**Mold Precision Design:** Mold cavity dimensions must be calculated precisely by adding the estimated shrinkage rate to the dimensions of the plastic product. Shrinkage is closely related to factors such as gate type, gate location and distribution, the crystallization orientation (anisotropy) of engineering plastics, the product's shape and size, and the distance from the gate; it is also influenced by the mold's cooling system layout. For instance, with precision injection-molded parts requiring complex shapes and high dimensional accuracy, manufacturing tolerances for the mold cavity must be controlled within ±0.005 mm, and surface roughness must reach Ra 0.1–0.05 μm to ensure the part's high precision.
**Gate Design:** Gate type and location significantly impact the quality of injection-molded parts; common gate types include pin-point gates, side gates, and submarine (tunnel) gates. Pin-point gates are suitable for precision parts requiring high aesthetic quality and dimensional accuracy; they allow for automatic gate detachment and leave minimal gate marks, though they entail higher flow resistance and require higher injection pressure. Side gates are easy to machine and suitable for a wide range of products, but designers must carefully consider gate location and size to avoid defects such as weld lines and jetting marks. Submarine gates are concealed within the mold, preserving the product's appearance, and are commonly used for small precision parts. Gate placement should ensure uniform filling of the mold cavity with the plastic melt, preventing issues like flow imbalance or trapped air; for example, with circular products, the gate can be positioned at the center to ensure the melt flows evenly outward in all directions.
**Cooling System Design:** Mold temperature has a major impact on molding shrinkage; the mold must be maintained within a specified temperature range that remains stable over time, and temperature differences between cavities in multi-cavity molds must be minimized. The cooling system design must ensure uniform cooling to prevent product deformation caused by uneven temperature distribution. Typically, circulating water cooling is employed, with cooling channels distributed evenly around the cavities to maintain stable water flow velocity and volume. For large, precision injection molds, zoned cooling can be employed to adjust cooling water flow rates and temperatures based on the heat distribution across different sections; for instance, in areas with thicker walls or concentrated heat, the number of cooling channels or the water flow velocity can be increased to enhance cooling efficiency and minimize shrinkage-induced deformation.