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Ultrasonic thermoforming of a large thermoplastic polyurethane film with the aid of infrared heating

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Abstract

This study concerns ultrasonic thermoforming of Thermoplastic polyurethane (TPU) film for the fabrication of a television speaker diaphragm. The speaker diaphragm has a convex-protruded feature with a rounded-rectangular shape on which a number of micro-corrugations are formed for sound quality improvement. This diaphragm has generally been manufactured out of thin TPU film using a thermoforming process, which required cycle time as long as several minutes for proper heating and cooling of the polymer film and mold. In this study, an ultrasonic thermoforming process was introduced to reduce the cycle time to fabricate the diaphragm by taking advantage of the rapid and localized heating capability of ultrasonic vibration energy. To improve the forming quality of a large diaphragm for a television speaker, infrared heating was added to the process to preheat the TPU film before the forming stage. Various processing parameters including ultrasonic thermoforming and infrared heating conditions were investigated in relation to the forming quality. As a consequence, the diaphragm could be fabricated with acceptable forming ratios (> 95 % in the band region and > 70 % in the micro-corrugations) and short cycle time (12 s). This means that the proposed process is superior to conventional thermoforming processes that require long cycle time (> 200 s).

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Authors and Affiliations

  1. Department of Mechanical System Design Engineering, Seoul National University Science and Technology, Seoul, 01811, Korea

    Hyun-Joong Lee, Dong-Ju Shin & Keun Park

Authors
  1. Hyun-Joong Lee
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  2. Dong-Ju Shin
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  3. Keun Park
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Corresponding author

Correspondence to Keun Park.

Additional information

Hyun-Joong Lee is a Ph.D. candidate in the Department of Mechanical Design and Robot Engineering at Seoul National University of Science and Technology, Korea. He received his B.S. and M.S. degrees from Seoul National University of Science and Technology, in 2013 and 2015, respectively. His current research includes ultrasonic fabrications of polymer parts including ultrasonic imprinting and ultrasonic thermoforming processes.

Keun Park received his B.S. and M.S. degrees in Precision Engineering and Mechatronics from KAIST, Korea, in 1992 and 1994, respectively. He then received his Ph.D. degree in Mechanical Engineering from KAIST in 1999. Dr. Park is currently a Professor of the Department of Mechanical System Design Engineering at Seoul National University of Science and Technology, Korea. His research interests include numerical analysis of material forming processes, micro-fabrication, and additive manufacturing.

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Lee, HJ., Shin, DJ. & Park, K. Ultrasonic thermoforming of a large thermoplastic polyurethane film with the aid of infrared heating. J Mech Sci Technol 31, 5687–5693 (2017). https://doi.org/10.1007/s12206-017-1109-x

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  • DOI: https://doi.org/10.1007/s12206-017-1109-x

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