Performance of Articulated Arm CMM using Virtual Spheres Gauge and geometry deviation analysis

Abstract

This work proposes a new methodology for testing Articulated Arm Coordinate Measuring Machines (AACMM) performance using the Virtual Spheres Plate (VSP) gauge to evaluate the geometric characteristics during measurement. An aluminum 400 mm x 400 mm VSP having 16 pyramidal inserts with 4 conical holes at each was used to determine the point coordinates of the hole centers. The test was performed in a Romer Arm 100 AACMM using a 6 mm ruby-made spherical stylus with a rigid probe. The gauge was positioned in three different locations and positions in AACMM work volume and the points were determined three times in each combination. An algorithm was developed in MatLab softtware to calculate geometric figures with the points determined, based on least squares method. The geometric deviations of straightness and flatness were determined to characterize the performance of the machine in respect to this type of measurement. The results were compared with ones from GPad AACMM software and with NIST reference algorithm, proving suitable to AACMM evaluation. This test can give additional information about the performance and can be used to compare different measuring machines.