There are many types of gates for daily necessities molds, but regardless of the type, the location of the gate greatly affects the molding performance and quality of the plastic part. Therefore, rationally selecting the gate location is a crucial design step in improving the quality of the plastic part. When selecting the gate location, the flow state of the molten plastic in the mold, filling conditions, and venting conditions should be analyzed based on the geometric characteristics and technical requirements of the plastic manufacturing. The gate should be located at the thickest point of the plastic part's cross-section. When the wall thickness of the plastic part varies significantly, if the gate is located at the thinner wall, the molten plastic will not only face high flow resistance after entering the cavity but will also cool easily, affecting the flow distance and making it difficult to ensure complete filling of the cavity. The thickest part of the plastic part is often where the melt solidifies last. If the gate is located at the thinner wall, the shrinkage of the molten plastic in the thicker area will not be compensated, resulting in surface depressions or shrinkage cavities.
The size and location of the gate should be chosen to avoid jetting and creeping phenomena. If a small mold gate is directly opposite a cavity with a large width and thickness, the high-speed material flow passing through the gate will experience high shear stress, leading to melt fracture phenomena such as jetting and creeping. Sometimes, jetting can also cause wavy flow marks on the plastic part.
The mold gate location should be chosen to minimize the plastic flow path and reduce the number of flow direction changes.
The mold gate location should facilitate the venting of gases from the cavity.
The material flow should be prevented from deforming the cavity, core, and inserts.