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TECHNICAL PAPERS

Geometric Reasoning on Molding Planning for Multishot Mold Design

[+] Author and Article Information
Zhou-Ping Yin1

School of Mechanical Science and Engineering, Huazhong University of Science and Technology, Wuhan, P. R. Chinayinzhp@mail.hust.edu.cn

Han Ding

School of Mechanical Science and Engineering, Huazhong University of Science and Technology, Wuhan, P. R. China and School of Mechanical Engineering, Shanghai Jiaotong University, Shanghai, P. R. China

You-Lun Xiong

School of Mechanical Science and Engineering, Huazhong University of Science and Technology, Wuhan, P. R. China

1

Corresponding author.

J. Comput. Inf. Sci. Eng 6(3), 241-251 (May 29, 2006) (11 pages) doi:10.1115/1.2218362 History: Received September 20, 2005; Revised May 29, 2006

This paper presents algorithms for automated design of multishot molds for manufacturing multimaterial or multicolor objects, and focuses on molding planning that determines a sequence of mold stages required to produce the desired object. By modeling a multimaterial object as an assembly of homogenous components, a geometric reasoning approach is proposed to generate feasible or practical mold stage sequences by combining the assembly planning approach and the two-plate mold design method. First, a graph-based assembly model, namely the attributed contact graph, is derived from the B-rep models of the constituent components of the gross object by detecting and representing all the contacts between mating components explicitly. Then, all feasible mold stage sequences, represented by an AND/OR graph, are generated by reasoning on geometric constraints due to the demoldability and connectedness requirements using an assembly-by-disassembly strategy. Depending on its demoldability, each component is to be made by one of the three basic molding strategies with varied mold stages and/or mold pieces. To narrow the choice, an optimal or practical molding plan is searched from the feasible molding plans according to some criteria such as the number of mold stages, the number of side cores, and flatness of the parting line. Finally, starting from the last mold stage, mold pieces for each mold stage of the selected molding plan are constructed recursively. The feasibility of the proposed algorithms is demonstrated through an implemented prototypical system, which has been tested successfully with various multi-material objects.

FIGURES IN THIS ARTICLE
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Copyright © 2006 by American Society of Mechanical Engineers
Topics: Molding , Design , Algorithms
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Figures

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Figure 1

Schematized rotary platen molding process: (a) after first shot; (b) after rotation; (c) after second shot; and (d) a two-material object to be molded

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Figure 2

Overview of the proposed approach for a multishot mold design

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Figure 5

A three-stage mold generated for manufacturing the object shown in Fig. 4: (a) the third stage mold pieces; (b) the second stage mold pieces; and (c) the first stage mold pieces

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Figure 6

The main steps of generating mold piece for the object shown in Fig. 4: (a) the gross mold and its parting direction; (b) the parting line and surface generated

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Figure 7

The two-stage mold generated for manufacturing a two-material valve: (a) the first mold stage; (b) the second mold stage

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Figure 8

The three-stage mold generated for manufacturing a three-color mobile phone house: (a) the first mold stage; (b) the second mold stage; and (c) the third mold stage

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Figure 3

Point-plane contacts: (a) the definition of a point-plane contact; (b) contacts between two polyhedra expressed as point-plane contacts

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Figure 4

A simple three-material object: (a) the CAD models of its constitute components; (b) its attributed contact graph; (c) its feasible molding plans representing as an AND/OR graph, and (d) a practical molding plan for the object

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