Interpreting the Language of GD&T in Metrology

摘要

With more outsourcing and complex supply chains, defining and communicating the design intent of parts through Geometric Dimensioning and Tolerancing (GD&T) is becoming even more important. The industrial world is continuing its adoption of Geometric Dimensioning and Tolerancing (GD&T), the advanced tolerancing methodology. The symbolic language is intended to be both more precise while providing more latitude in allowable variations, replacing the simpler method of adding tolerances to each dimension. "Basically GD&T is a language of symbology," explained Rob Jensen, Dimensional Standards Compliance Manager of Hexagon Metrology (North Kingstown, RI). Each of its 14 symbols has a unique purpose and definition, specified in a 'feature control frame' with specific modifiers and datum references. Like a language, the grammar that ties the symbols GD&T and modifiers together is important. Measurement and quality programs need to use GD&T to measure parts and ensure they meet design intent. With a well-defined language, a designer or manufacturer should interpret each feature control frame the same. However, that is usually the problem.