Optimal inspection strategy planning for geometric tolerance verification

Abstract

Two features characterize a good inspection system: it is accurate, and compared to the manufacturing cost, it is not expensive. Unfortunately, few measuring systems posses both these characteristics, i.e. low uncertainty comes with a cost. But also high uncertainty comes with a cost, because measuring systems with high uncertainty tend to generate more inspection errors, which come with a cost.In the case of geometric inspection, the geometric deviation is evaluated from a cloud of points sampled on a part. Therefore, not only the measuring device has to be selected, but also the sampling strategy has to be planned, i.e. the sampling point cloud size and where points should be located on the feature to inspect have to be decided. When the measuring device is already available, as it often happens in geometric measurement, where most instruments are flexible, an unwise strategy planning can be the largest uncertainty contributor.In this work, a model for the evaluation of the overall inspection cost is proposed. The optimization of the model can lead to an optimal inspection strategy in economic sense. However, the model itself is based on uncertainty evaluation, in order to assess the impact of measurement error on inspection cost. Therefore, two methodologies for evaluating the uncertainty will be proposed. These methodologies will be focused on the evaluation of the contribution of * Correspondig Author. Tel +39 02 23998530. Fax +39 02 23998585.Email addresses: giovanni.moroni@polimi.it (Giovanni Moroni), stefano.petro@polimi.it (Stefano Petrò) Preprint submitted to Elsevier January 9, 2015 the sampling strategy to the uncertainty. Finally, few case studies dealing with the inspection planning for a Coordinate Measuring Machine will be proposed.

Performance Verification of a 4-Axis Focus Variation Co-Ordinate Measuring System

“…The design of the artifact depends on the blank which is a solid aluminum cylinder having a diameter equal to 80 mm. The overall size of the artifact is 90×80×80 mm 3 . Finally, it should be noted that the artifact shape is not as important as the position and configuration of the steel spheres.…”

“…In 3-axis configuration, one can use the maximum measuring volume 100×100×100 mm 3 . The effective measuring volume of this configuration is illustrated in Fig.…”

“…1b shows the effective measuring volume in this configuration. Finally, it is possible to use the complete 4-axis configuration of the machine, as the four axes working together simultaneously allow a complete measurement of the part by means of a suitably designed measurement strategy [2], [3]. Due to this reason, the conventional measuring volume definition is changed to a new one.…”

An Exploration into Measurement Consistency on Coordinate Measuring Machines

“…However, the position of those points is also significant because the optimal measurement strategy is highly dependent on form [18]. Accordingly, strategies can be categorised according to the importance they place on the actual geometry produced [19], as described in the subsections below.…”

Simulation of Laser Triangulation Sensors Scanning for Design and Evaluation Purposes

“…Basically, for measurement systems, unwise strategy planning can be the largest uncertainty contributor [22]. Besides, parts verification can be a significant cost, so a proper sampling strategy becomes a must.…”