Abstract
The ASME Y14.5 geometric dimensioning and tolerancing (GD&T) and ISO-GPS (geometrical product specifications) standards define tolerances that can be added to components to achieve the necessary functionality and performance. The zone that each feature must lie within is defined in each tolerance. Measurement processes, including planning, programming, data collection (with contact or without contact), and data processing, check the compliance of the part with these specifications (tolerances). Over the last two decades, many works have been realized by the metrology community to investigate the accuracy, the measuring methods, and, specifically, the measurement errors of fixed and portable coordinate measuring machines (CMMs). A review of the literature showed the progression of CMMs in terms of accuracy and repeatability. However, discrepancies were observed between measurements using different CMMs or operators. This paper proposed a GD&T-based benchmark for the evaluation of the performance of different CMM operators in computer-aided inspection (CAI), considering different criteria related to the dimensional and geometrical features. An artifact was designed using basic geometries (cylinder and plane) and free-form surfaces. The results obtained from the interlaboratory comparison study showed significant performance variability for complex GD&T, such as in the composite profile and localization. This, in turn, emphasized the importance of GD&T training and certification in order to ensure a uniform understanding among different operators, combined with a fully automated inspection code generator for GD&T purposes.
Highlights
Geometric dimensioning and tolerancing (GD&T) (or geometrical product specifications (GPS))is a language of symbols widely used in engineering drawings and computer-generated models to describe, communicate, and determine feature geometry permissible deviations
Inmetrology metrology science, the values true values neverand be all known, and all could potentially have some degree of uncertainty, which is often a function of several variables measurements could potentially have some degree of uncertainty, which is often a function of
We proposed a new GD&T-based benchmark for evaluating the performance of measurement systems in different measurement organizations by considering the uncertainty that can be induced by the operator, the measurement strategy, and the software used
Summary
Geometric dimensioning and tolerancing (GD&T) (or geometrical product specifications (GPS))is a language of symbols widely used in engineering drawings and computer-generated models to describe, communicate, and determine feature geometry permissible deviations. GD&T is an efficient and unambiguous way of communicating the measurement conditions and specifications of a part This language accompanies the entire process chain and helps communicate the part intent and function through the design, manufacture, and inspection. As well, it provides a more precise depiction of part features and focuses on the feature-to-feature relationships. It provides a more precise depiction of part features and focuses on the feature-to-feature relationships Standards, such as ASME Y14.5-2009 [1] and ISO-GPS [2,3,4,5,6,7,8] are comprised of a library of symbols, definitions, rules, and conventions that describe a part in terms of tolerances based on the size, form, orientation, and location. The manufactured part is inspected using a measurement device (such as a coordinate measuring machine (CMM)) and compared with the nominal definition (e.g., a computer-aided design (CAD) file) in order to verify the dimensional and
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