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TECHNICAL BRIEF

Experimental Study of Demolding Properties on Stereolithography Tooling

[+] Author and Article Information
Chao-Chyun An

Department of Mechanical Engineering,  National Chiao Tung University, 1001 Ta Hsueh Road, Hsinchu 30010, Taiwan, R.O.C.

Ren-Haw Chen

Department of Mechanical Engineering,  National Chiao Tung University, 1001 Ta Hsueh Road, Hsinchu 30010, Taiwan, R.O.C.chenrh@mail.nctu.edu.tw

J. Manuf. Sci. Eng 129(4), 843-847 (Nov 02, 2006) (5 pages) doi:10.1115/1.2716752 History: Received March 18, 2006; Revised November 02, 2006

Direct tooling using stereolithography (SL) photopolymer has been developed as rapid tooling for short-run injection molds. However, the tool strength, thermal conductivity, and erosion resistance of SL mold are lower than that of the conventional metal mold. Previous study has showed that the tool life was limited under 200 shots and tool damage often occurs during part ejection. In this paper, experimental data from a demolding properties test are presented and discussed. The experiments were performed using various cooling time, hold pressure, and mold temperature. The experimental data were analyzed by measuring demolding force and surface roughness to evaluate tool life and failure mechanism in order to obtain a working range for the process parameters. The test result shows that the demolding force has close relation with cooling time and mold temperature.

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Copyright © 2007 by American Society of Mechanical Engineers
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Figures

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Figure 1

Experimental setup: (a) Compression test fixture and (b) hot press machine with the compression fixture

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Figure 2

Flowchart of the molding procedure

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Figure 3

Effect of hold pressure on the demolding stress, under the conditions, hold time = 5s, cooling time=180s, mold temperature=50°C

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Figure 4

Effect of hold time on the demolding stress at hold pressures of 5MPa, 10MPa, and 20MPa, under the conditions, cooling time=180s, mold temperature=50°C

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Figure 5

Demolding stress against mold temperature under the conditions, hold pressure=10MPa, hold time=5s, cooling time=180s

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Figure 6

Effect of cooling time on the demolding stress under the conditions, hold pressure=10MPa, hold time=5s, mold temperature =50°C

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Figure 7

Compressive stress-strain curves of SL epoxy at various temperatures

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Figure 8

Comparisons of demolding stress and yield stress of SL mold material with temperature: variation of the ratio of demolding stress to yield stress

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Figure 9

(a) Peeling of the mold wall surface and (b) roughening of the mold wall surface

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Figure 10

Demolding times versus surface roughness of SL mold (hold pressure=10MPa, hold time=5s, mold temperature =50°C)

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Figure 11

Effect of cooling time on the ratio of demolding stress to yield of an SL mold (hold pressure=10MPa, hold time=5s, mold temperature =50°C)

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Figure 12

Method for fixing SL mold plate onto the mold base (C: area of resistance to demolding force)

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