Research Papers

A Methodology for Creating Shape Rules During Product Design

[+] Author and Article Information
Adam Oster

 University of Idaho, Moscow, ID 83844oste1400@vandas.uidaho.edu

Jay McCormack

 University of Idaho, Moscow, ID 83844mccormack@uidaho.edu

J. Mech. Des 133(6), 061007 (Jun 16, 2011) (12 pages) doi:10.1115/1.4004195 History: Received October 05, 2010; Revised April 28, 2011; Published June 16, 2011; Online June 16, 2011

Shape grammars provide the means to represent the physical embodiment of a class of products in a set of generative rules. Once developed, the shape grammar can be used to generate new forms through automated synthesis or interaction by one or more designers. Creating the shape rules has been most often performed after the design process by examining existing designs. Furthermore, the approach to create a set of rules from an existing set of products was usually an ad hoc process of generalizing form, identifying feature options, and classifying logical subdivisions of the complete product geometry. This paper proposes a more explicit method of shape grammar creation, that is, aligned with well-known design methodologies in order to enable the creation of a shape grammar during the new product development process. The established methodology for function first design and design exploration provides many of the requisite steps for creating a shape grammar, connecting customer requirements and constraints to product form and provides a skeleton onto which a rule creation approach is mapped. An example is included in which the proposed methodology is used to create a shape grammar that represents the internal components of a bladeless slurry pump in order to support design exploration driven by simulation and experimentation.

Copyright © 2011 by American Society of Mechanical Engineers
Topics: Design , Pumps , Shapes
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Figure 1

An example of a shape grammar rule, the headlight design that it was used to produce, and an actual vehicle headlight

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Figure 2

A shape rule and shape in which the rule can be applied

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Figure 3

Instances of shape A in shape C are shown in bold (from Fig. 2)

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Figure 4

Designs in the language defined by the initial shape and rule in Fig. 2

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Figure 5

A shape rules that adds a gear to an identified shaft

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Figure 20

Rule 5 in the grammar adds additional discs to the pump

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Figure 19

Rule 4 in the shape grammar adds the first disc to the shaft

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Figure 18

Rule 3 in the shape grammar that creates and positions the stepped shaft

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Figure 15

The sequence of design decision-making that can be represented by the shape grammar. For this pump, the details of the ball type thrust bearing, mechanical shaft seal, stepped shaft, and discs are explored (shown in gray)

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Figure 14

The initial shape includes a coordinate system and constraints

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Figure 13

A rough layout of the hierarchy elements identified in Fig. 1 and explored in Table 4

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Figure 12

The shapes for (a) the ball type thrust bearings, (b) the mechanical seals, (c) the stepped shaft, and (d) the disc

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Figure 11

Hierarchical chart of modules, component types, and functions

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Figure 10

Aggregate function structure of the pump that addresses the list of requirements in Table 2 as well as the three primary functional modules in the pump

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Figure 9

Activity diagram of the bladeless pump

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Figure 6

The hierarchy of functions, component types, modules, and the overall product function

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Figure 8

A rule derived from the hierarchy of design alternatives in Fig. 7 to add and position the geometry of design alternative x

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Figure 24

The grammatical representation of the pump was used to generate (a) the CAD representation of the pump and (b) the pump operating on a sand slurry

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Figure 23

Rule 8 in the grammar adds holes to a disc in pump

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Figure 22

Rule 7 in the grammar adds holes to a disc in pump

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Figure 21

Rule 6 in the grammar creates and positions a labyrinth type seal

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Figure 17

Rule 2 in the shape grammar creates and positions the mechanical shaft seal with respect to the bearings

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Figure 16

Rule 1 in the shape grammar creates and positions ball type thrust bearings

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Figure 7

The tree of design decision-making where siblings are alternatives from the morphological chart



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