Determination of key workpiece product characteristics in a machining fixture using uncertainty analysis and loss cost function implementation

Abstract

The study of fixture related errors is playing an increasingly important role in the improvement of machined part quality. In this work, the locator variability of machining fixtures is analyzed following an uncertainty approach, allowing us to estimate the effect of fixture related geometrical errors on key product characteristics of machined workpieces. Monte Carlo simulation was implemented to generate sufficient variability to determine the expected value of the measuring points of the machined workpiece surface and its related key product characteristic. The results from the Monte Carlo simulation allow sufficient range of values to construct a mathematical relationship between fixture related errors and machined workpiece key product characteristics. Furthermore, the Taguchi loss function is used to investigate the loss cost incurred by a given fixturing uncertainty scheme. An example problem of a prismatic workpiece is presented, where the locating error due to the fixturing system is evaluated in order to know its influence on the workpiece flatness and its associated uncertainty.