The position design of the guide pins and guide sleeves of the injection molding push rod fixing plate is the core link to ensure the stable operation of the ejection mechanism, which is directly related to the accuracy of product demolding and the service life of the mold. During the opening and closing process of the mold, the push rod fixing plate needs to move along a precise trajectory to avoid bending or breaking of the push rod or scratches on the surface of the product due to offset. The position of the guide pins and guide sleeves must be consistent with the force center of the ejection mechanism. They are usually symmetrically distributed based on the geometric center of the push rod fixing plate to ensure uniform force. For example, for a rectangular push rod fixing plate, the guide pins and guide sleeves can be set at a diagonal position to form a stable support structure; for a circular fixing plate, an equal angle distribution can be adopted to ensure consistent guiding accuracy in all directions during the ejection process.
Position design also needs to consider coordination with other mold components to avoid spatial interference with parts such as push rods, reset rods, and springs. When determining the mounting hole positions for guide pins and guide sleeves, the layout dimensions of each part must be accurately calculated to ensure that the centerline of the guide pin is parallel to the motion trajectory of the push rod and reset rod, and that the spacing meets assembly requirements. For example, the distance between the guide pin and the push rod should be greater than 1.5 times the sum of their diameters to prevent friction or collision during movement. At the same time, the position of the guide pin and guide sleeve must avoid the cooling water channels and exhaust grooves of the mold to avoid affecting the cooling efficiency and exhaust effect of the mold, thereby ensuring the molding quality of the product.
Controlling the positional accuracy of guide pins and guide sleeves is a key design parameter, including coaxiality, parallelism, and perpendicularity. Excessive coaxiality errors can cause the guide pins and guide sleeves to fit too tightly, resulting in jamming or wear; insufficient parallelism can cause the push rod retaining plate to tilt during movement, affecting ejection accuracy. Therefore, strict form and position tolerances must be noted during design. For example, the coaxiality tolerance of the guide pin and guide sleeve should be controlled within 0.01mm, and the perpendicularity tolerance with the push rod retaining plate should not exceed 0.02mm/100mm. During the processing process, a precision boring machine or jig grinder can be used to ensure that the positional accuracy of the mounting holes meets the design requirements. At the same time, the guiding performance is verified through a test run after assembly, and adjustments or repairs are made if necessary.
Positioning design also needs to consider mold maintenance convenience. The guide pins and guide sleeves should be installed in a location that allows for easy removal and replacement to avoid increased mold downtime due to maintenance difficulties. For example, the guide pins can be fixed to the mold base using a stepped structure, while the guide sleeves are embedded in the mounting holes of the push rod fixing plate and secured with bolts or an interference fit. This ensures a secure connection and facilitates later replacement. Furthermore, the guide pins and guide sleeves should be located in the non-working area of the mold to avoid contact with the product or other components of the injection molding machine. This reduces external interference with the guide mechanism and improves mold operation stability.
In molds with specialized structures, the positioning of guide pins and guide sleeves requires targeted optimization. For example, for molds for large or complex products, multiple sets of guide pins and guide sleeves can be used to enhance guiding stability. For molds where the core pulling mechanism is linked to the ejection mechanism, the position of the guide pins and guide sleeves must be coordinated with the core pulling trajectory to avoid motion interference. After the design is completed, motion simulation is performed using 3D modeling software to simulate the motion trajectory of the push rod retaining plate during the mold opening and closing process. This allows for verification of the proper positioning of the guide pins and guide sleeves, identifying and correcting potential issues promptly to ensure stable and reliable mold operation during production.
