Development of robust fixture locating layout for machining workpieces

Abstract

A fixture is a device that secures and holds a workpiece to maintain its orientation and position during a manufacturing process, so that the desired workpiece quality can be achieved. Although many researchers have worked on locating accuracy analysis and tolerance analysis towards the automated generation of locating schemes for fixtures, most of them have focused on part localization, while feature errors due to geometrical inaccuracies and dimensional deviations during the mass production are usually neglected. In the current paper, a study on fixture locating layout is carried out with the robust design approach by combining the Taguchi method and the Monte-Carlo statistical method in order to increase the quality of final machining workpieces, so that the layout can be robust and insensitive to the errors. The Taguchi method is employed to study the locating effect of the locator's position at different levels and the Monte-Carlo method is applied to simulate the variation of coordinates of the locating contact points. A case study comprising drilling a hole on a prismatic workpiece is also carried out. The paper shows that the errors on the locators and workpiece have significant effects on the features to be machined and thus these variations should not be ignored.