No abstract

This paper proposes a quick and efficient methodology of uncertainty estimation on measurement results provided by an articulated arm coordinate measuring machine (AACMM). The methodology is highly adapted to industrial applications—a frequent use of these devices—but can also be performed in laboratories. The study stems from an actual need among coordinate measuring arm users to estimate the uncertainty associated with their equipment in specific conditions on the shop floor. It is important to mention that no simple and quick test exists currently to estimate the measurement uncertainty of results obtained with an AACMM in the conditions of the measurement site. In fact, the guidelines and studies addressing measuring machines propose protocols to verify performance or to evaluate uncertainties associated with measurement results, but these protocols are laboratory-type tests (carried out after purchase, re-calibration, etc) and usually take hours to complete.

Abstract. Monte Carlo method have been introduced in metrology in the 1990's and integrated in the GUM (Supplement 1) in 2008. This method is more and more used. Typically the users of this method realize a complete simulation in one step, like the GUM, one step for one model. This is unfortunate, the simulation loses its physical sense. The study aim is to present a multi-level Monte Carlo approach which allows being near of the reality of the measurement process. Two applications are developed: evaluation of the uncertainties on CMM and on AACMM. This principle has been developed with CETIM for COFRAC accreditation on CMM for gear measurands. The simulation is divided into two principle stages, namely the first is the comprehensive evaluation of possible changes in the geometry of the CMM and the second step, directly related to the measure of the piece, is the evaluation of the analyzed measurand. For AACMM, same principle is realized but the first level is divided into three sub-levels. The division into several levels has many advantages. Indeed, it makes it easier to understand the key sources of uncertainty and thus optimize processes.

In the present study, the influence of sandblasting condition (working pressure) on surface texture is modeled, relying on a multi-scale approach and statistical analysis. To improve the correlation modeling between the process condition and surface texture, special effort is made to identification of an optimal parameter set, including 3D roughness parameters, cut-off lengths, filter types and model types. A power law relationship is identified between the pressure and Sdq computed with a cut-off length of 120 µm using a low-pass filter. Experimental and theoretical arguments are provided for justification. SCANNING 38:191-201, 2016. © 2015 Wiley Periodicals, Inc.

In order to verify the performance of articulated arm coordinate measuring machines, the standards/guidelines that address this topic require the use of different length artefacts. For instance, the volumetric test of ISO 10360-12:2016 requires measuring five calibrated lengths in seven directions (three horizontal, three diagonal and one vertical). If a ball bar is used to perform the test with each sphere measured with five points, then the test requires measuring 1050 points (7 directions × 5 lengths × 2 spheres × 5 points × 3 repetitions).The aim of this paper is to optimize this type of test and adapt it to industrial environments, in terms of ergonomics and time of measurement. For this purpose, two solutions merging the concept of segmented ball bars with the concept of kinematic seats are proposed. The first solution involves using a passive self-centering probe and a regular segmented ball bar (with joining spheres). The second novel solution involves replacing the joining spheres of the ball bar by spherical mounts containing kinematic seat inserts and a regular spherical probe. The kinematic seats in both solutions are designed in a way to optimize their rigidity, machinability and their uncertainty of measurement. Both proposed solutions reduce considerably the time of measurement. In addition, it will be demonstrated in the paper that the first solution presents the advantage of decreasing the uncertainty of measurement whilst the second solution might increase it lightly, compared to a regular ball bar measured with a regular spherical probe.