1402054378

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Unformatted text preview: ocation tolerance, that is centred around each hole’s nominal position. Starting from this statistical method, we introduce a very simple rule in locator configuration that gives quite interesting suboptimal solutions. Keywords: fixture design, 3-2-1 locating principle, holes pattern, location tolerance, statistical positioning 1. INTRODUCTION A machining fixture controls the position and the orientation of the workpiece reference frame with respect to the machine one. The reference frame in a machining fixture is defined by the locators. During machining, the tool path is defined with respect to this workpiece reference frame. Ideally, the locators make point contact with the workpiece and the position and orientation of the workpiece reference frame with respect to the machine one is perfectly accurate. However, in reality the geometry and the position of the locators are imperfect and the reference frame they produce has position and orientation errors with respect to the machine reference frame. This misalignment produces geometrical errors in the features machined on the workpiece, e.g. location error of a holes pattern. The existing research provides essential steps towards the design of locators placement. The more largely used formalism is based on the screw theory due to its compactness and its general applicability [Ohwovoriole et al., 1981]. The screw theory allows to identify both the causes of a wrong positioning of th...
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This note was uploaded on 08/03/2010 for the course DD 1234 taught by Professor Zczxc during the Spring '10 term at Magnolia Bible.

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