| This experimental study concerns local injection molding shrinkage measurements. Injection molding is a process where a polymer resin is injected under pressure in a closed cavity. Shrinkage is the concept dealing with differences in dimension between an injected part and its mold.; Injection molding shrinkage of a polypropylene is studied under three aspects. First, the effects of the position on parallel to flow and cross flow shrinkage are observed. A constant thickness plate is used and local shrinkages are measured. Second, the effects of some molding parameters (holding pressure and injection velocity) are found using a statistical design of experiment. Finally, the third aspect studied is the geometry of the mold. Three geometries are compared in term of shrinkage: The constant thickness plate, a plate with a thinner, symmetrically restrained shrinkage area and a plate with asymmetrically restrained shrinkage. The prevailing observed effects are shrinkage anisotropy, mold geometry, local distribution and finally parameters effects. (Abstract shortened by UMI.)... |
