The principle of ejector pin design in injection mold involves the use of pins to push or eject the molded part out of the mold cavity. These pins are typically located in the ejector half of the mold and are designed to withstand the forces exerted during ejection.
Here are some key principles to consider when designing ejector pins for injection molds:
1. Pin Diameter: The diameter of the ejector pin should be carefully selected to ensure it can withstand the ejection force without bending or breaking. The pin diameter should be determined based on the material being molded and the size and shape of the part.
2. Pin Length: The length of the ejector pin should be sufficient to fully eject the part from the mold without causing any damage. It should extend beyond the part's surface to avoid interference during ejection.
3. Pin Material: Ejector pins are typically made from hardened steel or other materials with high wear resistance. The material should be selected based on the expected number of mold cycles and the type of material being molded.
4. Pin Placement: The ejector pins should be strategically placed to ensure even ejection of the part from the mold. They should be positioned to avoid any interference with the part or other mold components.
5. Pin Shape: The shape of the ejector pin can vary depending on the part design and ejection requirements. Common shapes include straight, stepped, or tapered pins. The shape should be chosen to minimize any marks or damage on the part during ejection.
6. Ejector System: The ejector pins are usually part of a larger ejector system that includes ejector plates, ejector pins, and return pins. The design of the ejector system should ensure smooth and efficient ejection of the part from the mold.
7. Cooling Considerations: Ejector pins can generate heat during ejection, so proper cooling channels should be incorporated into the mold design to prevent overheating and ensure optimal performance.