IMProVe 2011 - Proceedings

Integrated Product and Process Design
Shape Similarity: Methods and Industrial Applications
D. Francia (a), A. Ceruti (a), G. Caligiana (a), A. Liverani (a)
(a) University of Bologna
Abstract:
Mass production, reduced production investment, reduced response time and variability,
globalization and increased customization are the most responsible for the need of
optimizing the manufacturing process. As companies provide higher levels of
customization, the number of products offered increases. Minimizing the cost of providing
variety is possible by exploiting shape similarities amongst parts and products. Another
reason for utilization of similarity assessment is the cost estimation. Total cost of any part
to machine results from material costs, setup costs, tooling costs, and operation costs.
Furthermore in very small productions the total cost of new components is affected more
than 70% by process planning and CAM (Computer Aided Manufacturing) programming. A
relevant part of this time may be saved by modifying the process plan of an old similar
part and this is a well known practice in the manufacturing industry.
Shape similarity search in a CAD system is an answer to reduce process plan preparation
because it finds similarities in geometry by extracting shape signatures from the 3D
models and then comparing these signatures exploiting distance functions. This paper
presents a review of the methods adopted to generate shape signatures and an analysis of
the distance functions suitable for the comparison. The first part of this work investigates
the models commonly proposed to extract the shape signature from a solid part. The
second part of the paper discusses the choice of the distance function. At the end of this
discussion the most appropriate method is proposed to assess the shape similarity, once
the part to be manufactured has been assigned: results are shown in terms of accuracy of
comparison and computational time, seeking for a trade-off between them.
Keywords: Shape Similarity, Computer Aided Design, Computer Aided Manufacturing,
Standardization
Corresponding Author: Daniela Francia
Tel.: +39.051.2093352
Fax.: +39.051.2093412
e-mail: d.francia@unibo.it
Address: v.le Risorgimento, 2, 40137 Bologna.
June 15 th – 17 th , 2011, Venice, Italy
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IMProVe 2011 - Proceedings