Hindawi Publishing Corporation Advances in Mechanical Engineering Volume 2013, Article ID 282906, 10 pages http://dx.doi.org/10.1155/2013/282906 Research Article Gas-Assisted Heating Technology for High Aspect Ratio Microstructure Injection Molding Shia-Chung Chen, 1,2,3 Chen-Yang Lin, 1 Jen-An Chang, 1,2,3 and Pham Son Minh 1,2,3,4 1 Department of Mechanical Engineering, Chung Yuan Christian University, Chung-Li 32023, Taiwan 2 R&D Center for Membrane Technology, Chung Yuan Christian University, Chung-Li 32023, Taiwan 3 R&D Center for Mold and Molding Technology, Chung Yuan Christian University, Chung-Li 32023, Taiwan 4 Faculty of High Quality Training, University of Technical Education, Ho Chi Minh City 70000, Vietnam Correspondence should be addressed to Shia-Chung Chen; shiachun@cycu.edu.tw Received 28 June 2013; Accepted 26 August 2013 Academic Editor: Lei Zhang Copyright © 2013 Shia-Chung Chen et al. Tis is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. A hot gas is used for heating the cavity surface of a mold. Diferent mold gap sizes were designed. Te mold surface temperature was heated to above the glass transition temperature of the plastic material, and the mold then closed for melt flling. Te cavity surface can be heated to 130 ∘ C to assist the melt flling of the microfeatures. Results show that hot gas heating can improve the flling process and achieve 91% of the high aspect ratio microgrooves (about 640.38 m of the maximum of 700 m). Te mold gap size strongly afects the heating speed and heating uniformity. Without surface preheating, the center rib is the highest. When the heating target temperature is 90 ∘ C or 100 ∘ C, the three microribs have a good uniformity of height. However, when the target temperature exceeds 100 ∘ C, the lef side rib is higher than the other ribs. 1. Introduction Nowadays, injection molding is one of the most widely used processing technologies in the manufacture of plastic prod- ucts. Among typical molding parameters, the mold surface temperature is critical. At higher mold surface temperatures, the surface quality of the part will improve [1, 2]. In the injection molding feld, microinjection molding is used to manufacture a variety of polymer components, because of its low cost and potential for high-volume production. Most applications are in the feld of microoptics (such as CDs and DVDs) and microfuidic devices. Production of other molded microoptical components including optical gratings, optical switches, and waveguides [3–5] as well as a variety of molded microfuidic devices including pumps, capillary analysis systems, and lab-on-a-chip applications [6, 7] is ongoing. In general, to improve an injection molding part, it requires higher mold temperatures during injection to mini- mize part thickness and injection pressure. However, main- taining high mold temperature during the flling process and lowering the mold temperature to below the defection temperature during the postflling process, while avoiding great increases in cycle time and energy consumption, is not easy. To address this problem, a variety of dynamic mold temperature controls (DMTC) have been explored in recent years. Teir purpose is to eliminate the frozen layer, ideally producing a hot mold during the flling stage and a cold mold for cooling. Te most inexpensive way to achieve high mold temperature is to use cooling water at temperatures as high as 90 ∘ C or 100 ∘ C[8]. Local mold heating using an electric heater [9] is some- times used to assist high mold temperature control. However, this requires additional design and tool costs. Further, electri- cal heating is usually used as auxiliary heating and is limited to increases in mold temperature of roughly several tens of degrees centigrade. Mold surface heating, such as induction heating [10–12], high-frequency proximity heating [13, 14], and gas-assisted mold temperature control (GMTC) [15, 16], can provide sufcient heating rates without signifcant increases in cycle time. In recent years, we have conducted systematic study of