The stages of injection molding for plastic parts include several crucial phases, each impacting the final product's quality and dimensional accuracy.
The process begins with the Filling Stage, where molten plastic is injected into the mold cavity until it's approximately 95% full. This phase can be performed at high or low speeds, with each approach having its own impact on the material's flow and the final part's properties. High-speed filling benefits from shear thinning of the plastic, reducing overall flow resistance and potentially thinning the solidified layer near the mold's surface. Low-speed filling, on the other hand, emphasizes thermal conduction control, leading to a thicker solidified layer and increased flow resistance due to slower thermal conduction and less viscous heating.
Holding Pressure Stage follows, maintaining pressure to compact the molten plastic and compensate for material shrinkage. This phase ensures that the cavity remains filled, the part density increases, and the part's dimensions are maintained as the material cools and solidifies.
The Cooling Stage is where the part solidifies sufficiently to be ejected without deformation. This stage is critical for determining the cycle time and the part's final properties, with the cooling system's design playing a vital role in the efficiency and uniformity of the cooling process.
Finally, the Ejection Stage marks the end of the cycle, where the cooled and solidified part is removed from the mold. Proper ejection mechanism design is essential to prevent damage or deformation of the part during this final process step.
Each stage is interconnected, requiring precise control and optimization to ensure the production of high-quality injection molded parts.