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With the development of science and technology, plastic, its density is small, than high strength, dielectric properties, excellent resistance to electrical properties, and will be easy to wear, seismic, chemical resistant and processing advantages of people of all ages, and are widely used in electronic equipment instrumentation, communication tools, agriculture, fisheries, packaging and commodity sectors. One of the most important method of injection molding plastic molding, also got people's attention. After years of research and development, the maturing process, forming out of the products gradually applied to all walks of life. But with the expansion of the scope of application of the plastic parts of the overall performance of the plastic parts a higher demand, especially in the automotive and appliance industry. Weld line as a common injection flaw, not only affect the appearance of the parts, but also seriously reduce the mechanical properties of parts, which restricts the plastic parts in the development of related industries. In order to solve the problems of the weld line, this study explores the following: (1) Analysis of the morphology of the plastic melt flow process, and the formation mechanism of the weld line; same time, a detailed analysis of the morphology and structure of the weld line, and elaborated weld line performance evaluation indicators: the common weld line coefficient FKL quantitative characterization weld marks the extent of damage plastic parts. (2) the experimental study of the process parameters of the thermoplastic plastic products (ABS bar specimen, for example) in the case of yes / no weld marks its mechanical properties investigated, and then through Taguchi method designed experiments on two different thermoplastics (non-crystalline plastic ABS and crystalline plastic PE) for injection molding, weld marks on the mechanical properties of rod specimen, which specifically explore the impact of process parameters on the performance of the weld line. Experiments show that: the non-crystalline plastic ABS injection temperature greatest impact on the performance of the weld line. Crystalline plastic PE, injection pressure weld marks the greatest impact. Eliminating the weld line defects by optimizing the process parameters should first start from the main influencing factors, in order to obtain the best results. (3) three to reduce the weld line defects in the process, especially sequential valve gate technology (SVG), the improvement of weld line. (4) using Moldflow software, simulation and verification experiments to optimize the process parameters. In the simulation of cold slug well the shape of the weld line, prove cold slug wells in the same area of ??different shapes, diamond cold slug well improve the most obvious effect of the weld line. At the same time the new technology SVG technology simulation, to verify the good results in the improvement of weld line.
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