In the production process of precision injection molds, residual gas is a common and critical problem that requires careful attention and resolution. Residual gas not only affects the appearance of the product, leading to defects such as gas marks and scorching on the surface, but also adversely impacts the internal structure, reducing the product's mechanical properties. Therefore, optimizing the venting system to reduce residual gas is crucial for precision injection molds.
The design of the venting system is fundamental to optimization. In precision injection molds, the layout of venting channels needs careful planning. Typically, venting channels should be located on the mold parting surface, especially in areas where the melt is last filled and at the ends of the cavity. This is because during injection molding, gas is often compressed into these areas along with the melt flow; venting channels at these critical locations allow for timely and effective gas removal. Simultaneously, the direction of the venting channels should match the melt flow direction to ensure smooth gas discharge and prevent gas accumulation inside the mold.
Controlling the dimensions of the venting channels is also a key aspect of optimizing the venting system. For precision injection molds, the depth and width of the venting channels need precise control. Excessively deep venting channels may cause molten metal to overflow during filling, forming flash and affecting the dimensional accuracy and appearance quality of the product. Conversely, shallow venting channels cannot effectively expel gas, leaving residual gas. Generally, the depth of the venting channel should be determined based on the characteristics of the plastic material used. For materials with good flowability, the venting channel depth can be appropriately shallow; for materials with poor flowability, the venting channel depth needs to be appropriately increased. The width of the venting channel also needs to be set reasonably. Too wide a channel will waste mold material and increase mold costs, while too narrow a channel will affect the venting effect.
Besides venting channels, vent plugs are also commonly used components in precision injection mold venting systems. Venting plugs are usually installed in appropriate positions in the mold core or cavity, and their function is to expel gas through their own tiny gaps. When selecting vent plugs, their material and size need to be considered. The material should have good wear resistance and corrosion resistance to ensure that it will not be damaged or blocked during long-term use. Regarding size, it should be selected according to the specific structure of the mold and venting requirements to ensure that the vent plug can effectively expel gas without obstructing the filling of the molten metal.
The sealing performance of the mold significantly impacts the effectiveness of the venting system. Poor mold sealing allows outside air to enter during injection molding, mixing with gases in the melt and increasing the difficulty of removing residual gas. Therefore, the design and manufacturing of precision injection molds must ensure precise fit between all mold components and employ appropriate sealing structures and materials to prevent air intrusion.
The setting of injection molding process parameters also needs to be coordinated with the optimization of the venting system. For example, parameters such as injection speed, injection pressure, and holding time all affect gas venting. Excessively fast injection speeds may result in gas being trapped inside the melt; excessively high injection pressures may compress the gas, making it difficult to escape; and excessively short holding times may cause gas to regenerate during product cooling. Therefore, continuous experimentation and adjustment are necessary to find the most suitable injection molding process parameters to optimize the venting system and reduce residual gas.
Regular maintenance and cleaning of the precision injection mold's venting system are also essential. Over long-term use, venting channels and plugs may become clogged with plastic debris and impurities, affecting venting efficiency. Therefore, it is necessary to regularly disassemble and clean the mold, check the integrity of all components of the venting system, and replace any damaged parts promptly to ensure that the venting system is always in good working order. Through these optimization measures, residual gas in the precision injection mold can be effectively reduced, improving product quality and production efficiency.
