Composition of the die casting mold push rod ejection mechanism
The die-casting mold ejector mechanism is the core device for ejecting castings from the mold. Its components must work together to ensure efficient and smooth removal of the casting from the mold cavity. This mechanism primarily consists of key components such as the ejector, ejector retaining plate, ejector plate, guide pins and sleeves, and a reset mechanism. Each component performs a distinct function during the ejection process, collectively ensuring accurate and reliable ejection.
As the component that directly contacts the casting and applies thrust, the push rod’s material selection and structural design directly impact the demolding effect. High-strength alloy steel, such as SKD61, is typically used. After heat treatment, it possesses sufficient hardness and wear resistance to withstand the wear and tear caused by repeated ejection. The push rod’s diameter and length must be calculated based on the structural characteristics of the casting and the required demolding force. For example, large castings require a larger diameter push rod to disperse the thrust and avoid deformation. For complex cavities, the push rod must precisely match the cavity shape to ensure even thrust transmission.
The push rod mounting plate and push plate are key components that support and secure the push rod. They are connected by screws to form an integral push rod assembly. The push rod mounting plate must be machined with mounting holes that match the push rod diameter, with hole positioning accuracy within 0.01mm to prevent the push rod from deflecting or binding during movement. The push plate is connected to the mold’s ejection power unit, such as a hydraulic cylinder or mechanical ejector. Its flatness requirements are high, and it typically undergoes grinding to ensure even force transmission under load, preventing bending or breakage of the push rod due to excessive localized stress.
The guide pin and sleeve assembly guides the ejection mechanism, ensuring smooth movement of the push rod in the desired direction. The guide pin is typically cylindrical and chrome-plated to reduce friction. The guide sleeve is constructed of wear-resistant material and precisely fits the guide pin, with a clearance of 0.005-0.01mm. During design, the guide pins and sleeves are symmetrically positioned on either side of the ejector plate to ensure balanced forces during ejection and prevent interference between the push rod and the cavity wall due to misaligned guidance, which could damage the mold or casting.
The reset device returns the ejector mechanism to its initial position after demolding, preparing it for the next die-casting cycle. Common reset devices include a reset spring and a reset rod. The reset spring is typically installed between the ejector plate and the mold’s movable die base, levering its elastic force to achieve automatic reset. The reset rod, in contact with the mold’s fixed die, pushes the ejector plate back into position during mold closing, ensuring accurate reset. Furthermore, some complex molds are equipped with limiters, such as limit pins, to restrict the ejector plate’s maximum ejection distance, preventing damage to components caused by excessive ejection.
