A methodology for applying V–blocks and clamps to non–prismatic workpart fixtures

Abstract

Most research in computer–aided fixture design (CAFD) aims to develop algorithms to automatically design the fixture configuration of workpieces. Due to the complexity of non–prismatic geometry, the application domain has been mostly limited to prismatic workpiece fixturing. Moreover, based on the 3–2–1 locating principle, the locators employed are mostly restricted to the cylindrical type. This research focuses on another type of fixture configuration for non–prismatic parts that has been mostly overlooked. This is to apply V–blocks in workholding to ensure stable and efficient work setup of non–prismatic parts. The algorithm presented in this paper determines V–block locating by utilising projected geometric reasoning. The major steps of the algorithm include candidate–point generation, angle and distance checking, co–ordinate transformation, and interference analysis. Further more, this paper also explores another algorithm for determining the corresponding clamping location of the V–block. The horizontal clamp is planned based on static principles. To ensure workpiece stability, the planning procedure is classified into three distinct cases according to the force distribution and frictional conditions at the contacting regions. These two algorithms, V–block locating and clamp planning, are applied interactively to obtain the most desired fixture configuration. Finally, an example is provided to explain how these algorithms are applied.