The deformation, bending and twisting of injection molded products


The deformation, bending and twisting of injection mold […]

The deformation, bending and twisting of injection molded products are mainly caused by the fact that the shrinkage rate of the flow direction during plastic molding is larger than that of the vertical direction, so that the shrinkage ratio of the parts is different and warped, and it is inevitable in the injection molding. There is a large internal stress remaining inside the piece to cause warpage, which is a manifestation of deformation caused by high stress orientation. Therefore, fundamentally speaking, the mold design determines the warping tendency of the part. It is very difficult to suppress this tendency by changing the molding conditions. Finally, the problem must be solved from the mold design and improvement.

Melting, silver, cracked polystyrene, transparent parts of plexiglass, sometimes through the light can see some sparkling filament-like silver. These silver streaks are also known as spots or cracks. This is because the stress in the vertical direction of the tensile stress is generated, and the weight of the polymer molecule is expressed by the heavy flow orientation and the difference in the folding rate of the unoriented portion.

Under normal circumstances, the gloss of the surface of an injection molded part is mainly determined by the type of plastic, the colorant and the finish of the mold surface. However, due to some other reasons, the surface color and gloss defects of the product and the dark color of the surface are often caused.

The molten plastic in the cavity meets in the form of multiple strands due to the intrusion of the insert holes, the discontinuous flow rate, and the region where the filling flow is interrupted, and a linear weld seam is produced because it cannot be completely fused. In addition, in the case of gate injection molding, a welded joint is formed, and the strength at the welded joint is poor.