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Research Papers

Numerical Simulation Assisted Curve Compensation in Compression Molding of High Precision Aspherical Glass Lenses

[+] Author and Article Information
Fei Wang, Fritz Klocke, Guido Pongs

 Fraunhofer Institute for Production Technology IPT, Steinbachstr. 17, 52074 Aachen, Germany

Yang Chen

Department of Industrial, Welding and Systems Engineering, The Ohio State University, 210 Baker Systems, 1971 Neil Avenue, Columbus, OH 43210

Allen Y. Yi1

Department of Industrial, Welding and Systems Engineering, The Ohio State University, 210 Baker Systems, 1971 Neil Avenue, Columbus, OH 43210yi.71@osu.edu

1

Corresponding author.

J. Manuf. Sci. Eng 131(1), 011014 (Jan 23, 2009) (6 pages) doi:10.1115/1.3063652 History: Received October 02, 2007; Revised November 26, 2008; Published January 23, 2009

Compression molding is an effective high volume and net-shape fabrication method for aspherical lenses and precision glass optical components in general. Geometrical deviation (or curve change as often referred to in industry) incurred during heating, molding, and cooling processes is a critically important manufacturing quality parameter. In the compression glass molding process, there are many factors that could lead to curve change in final products, such as thermal expansion, stress and structural relaxation, and inhomogeneous temperature distribution inside the molding machine. In this research, an integrated numerical simulation scheme was developed to predict curve change in molded glass aspherical lenses. The geometrical deviation in the final lens shape was analyzed using both an experimental approach and a numerical simulation with a finite element method program. Specifically, numerical simulation was compared with experimental results to validate the proposed manufacturing approach. The measurements showed that the difference between numerical simulation and experimental results was less than 2μm. Based on the comparison, the mold curve was revised using numerical simulation in order to produce more accurate lens shapes. The glass lenses molded using the compensated molds showed a much better agreement with the design value than the lenses molded without compensation. It has been demonstrated in this research that numerical simulation can be used to predict the final geometrical shape of compression molded precision glass components. This research provided an opportunity for optical manufacturers to achieve a lower production cost and a shorter cycle time.

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Copyright © 2009 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

Schematic of a glass molding cycle

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Figure 2

Generalized Maxwell model for modeling the viscoelastic behavior

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Figure 3

A cross sectional view showing the mechanic load, movement, and contact in the glass molding process

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Figure 4

Heat transfer model of the glass molding process

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Figure 5

Lens molding process conditions: (a) lower mold position versus time and (b) molding temperature and load versus time

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Figure 6

Numerical simulation algorithm for the glass molding process

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Figure 7

Flowchart of the integrated simulation and optimization system

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Figure 8

Comparison of shape geometric deviation between simulation and measurement results after the molding process for a B270 glass

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Figure 9

Deviation of simulated molded glass lens and the compensation value based on numerical simulation

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Figure 10

Deviation of molded glass lens after mold compensation

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