• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.31 no.5
• /
• pp.594-600
• /
• 2007

Rapid mold heating has been recent issue to enable the injection molding of thin-walled parts or micro/nano structures. Induction heating is an efficient way to heat a conductive workpiece by means of high-frequency electric current caused by electromagnetic induction. Because the induction heating is a convenient and efficient way of indirect heating, it has various applications such as heat treatment, brazing, welding, melting, and mold heating. The present study covers an experimental investigation on the rapid heating using the induction heating and rapid cooling using a vortex tube in order to eliminate an excessive cycle time increase. Experiments are performed in the case of a steel cup mold core with various heating and cooling conditions. Temperature is measured during heating and cooling time, from which appropriate mold heating and cooling conditions can be obtained.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 2008.10a
• /
• pp.439-443
• /
• 2008

Painting process or coating with acrylic film may improve the surface defects of injection molded parts deteriorated by weldlines. flow marks. and etc. However such processes increase the production costs and increase environmental problems. Recently various types of rapid mold heating & cooling technology have been developed in order to improve surface quality of products. In this study. the heating & cooling performance of a telephone case mold is investigated by heat transfer analysis, in which the rapid mold heating & reeling technology is applied. The surface temperature of the mold was measured using thermal image camera and compared with analysis results. The influence of the rapid mold heating & cooling technology on weldline appearance and cycle time increase was also examined.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 2009.05a
• /
• pp.168-171
• /
• 2009

High-frequency induction is an efficient way to heat mold surface by electromagnetic induction in a non-contact procedure. Though the induction heating has an advantage in terms of its rapid-heating capacity on the mold surface, it still has a restriction on mold temperature control due to geometric restriction of an induction coil according to the mold shape. It has been recently applied to the injection molding of thin-walled parts or micro/nano structures. For localized induction heating, an injection mold composed of ferromagnetic material and paramagnetic material is used. The electromagnetic induction concentrates on the ferromagnetic material, from which we can selectively heat for the local mold elements. The present study proposed a localized induction heating method by means of selective use of mold material. The feasibility of the proposed heating method is investigated through the comparison of experimental observations according to the mold material.

• Proceedings of the KSME Conference
• /
• 2008.11a
• /
• pp.1119-1123
• /
• 2008

High-frequency induction is an efficient way to heat mold surface by electromagnetic induction in a noncontact procedure. It has been recently applied to the injection molding of thin-walled parts or micro/nano structures. Though the induction heating has an advantage in terms of its rapid-heating capacity on the mold surface, it still has difficulty in efficient mold temperature control due to the restriction of an induction coil design suitable for the given mold shape. The present study proposed a localized mold heating method by means of selective use of mold material. For localized induction heating, an injection mold composed of ferromagnetic material and paramagnetic material is used. The electromagnetic induction concentrates on the ferromagnetic material, from which we can selectively heat for the local mold elements. The feasibility of the proposed heating method is investigated through an experimental measurement in terms of the heating efficiency on the localized mold surface.

• Transactions of Materials Processing
• /
• v.19 no.3
• /
• pp.152-159
• /
• 2010

Rapid mold heating has been recent issue to enable the injection molding of thin-walled parts or micro/nano structures. High-frequency induction is an efficient way to heat mold surface by electromagnetic induction in a non-contact manner, and has been recently applied to the injection molding due to its capability of rapid heating and cooling of mold surface. The present study covers a three-dimensional finite element analysis to investigate heating efficiency and structural safety of the induction heating process of an injection mold. To simulate the induction heating process, an integrated simulation method is proposed by effectively connecting an electromagnetic field analysis, a transient heat transfer analysis and a thermal stress analysis. The estimated temperature changes are compared with experimental measurements for various types of induction coil, from which heating efficiency according to the coil shape is discussed. The resulting thermal stress distributions of the mold plate for various types of induction coils are also evaluated and discussed in terms of the structural safety.

• Transactions of Materials Processing
• /
• v.16 no.4 s.94
• /
• pp.229-233
• /
• 2007

The present work focuses on the prediction of birefringence in injection-molded part and its improvement by rapid mold heating. To calculate birefringence, flow-induced residual stress is computed through a fully three-dimensional injection molding analysis. Then the stress-optical law is applied from which the order of birefringence can be evaluated and visualized. The birefringence patterns are predicted for a rectangular plate with a variation of mold temperature, which shows that the amount of molecular orientation and birefringence level decreases with an increase of mold temperature. The effect of mold temperature on the order of birefringence is also studied for a thin-walled rectangular strip, and the relevant results are compared with experimental measurements. Both predicted and experimental patterns of birefringence are in agreements on the observation that the birefringence level diminishes significantly when the mold temperature is raised over the glass transition temperature.

• Transactions of Materials Processing
• /
• v.16 no.2 s.92
• /
• pp.113-119
• /
• 2007

Rapid mold heating has been recent issue to enable the injection molding of thin-walled parts or micro/nano structures. Induction heating is an efficient way to heat material by means of an electric current that is caused to flow through the material or its container by electromagnetic induction. It has various applications such as heat treatment, brazing, welding, melting, and mold heating. The present study covers a finite element analysis of the induction heating process which can rapidly raise mold temperature. To simulate the induction heating process, the electromagnetic field analysis and transient heat transfer analysis are required collectively. In this study, a coupled analysis connecting electromagnetic analysis with heat transfer simulation is carried out. The estimated temperature changes are compared with experimental measurements for various heating conditions.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 2007.05a
• /
• pp.195-198
• /
• 2007

The present work focuses on the prediction of birefringence in injection-molded plastic part and its improvement by rapid mold heating. To calculate birefringence, flow-induced residual stress is computed through a fully three-dimensional injection molding analysis. Then the stress-optical law is applied from which the order of birefringence can be evaluated and visualized. The birefringence patterns are predicted for a rectangular plate with a variation of mold temperatures, which shows that the amount of molecular orientation and birefringence level decreases with an increase of mold temperature. The effect of mold temperature on the order of birefringence is also studied for a thin-walled rectangular strip, and compared with experimental measurements. Both predicted and experimental patterns of birefringence are in agreements on the observation that the birefringence level diminishes significantly when the mold temperature is raised to above the glass transition temperature.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2010.05a
• /
• pp.1237-1238
• /
• 2010

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 2007.05a
• /
• pp.199-204
• /
• 2007

Hot embossing, one of Nanoimprint Lithography(NIL) techniques, has been getting attention as an alternative candidate of next generation patterning technologies by the advantages of simplicity and low cost compared to conventional photolithographies. A typical hot embossing usually, however, takes more than ten minutes for one cycle of the process because of a long thermal cycling. Over the last few years a number of studies have been made to reduce the cycle time for hot embossing or similar patterning processes. The target of this research is to develop an induction heating apparatus for heating a metallic micro patterning mold at very high speed with the large-area uniformity of temperature distribution. It was found that a 0.5 mm-thick nickel mold can be heated from $25^{\circ}C$ to $150^{\circ}C$ within 1.5 seconds with the temperature variation of ${\pm}5^{\circ}C$ in 4-inch diameter area, using the induction heating apparatus.