An Examination of the Effect of Variationin Datum Targets Location on Part Acceptance

摘要

The use of datum targets within Geometric Dimensioning and Tolerancing (GD&T) is commonplace in industryrntoday. Datum targets are used primarily for manufacturing and inspection setups where it is impractical to employrndatum simulators. An examination of the effect of the location and variation of secondary and tertiary datum targetsrnis made using both mathematical analysis and simulation. It is found that the location and variation of datum targetsrnthemselves have a profound effect on the measured location of holes referencing those datums. Explanation andrnvalidation for accepted practice are found and some additional basic guidelines are developed for the placement ofrnsecondary and tertiary datum targets relative to hole patterns.