Influence of Sprue Size on Mechanical Properties of Plastic Products in Design of Injection Mold

doi:10.19491/j.issn.1001-9278.2020.09.010

Abstract

Abstract:

In this paper, a self-designed one?mold four-cavity injection standard mold was employed to fabricate the high-density polyethylene (PE-HD) samples through injection molding with different sprue sizes. By changing the injection molding process parameters such as melt temperature, mold temperature, and injection pressure, the mechanical properties of injection-molded samples including tensile, impact, and bending behaviors were investigated. These samples exhibited a significant improvement in mechanical properties when using the sprue with modified cross?sectional dimensions, and their tensile strength, impact strength, bending strength and bending modulus increased by about 3.40 %, 79.86 %, 18.11 % and 113.36 % in maximum, respectively. The relationship between the injection process parameters and properties was also established. After modification for sprue, the injection-molded sample could be fully filled, and there was no defect like collapse observed. The mold designed by this work has a reasonable overall structural layout after the modification of sprue. This design can provide a useful reference for mold design of test samples with a similar standard.

Key words: injection molding, sprue size, mechanical propertiy, temperature

CLC Number:

TQ320.66⁺2

YE Zhiyin. Influence of Sprue Size on Mechanical Properties of Plastic Products in Design of Injection Mold[J]. China Plastics, 2020, 34(9): 56-60.

Figures/Tables 9

Fig.1. Photos of the cavity surface for the standard sample and the samples

试样类型	试样截面/mm²	修改前截面/mm²	修改后截面/mm²
拉伸试样	81.96	4.35	32.78
冲击试样	40.46	4.35	16.73
弯曲试样	43.99	4.35	16.36

Tab.1. Cross section area of each specimen and pouring port before and after modification

Fig.2. Schematic diagram of standard samples injected from the small pouring port

Fig.3. Injection molding standard impact specimens before the modification of the pouring port

Fig.4. Schematic diagram of standard samples injected from the modified pouring port

Fig.5. Injection molding standard impact specimens after the modification of the pouring port

Fig. 6. Tensile strength of the samples before and after pouring port modification

Fig.7. Impact strength of the samples before and after pouring port modification

Fig.8. Bending properties of the samples before and after pouring port modification

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