A new concept of active temperature control for an injection molding process using infrared radiation heating

Abstract

This paper deals with an innovative injection molding process that uses infrared radiation heating for active temperature control of the molded polymer. The feasibility of the proposed technique was investigated through numerical simulation and experimental study. By directly heating the molded polymer with radiation energy, precise and rapid temperature control and a small effect on the cooling duration were expected. Zinc‐selenide and a CO2 laser were used as a transparent mold window and radiation energy source, respectively. In the numerical simulation, temperature distribution both in the molded polymer and the mold wall was evaluated for various molding conditions. The results showed that the heating extent of the molded polymer varied with radiation intensity, radiation absorption coefficient, and melt flow rate. It was also estimated that extension of the cooling duration with the present technique was much shorter than that of a conventional conductive heating technique. In the experimental study, the present technique was applied to actively control the melt temperature and to improve the quality of molded products. As a result, apparent reduction of the residual molecular orientation and considerable improvement of the surface transcription were successfully realized.

Rapid thermal cycling of injection molds: An overview on technical approaches and applications

“…Sato and Kurosaki 107 and Saito et al 43 used infrared radiation for mold rapid heating and found that the birefringence in the molded part decreased with the increase in radiation intensity. Kang and coworkers 57 investigated the effects of passive heating on the birefringence distribution of an optical disk.…”

“…Because of high demand of microstructured parts in the fast growing biomedical, optical, and electronics industries, this problem has received considerable attention in the past decade. Most investigations 20,21,24,34,41,43,44,47,57−61,90−93 on mold rapid heating in the past decade were aimed at providing a practical solution to this problem. A general consensus has been reached in the micromolding research community that an elevated mold temperature close to or even above the polymer solidification temperature is a necessity for successful replication of surface micro/nanostructures, particularly with high aspect ratios.…”

“…44,46 In addition to external infrared sources, infrared lamps may be directly installed inside the mold plates. 43 With internal lamps, infrared heat is available when the mold is closed, allowing active heating during the entire mold cycle. The internal infrared source allows both the mold surface and the polymer to be heated during the injection stage.…”

Passive mold temperature control by a hybrid filming-microcellular injection molding processing

“…Usually this kind of inhomogeneity in a product has negative effects on final property. To reduce inhomogeneity in the products, separation of the filling and cooling stage in the injection molding process is the key, which means with high temperature filling and low temperature cooling in a production cycle [3]. Therefore, several techniques based on heat transfer control have been proposed to improve the quality of molded products.…”

Microinjection Molding of Enhanced Thermoplastics

“…This problem could be eventually solved with periodical cleaning of the mould cavity (Chang & Hwang, 2006). Direct infrared radiation heating of polymer inside the cavity has been proposed by Saito et al (2002). As long as CO 2 laser is directed towards the polymer melt through the transparent window in the mould wall, temperature gradient during injection is significantly reduced.…”