Geometrical tolerance transfer for sheet metal forming processes
As an essential link between sheet metal design and manufacturing, process planning generates a sequenced set of instructions to manufacture parts. However, according to a literature survey in this thesis, the tolerance transfer issue in sheet metal forming are insufficiently addressed: machining er...
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Format: | Theses and Dissertations |
Language: | English |
Published: |
2008
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Online Access: | https://hdl.handle.net/10356/14243 |
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Institution: | Nanyang Technological University |
Language: | English |
Summary: | As an essential link between sheet metal design and manufacturing,
process planning generates a sequenced set of instructions to
manufacture parts. However, according to a literature survey in
this thesis, the tolerance transfer issue in sheet metal forming
are insufficiently addressed: machining errors and their causes
are not presented comprehensively as the sources of final error;
only size dimensional tolerances are discussed in detail; computer
aided tolerancing for parts formed by multiple operations jointly
such as bending, punching, and blanking, is seldom studied;
statistical tolerancing are utilized only for sheet metal assembly
issues or size dimensional tolerances, not geometric tolerances. Therefore, according to these problem unaddressed, the presented
research is motivated to explore and to propose systematically
three dimensional geometrical tolerance transfer approaches for
sheet metal part forming. The here proposed models are suitable
for worse case or statistical analysis (using the Monte-Carlo
methods). First, an integrated CAD/CAPP system based on feature
evolvement, associative features, and data association mechanism,
is outlined. Then, a mathematical model of geometric tolerance
transfer is proposed. For Monte Carlo simulations, the
distribution of final errors may not closely follow the normal
distributions. Finally, a machining error-correlated cost model is
presented and applied to tolerance synthesis using a case of
parallelism tolerance. Angular errors are demonstrated to affect
final errors vastly. This tolerance transfer method is applied on parts formed by
bending (parallel and non-parallel) and punching operations
jointly. It can be applied on all bending-like and cutting operations easily and extended to other sheet metal forming operations. The research work is a solid basis for future work in
this area. |
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