Machinery's Handbook, 31st Edition
GD&T and CAD Models 635 GD&T and CAD Models.— ASME Y14.5-2018 and all earlier editions are usable on mod- ern CAD systems. However, the primary concepts are still communicated visually among design, manufacturing and quality stakeholders via annotation applied to engineering drawings, be they on paper or depicted on a computer monitor. Effectively, there is no difference between specifications communicated manually on paper using a pencil and those applied to a drawing on a CAD system, the latter being for all practical purposes an electronic drawing board. As such, utilization of the tolerancing information still requires that a person read the specifications, interpret them and manually apply the information in manufacturing and/or quality systems. That manual process has begun to change with the introduction of ANSI/ASME Y14.41-2012, Digital Production Definition Data Prac - tices, and its international version ISO 16792:2006, Digital Production Definition Data Practices.
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Fig. 15. Visual Response to a Tolerance Query on a 3D CAD System Compliant with ASME Y14.41-2012
These standards define use of ASME GD&T practices and ISO GD&T practices, respectively, in a digital environment where specifications are embedded directly into the product definition data set as part of product lifecycle management (PLM). Embedded GD&T is generally called “eGD&T” (electronic geometric dimensioning & tolerancing). Once incorporated into the data set, the specifications can be selectively queried for visual display as needed on a computer screen or an engineering drawing, see Fig. 15. Perhaps more importantly, the embedded tolerancing information can be directly accessed by software for tolerance analysis, process planning, or any other applications designed to utilize the geometric and tolerancing information as part of product lifecycle management. As these standards are adopted by CAD vendors and fully implemented, their promise is for a more expedient, more accurate design and analysis process.
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