Communicating with GD&T

Jan 8, 2025

Hanomi creates 2D drawings from 3D models with the symbolic language Geometric Dimensioning and Tolerancing. GD&T is a system for defining and communicating engineering tolerances through symbols. It is used to define geometry of parts and assemblies: variation in size, form, orientation, and location of individual features. Seeing a design come into fruition is an involved task, one that requires precise communication between engineers/designers and manufacturers. This ongoing conversation between the two parties can end up being quite cyclical if there is ambiguity, so like any good relationship communication is key and can be found in GD&T.

Why does Hanomi use GD&T?

Manufacturers deeply value GD&T because it is extremely detailed allowing for continuous precision, efficiency, and quality:

  1. Enhanced Quality: GD&T ensures that parts meet their intended function, reducing defects and improving overall product reliability.

  2. Reduced Scrap, Rework, and Cost: With precise tolerances and clear inspection criteria, manufacturers can minimize waste and avoid costly rework. The necessary tolerances also prevents over-engineering, which can lead to unnecessary production costs.

    • Inspection: With the proper identification of datum on parts, the inspection team can perform accurate and consistent inspections and measurements. This clarity reduces the potential for errors and inconsistencies during inspection, ensuring that parts meet their design specifications. Consequently, it minimizes the likelihood of rejecting parts that are actually workable, enhancing overall quality control and efficiency in the production process. 

    • Root Cause Analysis Failure: When teams diligently investigate potential causes they often struggle to pinpoint the exact cause. This difficulty can largely be attributed to a lack of understanding and fluency in the technical and mechanical language required to effectively communicate and analyze these factors. Without clear and precise communication, the process of diagnosing and resolving issues becomes significantly more complex, leading to persistent and unresolved problems.

  3. Scalability: GD&T is especially valuable for mass production, where consistency across thousands or millions of parts is critical. Through providing tight tolerances in component production it ensures precision and high-quality output.

    • Interchangeability: Failures in interchangeability can occur due to miscommunication about the functionality of these parts. When the design intent and functional requirements are not clearly communicated or understood, it can lead to mismatched components. This misalignment can result in failures on the assembly line, causing delays, increased costs, and compromised product quality.

  4. Regulatory Compliance: Industries like aerospace and medical devices often mandate the use of GD&T to meet stringent safety and quality standards.

Understanding GD&T

GD&T is based on a set of standardized symbols defined by the ASME Y14.5 standard (American Society of Mechanical Engineers). These symbols communicate specific tolerances and constraints that dictate how parts should be manufactured and inspected. There are five main categories of symbols:

Each symbol works in conjunction with datums—the reference points, lines, or planes from which measurements are taken. Together, these elements create a clear and comprehensive blueprint for manufacturing.