Injection molding molds consist of various components, each serving a specific function in the injected molded plastic part production process. Let’s explore the key components of an injection molding mold and their functions:
Cavity and Core
Although the types of injection moulding are not the same. But the mold always consists of two halves, the cavity and core, which fit together to create the mold cavity. The cavity defines the outer surface of the part, while the core shapes the inner surface. These components are usually made of hardened steel or other durable materials to withstand the high pressures and temperatures involved in the molding process.
Runner System
The runner system channels the molten plastic from the injection unit of the molding machine into the mold cavity. It typically consists of a sprue, which connects the machine nozzle to the mold, and a network of channels that distribute the plastic to the various cavities. The design of the runner system affects factors such as flow rate, pressure, and material distribution.
Mold Gate
The gate is the entry point through which the molten plastic enters the mold cavity from the runner system. It controls the flow and direction of the material. Common gate types include sprue gate, edge gate, pin gate, and hot runner systems. The gate size and location are crucial for achieving proper filling of the cavity and minimizing defects.
Cooling System
The cooling system is a network of channels or passages within the mold that facilitate the removal of heat from the molten plastic, allowing it to solidify and cool. Efficient cooling is essential for achieving dimensional stability, reducing cycle time, and preventing part warping. Cooling channels are strategically placed near the cavity walls and core to ensure uniform cooling throughout the part.
Ejector System
The ejector system is responsible for pushing the solidified part out of the mold once it has cooled and hardened. It typically consists of ejector pins or plates, which move into the mold to push the part from the cavity. Proper ejection mechanisms are essential to avoid part damage or deformation during the ejection process.
Venting
Venting is the process of allowing air or gases to escape from the mold cavity during injection. It prevents air traps and ensures that the cavity is adequately filled with molten plastic. Venting can be achieved through small channels or vents strategically placed in the mold to release air without affecting the part’s quality.
Guide Pins and Bushings
These components provide alignment and support for the two halves of the mold. Guide pins ensure proper alignment and prevent misalignment during mold closure, while bushings help guide the movement of the mold halves.
Lifters
Lifters are used to create undercuts or features that cannot be formed by a straight-pull mold design. These components help remove the part from the mold by providing additional movement or slides to release the undercut features.
These are the primary components of an injection molding mold and their respective functions. Each component plays a critical role in the overall molding process, ensuring the production of high-quality plastic parts with accurate dimensions, surface finish, and structural integrity.