• Elastomers and Composites
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• v.48 no.4
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• pp.300-305
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• 2013

Part shrinkage in injection molding is inevitable phenomenon. Thus, it is necessary not only study on the reducing part shrinkage but characterization of part shrinkage. In this study, part shrinkage in injection molded 2.5 dimensional annular shaped specimens has been studied using glass fiber reinforced PC. Annular shaped specimens were designed with various sizes of outer diameter and thickness. Injection temperature, packing time and packing pressure were selected for operational conditions. Profile variations of outer and inner diameters of molded specimens for various operational conditions were investigated. Sizes of outer and inner diameters of injection molded specimens were smaller than the sizes of mold. Part shrinkage decreased as outer diameter and thickness increased. Part shrinkage showed anisotropic behavior and it depended upon gate location. Subsequently, molded specimens were not circular but oval in shape, and showed the largest shrinkage in the direction of gate. It was realized that the mold design such as gate design is important to control the shape of molded products.

• Design & Manufacturing
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• v.15 no.2
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• pp.36-41
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• 2021

The 3 dimensional Pipe (Annular) Shaped Products was selected as a test sample, then a attribute of a molding shrinkage according to the parameters of a injection process was examined with PC, which is the typical engineering plastic. Both the inside and the outside diameter of the Pipe (Annular) sample were shrank into the inner direction of the part. And then the comparative analysis of the samples proved that a increasing thickness led a bigger shrinkage rate in the equal outside diametric samples, and a decreasing outside diameter caused a bigger shrinkage rate in the same thickness samples. The comparative study of the cushion volume of a injection machine showed that the molding shrinkage was most affected by the pressure strength among the resin temperature, the maintenance pressure strength and the maintenance pressure duration time. Each of the shrinkage rates according to the measuring direction and the gate position was different. As a result, the injection molded sample had not a typical circular shape.

• Journal of the Korean Society of Combustion
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• v.4 no.1
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• pp.49-57
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• 1999

An experimental study on double-concentric diffusion flame has been carried out in order to investigate the shape, the flame length, and the other characteristics of the flame. Flow visualization of the flame by the $TiO_2$ particles and also the emission measurements are conducted. The commercial grade LP gases are used as fuel. The inverse diffusion flames are formed at the center when the central air flow rate is about 0.1 L/min. With a larger flow rate of the central air jet than 0.2 L/min the flame turns to be an annular-shaped flame, which is very bright. When the central air flow rate increases over 2.4 L/min, the flame turns to blue and the flame tips are opened because of the lifting of the inner part of the flame. Because of this lifting and the incomplete combustion, the CO emission increases abruptly from 25 ppm to more than 150 ppm. On the contrary, the NOx emission is decreased.