Fixtures are used to constrain workpieces during machining processes. Fixtures locate and hold the workpiece in position and ensure that it is in a state of equilibrium, and that dimensional accuracy is maintained throughout the manufacturing operation. Traditionally, design and manufacturing problems were solved by means of a sequence of design and planning stages followed by manufacturing. However, the recent emergence of Concurrent Engineering has prompted companies to solve the problems in parallel. The availability of data in a concurrent engineering environment places great emphasis on process planning. Fixture planning being part of process planning therefore becomes one of the most important aspects of Concurrent Engineering. The decline in the number of experienced fixture designers, the long lead time for traditional manual design, the rapid progress in the field of Computer Aided Engineering as well as the introduction of Concurrent Engineering are some of the main factors which have motivated researchers to develop automated fixture design systems in recent years. This thesis reports on the development and implementation of FixPlan. FixPlan is a fixture planning system that consists of three separate modules; a Featured Based Design System (FBDS), a Geometric Reasoner (GR), a Fixture Planner (FP). The FBDS module allows the engineer to design components with features such as blanks, holes and pockets. The GR module enables the system to interrogate and analyse the product model and is used extensively by both the FBDS and FP modules. The FP module generates and sequences the set-ups required, selects the positioning, supporting and clamping faces as well as their corresponding points and select the appropriate fixture element of each of the points. Geometrical relationships between features in the product model are used to determine the number of set-ups required as well as their sequence. FixPlan demonstrates the possibility of automating the fixture planning processes and its interrogation with other process planning systems. The main strength of FixPlan lies in its ability to interrogate and analyse the product model through the use of geometric reasoning. The system is unique as it utilises a fully embedded 3D solid modelling representation of the parts to enable spatial reasoning functions.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:643130 |
| Date | January 1997 |
| Creators | Chia, Ser Chong |
| Publisher | University of Edinburgh |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://hdl.handle.net/1842/13372 |
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