Calculation Formula of Positioning Error Based on Three Dimensions and Four Datum

Calculation of positioning error is difficult for engineers because of its invisibility in forming process, as well as coexistence of various forms. This paper is focused on the calculation of fixture location error from the novel direction to deepen understanding of error origination. In contrast to previous investigations, the authors have developed an equation to compute fixture location error based on three dimensions and four datum. This equation which is given after differential operation allows resource of location error. The findings from the differential equation shows that the fixture location error consists of the change in three misalignments of process datum and locating datum, spatula datum and locating datum, locating datum and stop datum respectively under general condition, and the value of fixture location error is gotten after simple operation of their three components listed above. And in case of locating element of plane or (and) Vee block especially, the fixture location error depends on the change in the distance of process datum and spatula datum. The work brings help to analysis positioning error and its conclusion indicates the method to reduce the value of positioning error quickly. (paper)