The use of virtual circles gauge for a quick verification of Portable Measuring Arms Daniel González-Madruga 1 , Eduardo Cuesta 2,a* , Hector Patiño Sanchez 2 , Joaquín Barreiro 1b and Susana Martínez-Pellitero 1 1 Dept. of Mechanical, Informatics and Aerospace Engineering, University of León, Campus de Vegazana, León 24071, Spain. 2 Dept. of Manufacturing Engineering. University of Oviedo, Campus de Gijón, Asturias 33203, Spain. a ecuesta@uniovi.es, b joaquin.barreiro@unileon.es Keywords: Virtual circles; AACMM evaluation; Accuracy; Evaluation gauge Abstract. Portable Measuring Arms or Articulated Arm Coordinate Measuring Machines (AACMMs) unique characteristics bring flexibility to the inspection task and allow outside laboratory measurements. However, still a few works study their metrological behavior, uncertainty or assessment. In fact, AACMM assessment involves time consuming and expensive processes mainly inherited from CMM field. A virtual circle gauge similar to ball bars and a methodology based on international standards are proposed in order to simplify the evaluation test. Additionally, two metrological laboratories have evaluated different AACMM models with this gauge. Also, two gauge lengths (distance between circles) have be included in this study. Results have proved that virtual circle gauges are suitable to evaluate AACMMs and tested the influence of distance between virtual circles. Introduction Over the last decade, AACMMs have given important productivity and flexibility improvements in inspection tasks where the highest level of accuracy is not required. Portability and flexibility achieved with AACMMs characterize their performance but also affect to their metrological behavior and measurement uncertainty. Calibration and evaluation principles have been inherited from CMM field even though AACMMs require new approaches according to their unique characteristics. Authors works presents some basis points such us kinematic model, gauges, calibration positions, optimization algorithm... Nevertheless, AACMMs metrological behavior still has to be studied. Several calibration and evaluation methods have been proposed so far. Santolaria et al. [1] presented a complete calibration method with a ball bar gauge where the error terms, volumetric performance and point repeatability are minimized by least squares. Furutani et al. [2] also measured a two-ball bar in several locations. Kovac et al. [3] designed a linear instrument for AACMM calibration. Several standards have presented evaluation methods, but they are time consuming processes. ASME B89.4.22 [4] defines an evaluation method based on three tests to determine the AACMM performance with a ball bar and a conic holes gauge. VDI/VDE 2617 part 9 [5] evaluates AACMMs with three tests, a ball bar and conic holes as well. Spheres are commonly used in scientific or industrial field especially in CMM, Cauchick-Miguel et al. [6]. However they are uncomfortable features for manual operating with AACMMs. Regarding conic holes, they are adapted to AACMM manual operating since the sphere of the stylus is easily placed on the cone and, theoretically, the same point is reached each time. Standards and some authors take advantage of this particular characteristic for repeatability evaluation of a single point error when varying the AACMM configuration, ASME B89.4.22 [4] and VDI/VDE 2617 part 9 [5]. Gao et al. [7] calculate the AACMM kinematic parameters by mean of neural networks and conic holes. Key Engineering Materials Vol. 615 (2014) pp 70-75 Online available since 2014/Jun/30 at www.scientific.net © (2014) Trans Tech Publications, Switzerland doi:10.4028/www.scientific.net/KEM.615.70 All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of TTP, www.ttp.net. (ID: 93.156.84.251-03/07/14,22:00:54)