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TECHNICAL PAPERS

A Preliminary Study of Sealing and Heat Transfer Performance of Conformal Channels and Cooling Fins in Laminated Tooling

[+] Author and Article Information
Seungryeol Yoo

School of Mechanical Engineering, Korea University of Technology and Education, Chonan, Chungnam 330-708, Korea

Daniel F. Walczyk

Department of Mechanical, Aerospace, & Nuclear Engineering, Rensselaer Polytechnic Institute, Troy, New York 12180

J. Manuf. Sci. Eng 129(2), 388-399 (Oct 01, 2006) (12 pages) doi:10.1115/1.2515522 History: Received December 30, 2005; Revised October 01, 2006

Rapid tooling (RT) methods allow for almost complete flexibility in routing of conformal cooling or heating channels within a mold for enhanced thermal control, but tool size is currently limited. A notable exception is the profiled edge laminae (PEL) method, which is a thick-layer laminated RT method intended for large-scale tooling applications. One of the biggest design issues with incorporating conformal channels in a PEL tool is to effectively seal the channels rapidly and inexpensively. Prior attempts in the literature at sealing laminated tools using diffusion bonding or brazing have been just the opposite. Recognizing that many manufacturing applications requiring large-scale tools (e.g., thermoforming, composites forming) do not need the temperature resistance and strength of either diffusion bonded or brazed laminae, this paper investigates alternative sealing methods. It is shown through a preliminary experimental study that (i) manual application of high-temperature adhesives locally around conformal channel holes will effectively seal channels for working fluid temperatures and pressures typically encountered in thermoforming over an extended period of time, and (ii) heating and cooling performance is similar to that of a continuous tool. Localized sealing is actually an advantage when tool porosity is needed. In addition, a novel approach to incorporating cooling fins into the nonforming side of a PEL tool is demonstrated, but thermal performance is poor as compared to conformal channel cooling. Finally, it is shown that simple one-dimensional analytical models can be used to effectively predict tool performance if a conformal channel cell design methodology is used.

Copyright © 2007 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

Illustrations of (a) an unclamped PEL tool, (b) fixturing (e.g., for cutting) and registration scheme for individual lamina, and (c) section view showing piecewise continuous nature of a PEL tool

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Figure 2

Example of a PEL thermoforming mold with three conformal channel circuits

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Figure 3

(a) Cross-sectional view of a conformal channel in a section of a PEL tool, (b) thermally isolated lamina not in direct contact with a conformal channel, and (c) CAD diagram of a bolted PEL test mold with a single conformal channel and held together with four tension rods

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Figure 4

Lamina dimensions (in millimeters) for (a) hole size A, (b) hole size B, and (c) tube trough used for conventional method

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Figure 5

Sealing methods shown for test molds: (a) S1 with gasket film, (b) S2 with adhesive applied around channel hole, (c) S3 showing how adhesive distributes after assembly, and (d) S5 with a thick layer of thermally conductive paste between the tube and mold hole

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Figure 6

(a) Actual test mold S6 and (b) cross-sectional view of the conventional method (note: scaled drawing of trough shown in Fig. 4)

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Figure 7

(a) Leakage testing experimental apparatus and (b) leakage in test mold S4

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Figure 8

Schematic drawing of the test mold used for conformal channel heating experiments

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Figure 9

Experimental setup for assessing conformal channel heating performance

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Figure 10

Side and end schematic views of the test mold used for conformal channel cooling experiments

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Figure 11

Experimental setup for assessing conformal channel cooling performance

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Figure 12

(a) PEL test mold with a vertical array of cooling fins and (b) dimensions of individual lamina (in millimeters)

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Figure 13

Experimental setup for convective air cooling with a fin array

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Figure 14

Air velocity distribution across the fin array

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Figure 15

Top surface temperatures measured for conformal channel cooling experiments

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Figure 16

Top surface temperatures measured for conformal channel heating experiments

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Figure 17

Time versus mold temperature plot of conformal channel heating from test mold S2 (actual) and theoretical model

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Figure 18

Time versus mold temperature plot of conformal channel cooling from test mold S2 (actual) and theoretical model

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Figure 19

Time versus mold temperature plot of convective air cooling from test mold S7 (actual) and theoretical model

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Figure 20

Time versus mold temperature plot of convective air cooling from test mold S2 (actual) and theoretical model

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Figure 21

Sketch of the energy flows in an individual cooling/heating cell of a thermoforming mold with (a) conformal channel heating, (b) conformal channel cooling, and (c) convective fin cooling. Note that the variable used for mold width in the horizontal direction is (w) in all three cases.

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