title: A Model for Geometry-Dependent Errors in Length Artifacts.
abstract: We present a detailed model of dimensional changes in long length artifacts, such as step gauges and ball bars, due to bending under gravity. The comprehensive model is based on evaluation of the gauge points relative to the neutral bending surface. It yields the errors observed when the gauge points are located off the neutral bending surface of a bar or rod but also reveals the significant error associated with out-of-straightness of a bar or rod even if the gauge points are located in the neutral bending surface. For example, one experimental result shows a length change of greater than 1.5 µm on a 1 m ball bar with an out-of-straightness of 0.4 mm. This and other results are in agreement with the model presented in this paper.
authors.affiliation: National Institute of Standards and Technology, Gaithersburg, MD 20899.
authors.forename: Daniel
authors.initials: D
authors.lastname: Sawyer
authors.affiliation: The Boeing Company Seattle, WA 98108.
authors.forename: Brian
authors.initials: B
authors.lastname: Parry
authors.affiliation: National Institute of Standards and Technology, Gaithersburg, MD 20899.
authors.forename: Steven
authors.initials: S
authors.lastname: Phillips
authors.affiliation: National Institute of Standards and Technology, Gaithersburg, MD 20899.
authors.forename: Chris
authors.initials: C
authors.lastname: Blackburn
authors.affiliation: National Institute of Standards and Technology, Gaithersburg, MD 20899.
authors.forename: Bala
authors.initials: B
authors.lastname: Muralikrishnan
keywords: ASME B89.1.12; Coordinate Measuring Machine (CMM); ISO 10360; Step Gauges; ball bars; design of length artifacts; dimensional artifacts; high accuracy length standards; performance evaluation of (CMM)