AN UNCERTAINTY ANALYSIS METHOD FOR COORDINATE REFERENCING IN MANUFACTURING SYSTEMS

Accurate and consistent transformations between design and manufacturi ng coordinate systems are essential for high quality part production. Fixturing and coordinate measurement are common coordinate referencing techniques which are used to locate points or measurement points on w orkpiece reference surfaces to establish these coordinate transformati ons. However, uncertainty sources such as geometric form deviations in workpiece surfaces, tolerances on fixture locators, and errors in coo rdinate measurements exist. A result is that coordinate transformation s established using the locating and measurement points are in herentl y uncertain. An uncertainty analysis method for coordinate referencing is presented in this paper. The uncertainty interval concept is used to describe essential characteristics of uncertainty sources in coordi nate referencing and coordinate transformation relationships. The meth od is applied to estimating uncertainties in simple and compound coord inate transformation obtained using coordinate referencing in an exper imental mold manufacturing system. Results of Monte Carlo simulations are used to show that The uncertainty analysis method gives a consiste nt and high percentage of coverage in evaluating coordinate referencin g in the examples studied.