Research On Process Of The Thick-walled Parts By Injection Molding

The wall thickness of plastic parts is generally1～4mm, plastic parts of whose wall thickness is more than6mm were generally considered as thick-wall injection molding parts. Wall thickness was suggested smooth and not too thick in product design, but thick-wall injection molding parts are also required in plastic injection due to customer demand, product styling, performance, aesthetics. Compared to ordinary injection molding products, thick-wall injection molding parts demand more on plastic material and injection molding machine,and it can easily cause defects such as dent, shrinkage, warpage, weld lines and cracks.So,how to produce thick-wall injection molding parts with good quality would be the focus of this study.Firstly, take TV transparent pillar for example, volume shrinkage was selected as evaluation of the quality of plastic parts. Mold temperature, melt temperature, injection time, packing pressure, packing time and cooling time are process parameters which affect the quality of injection molded parts. Orthogonal experiment, Moldflow and data processing techniques was used in order to find out the relationship between process parameters and quality of injection molded parts.Secondly, taking square parts of different thickness as the test objects, the relationships between warpage and wall thickness were studied by using crystalline thermoplastics and amorphous thermoplastics in this chapter.The result showed that warpage increased with the increase of wall thickness, wall thickness affected the warpage of crystalline thermoplastics more significantly than it did to the warpage of amorphous thermoplastics and the amount of transverse warping deformation is bigger than the amount of longitudinal warping deformation.Thirdly, based on the theory of overmolding injection, process design, precautions and principles of wall thickness design, two different injection molding programs for TV transparent pillar was disgusted in this chapter,a better experimental results was achieved by using overmolding injection molding program with proper wall thickness selection and process design. This research results was then applied to production.