DETERMINATION OF COORDINATE MEASURING MACHINES ACCURACY CHANGES MADE BY DIFFERENT NODES DENSITY IN CAA MATRIX

Adam Gaska, Jerzy Sladek, Ksenia Ostrowska, Robert Kupiec, Marcin Krawczyk, Wiktor Harmatys, Piotr Gaska, Maciej Gruza, Danuta Szewczyk, Renata Knapik, Artur Kmita

Abstract

Advances in modern manufacturing techniques implies more efficient production but also new tasks for coordinate metrology and producers of Coordinate Measuring Machines (CMMs). Main aim here is accuracy improvement. The solutions used regarding CMM construction are easy and it is hard to improve it now. So accuracy improvement is done mainly using sophisticated mathematical algorithms that are responsible for correction of relevant errors. Different types of errors could be compensated, including: probe head errors, machine dynamics errors and most of all machines geometrical errors. Almost all coordinate measuring machines produced nowadays are equipped with geometrical errors compensation matrix known as CAA matrix (Computer Aided Accuracy).<BR />CAA matrices are based on grid of reference points (nods) in which certain values of components of geometrical errors are experimentally determined. Values between this nodes are estimated using simple interpolation methods. Theoretically, the more dense is the grid on which CAA matrix is described, the better is the accuracy of the machine on which the matrix was used. On the other side, increased number of nods implies bigger costs of matrix determination connected with greater amount of time and workload.<BR />This work presents experiments aiming in determination of CAA matrix using LaserTracer system done for different densities of matrix nodes. The relations between maximum permissible errors obtained on machine using matrices with different densities of nodes will be shown. Authors would also try to answer the question how to determine the most appropriate nodes density regarding the ratio of time spent for matrix creation and obtained accuracies.

Keywords

geometric compensation, CAA, geometric error, machine mapping, CMM

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DOI

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IMEKO TC

TC14 - Measurement of Geometrical Quantities

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