OFF-LINE PLANNING AND SIMULATION OF AN INTELLIGENT FIXTURING SYSTEM FOR HIGH-PRECISION MACHINING

Abstract

Fixtures are indispensable tools used in machining, assembly, inspection and other manufacturing operations. The functions of fixtures are to locate and secure the workpiece in proper orientation and position, so that the manufacturing process can be carried out to meet design specifications. In the past decades, extensive research on various fixturing issues has primarily focused on fixture planning such as automatic generation of suitable fixture elements and fixture layout or creation of advanced hardware to increase the flexibility while accommodating a variety of part types. As to the fixturing process which concerns appropriate location and clamping functions of the fixture to firmly hold the part being machined in the desired position during the entire machining process, it is a relatively unexplored area. The present research aims to contribute to this operation or execution stage of the fixturing system with regard to the strategies, models, and formulations specific to the fixturing process. In this thesis, an Intelligent Fixturing System (IFS) is proposed to adaptively adjust the clamping intensities to achieve minimum deformation of the workpiece according to the cutter position and the cutting forces during machining. Since adaptive clamping forces appropriate to the dynamic machining environment are provided, the proposed IFS offers higher quality of machined parts and more flexibility to disturbances. Based on the mechanism and requirement analysis, the architecture of the IFS is presented. To realize the on-line control of the clamping intensities during machining, a model-based control scheme is proposed. Two key components of this control scheme, the fixture-workpiece model and the optimization model, are then derived. Finally an offline simulation approach is applied to evaluate and verify the proposed IFS. The simulation results show that the developed fixturing system is able to improve the part accuracy without changing the fixturing configuration.