Develop an awareness of Dimensional Engineering concepts and explain how the techniques are used to understand, control, and help reduce variation in the overall vehicle build process.Introduction to the Build Tolerance Procedure.Provide an overview of the Variation Simulation Modeling (VSM) process and how it is used to predict variation in the vehicle.Provide an introduction to Geometric Dimensioning and Tolerancing (GD&T), the ASME Y14.5M-1994 Standard including the GM Global Addendum and how the concepts, symbols and terms of GD&T are used in the engineering process.
Dimensional Engineering
Dimensional Engineering is a sub-process within the overall vehicle development cycle, key to achieving robust designs and controlling product definition.The concept starts with “bubble-up” and continues through the entire Four Phase Vehicle Development Process. The “Team Concept” is an integral part of the GMTG Dimensional Engineering approach.
What is GD&T?

Geometric Dimensioning & Tolerance is an international graphic engineering language designed to allow designers and engineers to “say exactly what they mean” on engineering drawings. The concepts, symbols and mathematical structure of GD&T provide a precise and logical way to describe the manufacturing tolerance zones that are applied to individual features or groups of features on parts or assemblies.
What is ASME Y14.5M-1994?

The ASME Y14.5M-1994 is the latest revised issue of the common Industrial Standard on dimensioning and tolerancing. The Standard establishes uniform practices for the dimensioning and tolerancing of engineering drawings and related documents. All GD&T rules, concepts, and practices are contained within the current Y14.5M Standard and the GM Global Addendum.
Why a GM Global Addendum?

The GM Global Addendum was written to address and/or clarify concepts and practices described within the ASME Y14.5M-1994 Standard. Sections 1-6 of the addendum represent the consensus of the US Car GD&T Team and have been adopted by GM, Ford, and Chrysler. Sections 7&8 apply specifically to General Motors.
The addendum replaces section A91 of the current GM Drafting
The goal of GD&T is to improve communication !!

• Objectives
• Dimensional Engineering Concept
• ASME Y14.5M-1994 and GM Global Addendum
• Video - Introduction to GD&T
• The Language of GD&T
• Why Use GD&T ?
• Engineering Drawings - General Review
• Basic Rules and Definitions
• Datum Function & Datum Reference Frames
• Datum Planes, Features and Simulators
• Datum Target Areas, Lines, Points and Partial Datum Surfaces
• Feature Control Frame Elements
• Variation Simulation Modeling (VSM)
• Tolerances of Form
• Tolerances of Orientation
• Tolerances of Runout
• Tolerances of Profile
• Tolerances of Location
Why Use GD&T ?
Manufacturing tolerances acknowledge the fact that dimensional perfection is impossible to achieve. More importantly, from an economic perspective, perfection may be an expensive and inappropriate goal. Unnecessarily small tolerances do not improve quality or performance, they do increase costs. As manufacturing tolerances shrink, production and inspection costs increase rapidly. Properly specified tolerances minimize manufacturing and assembly costs, ensure product performance, and provide a means of assessing and maintaining process controls.
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