Software Implications of Material Boundary Modifiers and Under-Constrained Datum Reference Frames on Tolerance Evaluation

Abstract

The assessment of tolerances according to Geometric Dimensioning and Tolerancing principles expressed in the ASME Y14.5 standard has gained widespread acceptance in dimensional metrology. As requirements on the complexity and accuracy of parts increase, combined with the need for inspection software to provide meaningful actual values required for rework and/or statistical process control in addition to simple pass/fail evaluations, defining the criteria for tolerance evaluation becomes a major challenge. This presentation analyzes various combination of material modifiers on datums and their effects on tolerance evaluation. Optimization issues regarding underconstrained datum reference systems and simultaneous requirements on multiple features with varying tolerance zones are also addressed. Several test cases combining these factors are discussed and accordingly best practices are proposed.