination using the proposed method is at the same level of quality as that of the reverse method using the three point method (2) When the zero difference is calibrated using a cone-disc gauge of 200 mm radius and 10 mu m peak height which can be manufactured by a CNC turning machine the shape en or of the objects surface (which is analyzed for its systematic error component and its repeatability error component) becomes less than 05 and 2 mu m at measured lengths of 100 and 200 trim respectively (C) 2010 Elsevier Inc All rights reserved