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TECHNICAL PAPERS

Prediction of Local Part-Mold and Ejection Force in Injection Molding

[+] Author and Article Information
Omar M. Bataineh

Department of Industrial Engineering, Jordan University of Science and Technology, Irbid 22110, Jordan

Barney E. Klamecki

Department of Mechanical Engineering,  University of Minnesota—Twin Cities, Minneapolis, MN 55455-0111

J. Manuf. Sci. Eng 127(3), 598-604 (Dec 01, 2004) (7 pages) doi:10.1115/1.1951785 History: Received July 18, 2004; Revised December 01, 2004

A numerical simulation system was developed to predict local part-mold forces and local and total ejection forces in injection molding. Local reaction forces between the part and mold surfaces are calculated first using numerical molding process and structural simulations. Using experimentally obtained coefficients of friction the friction force and ejection force are calculated. Ring moldings were used to measure the coefficient of friction. Box moldings were used to validate predictions of local and total ejection forces and to demonstrate the use of the system in mold design. Calculated ejection force was maximum at the beginning of ejection and differed by 10%–16% from experimental values, with the difference being much less over the main part of the ejection process. The maximum number of ejector pins for failed ejection was predicted. The difference between the predicted and observed number of ejector pins was at most four pins for a twenty ejector pin system.

FIGURES IN THIS ARTICLE
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Copyright © 2005 by American Society of Mechanical Engineers
Topics: Force , Friction , Molding
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References

Figures

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Figure 1

Forces acting during part ejection

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Figure 3

Ejection force vs time for a PC ring molding

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Figure 4

Nodal displacements during ejection of a box molding

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Figure 5

Boundary conditions during ejection of the box molding

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Figure 6

Predicted shape of a PP box molding

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Figure 7

Actual warpage of a PP box molding

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Figure 8

Measured ejection forces vs time for a PE box molding

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Figure 9

Measured and predicted ejection force for a PE box molding

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Figure 10

Equivalent stress distribution in a PE molding for ejection with 20 ejector pins

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Figure 11

Tensile yield stress vs sample temperature

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Figure 12

Equivalent stress distribution in a PE molding for ejection with 16 ejector pins

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Figure 2

Dimensions of a ring molded over a core

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